Model Boat Mayhem
Mess Deck: General Section => Chit-Chat => Topic started by: justboatonic on August 29, 2010, 11:36:56 am
-
The much vaunted Kepler mission continues to provide evidence that our solar system is tending towards uniqueness rather than the norm.
Prior to Kepler's launch, virtually every exoplanetary system and exoplanets, were hot jupiters. That is, massive planets the size of jupiter or larger and, orbiting their parent star in a matter of days since they were so close to it.
Simulations have shown that where a hot jupiter planet exists very close to its parent star, it must have migrated in from further out. Hot jupiters cannot form close in to a star as there just isnt enough material for them to form. Instead, they must form further out in a system where there is more gas, elements and material required to form planets of their size.
The simulations show where hot jupiters migrate inwards, smaller terrestrial sized planets, if they existed in the system, would be ejected from that solar system.
http://www.telegraph.co.uk/science/space/7966992/Three-vast-planets-found-orbiting-distant-star.html
-
Re: "our solar system is tending towards uniqueness rather than the norm"
Yes that does increasingly seem to be the considered opinion amongst astronomers.
Obviously the universe it a big place but of the know planetary systems, most have vary large planets.
-
Again, I'm not so sure that this is the case. Here's why:
Kepler is attempting to spot planets transitting across the disks of distant stars. From Kepler, all the target stars occupy less than a pixel on the ccd. That is, we can't resolve the disks. The software records the brightness of the target stars' pixel against time, and a dip in the brightness corresponds to a transit. A typical dip is about a 1/10000th drop in brightness, and a transit lasts for just a few hours.
Now, to be long-term-stable, multiple planets orbit their stars in a more-or-less 2d plane. Since a planetary system's orbital plane can lie at any angle relative to Kepler, it is only a tiny fraction of the 100000 target stars that Kepler's monitoring, that will display any transits. Think about the dynamics here, and you'll see that transits are more likely to be seen in those systems where the planets are large (they might just clip the edge of the target star), and more likely to be seen at all when they orbit close to the target star (there's a better chance of a transit) - this is exactly the same bias for those hot-Jupiter systems that have been reported from previous doppler studies.
That said, Kepler's only just got going. There's another three years or so of observations to be made (disregarding any mission extension), a length of time that would (if the angles are right) eventually spot a planet in a Mars-like orbit, and allow for repeated observations of a planet in an Earth-like orbit.
So, over time, Kepler might well discover more Sun-like systems, but in these early days, hot Jupiters are more likely.
Andy, taking off his astronomy hat.
-
...
The simulations show where hot jupiters migrate inwards, smaller terrestrial sized planets, if they existed in the system, would be ejected from that solar system.
...
Mandell and Sigurdsson would disagree with you - Mandell, Raymond and Sigurdsson (2007) refers http://iopscience.iop.org/0004-637X/660/1/823/70644.text.html
Their simulations find that, rather than ejection, resonant shepherding occurs, with accretion at the relevent Legrange points. Note the comment under 3.4 - Final Configurations:
"... Potentially habitable planets survive in almost all of the simulations. In the eight simulations with drag, seven planets larger than 0.2 M (including two in simulation JSD-4) formed in the habitable zone, the orbital region where the stellar flux is sufficient to maintain liquid water on the surface of a planet (assumed to lie between 0.8 and 1.5 AU for these simulations; Kasting et al. 1993). Five planets with masses from 0.13 to 0.4 M formed in the habitable zone in the four simulations without drag..."
In the Conclusion the suggestion is made that our system may have evolved after an earlier Hot Jupiter transit phase, and suggestions are made for further work which may reveal this.
-
Mandell and Sigurdsson would disagree with you - Mandell, Raymond and Sigurdsson (2007) refers http://iopscience.iop.org/0004-637X/660/1/823/70644.text.html
Their simulations find that, rather than ejection, resonant shepherding occurs, with accretion at the relevent Legrange points. Note the comment under 3.4 - Final Configurations:
"... Potentially habitable planets survive in almost all of the simulations. In the eight simulations with drag, seven planets larger than 0.2 M (including two in simulation JSD-4) formed in the habitable zone, the orbital region where the stellar flux is sufficient to maintain liquid water on the surface of a planet (assumed to lie between 0.8 and 1.5 AU for these simulations; Kasting et al. 1993). Five planets with masses from 0.13 to 0.4 M formed in the habitable zone in the four simulations without drag..."
In the Conclusion the suggestion is made that our system may have evolved after an earlier Hot Jupiter transit phase, and suggestions are made for further work which may reveal this.
Dodgy: you've done it again! Most erudite, and completely incomprehensible to us little earth-worms. I'm obviously going to have to give you a promotion from "a lowly legal clerk".
I was going to ask if you would put your post into a language that this particular primitive mammal could understand, but I'm a bit scared that you may (using only words) reduce my mentality to that of an amoeba. BY.
-
I was going to ask if you would put your post into a language ....
hear -> obey!
It's reasonably straightforward. When cheap computer time started to become available to scientists, one thing they did quite early on was orbital simulations - projecting planetary orbits into the future. originally, Newton had provided the basic maths for this, which famously predicted a giant stable clockwork system going on to infinity. Given that history, it was quite a surprise to find that, if you allowed for various eccentricities, the planets could actually move about quite a bit, and many configurations were not stable over several billion years. Here is an example of the sort of thing which can come out of these simulations:
http://www.theregister.co.uk/2009/06/11/boffins_track_odds_of_planetary_smashup/
When we started looking for extraterrestrial planets the easiest ones to find were big ones close to their sun - these shade the sun well and cause it to wobble more than a small planet further away would. We were surprised to find quite a lot of these big, close-to-sun planets - our understanding of the Solar System suggested that big planets formed further away. But orbit simulations found that big planets could move nearer (planetary migration) - and that this could throw the smaller, nearer planets completely out of their system. It was suggested that, because of this mechanism, small watery planets might be very rare, making life as we know it rare as well.
I have referenced a simulation where the big planets move nearer to the sun, but the smaller planets are not ejected, and, indeed, a lot of water ice and dust coalesces in the big planets wakes - building water-rich earth-sized planets in the habitable zone.
Of course all these simulations may be right or wrong - different assumptions produce different results. Computer models frequently bear little relationship to the truth. But it is far too early to say that one model or another MUST be right. This is a science in its infancy - we are only just managing to see the biggest planets around other stars, and I believe that to say that because we have only seen big planets smaller ones cannot exist is theorising well in advance of the observed facts....
-
Now why couldn't you have said that in the first place instead of giving me an incipient migraine? Thank you. Now I think I understand.
Being au-fait with celestial navigation doesn't quite cover those sort of astronomical mathematics. In fact, I actually learned a lot from Bill Brysons' "Short History Of Nearly Everything"! Thanks. BY.
-
Is there any valid or sensible reason for the idea that our system might be the "norm" in the first place? Apart from Star Trek and the Hitch-hikers Guide to the Galaxy and the Clangers and similar erudite scientific thinking?
-
Is there any valid or sensible reason for the idea that our system might be the "norm" in the first place?
Well, it's the only one that we've been able to examine, so we can understand how it evolved. So we go looking for similar planets - we even refer to the part of the Solar System that we live in as the 'habitable zone'. The only form of life we know is protoplasmic, so we go looking for that as well.
The point is that we could probably recognise our kind of planet and our kind of life. If there were gas or dust-particle based intelligences living in interstellar space, or electro-magnetic based intelligences living inside stars we would probably be completely unable to recognise them. That might make it difficult to get a research grant...
-
Different people have different opinions. However, the question of hot jupiters ejecting terrestrial placed planets is dependent on when the hot jupiter forms and how quickly it migrates closer to its star through the stellar disk. If the migration occurs during the first million years or so, the planetary disk, planetesimals have time to reform. If later, well hasta lavista baby!
http://casa.colorado.edu/~raymonsn/hotjup.pdf
"The survival rate of terrestrial planets depends on the rate of migration (faster migration means higher survival rate) and ranges from 15–40% (Mandell and Sigurdsson, 2003)." and "Only a very small fraction (1–4%) of terrestrial planets survive the migration event without significant alteration to their orbits."
So, in any event, the end result is a system that doesnt resemble ours.
The reason, originally, that our solar system was normal was based on, our solar system! It has an average star. Not too big and not too small. It had 9 now 8 planets and in the absence of anything else, was just considered the 'norm.'
as I've said before, the evidence mounts almost daily, that our solar system isnt the norm. Kepler should find many terrestrial sized planets but, although early in its mission, the suggestion is that of a lot of further planets found, the small ones are very close to their star.
Cannot lay my hands on the relevant link yet but, in a test of hot jupiter migration, 2500 simulations resulted in the terrestrial planets being ejected from the system.
-
Different people have different opinions. However, the question of hot jupiters ejecting terrestrial placed planets is dependent on when the hot jupiter forms and how quickly it migrates closer to its star through the stellar disk. If the migration occurs during the first million years or so, the planetary disk, planetesimals have time to reform. If later, well hasta lavista baby!
http://casa.colorado.edu/~raymonsn/hotjup.pdf
"The survival rate of terrestrial planets depends on the rate of migration (faster migration means higher survival rate) and ranges from 15–40% (Mandell and Sigurdsson, 2003)." and "Only a very small fraction (1–4%) of terrestrial planets survive the migration event without significant alteration to their orbits."
Umm, Umm and thrice Umm...
Why do you cite this paper? It strongly supports the idea that earth-like planets can form in the presence of a hot jupiter, which, I understand, you do not believe. Look at its conclusions:
"..based on the above arguments, we expect that terrestrial planets can form in a standard bottom-up fashion in the presence of a hot jupiter, and survive for the lifetime of the parent star...
We have argued that terrestrial planets can form in the presence of hot jupiters. we have shown that potentially habitable planets can form in such conditions. ...
...we suggest that stars with hot jupiters may be a good place to look for extra-solar terrestrial planets....Our result, that potentially habitable planets can exist around stars with hot jupiters, effectively widens the Galactic Habitable Zone...."
The background to these papers is that there is a bit of a problem seeing how earth-like planets can form. When a disc of material round a sun solidifies, there should be a lot of iron in the earth-type orbits, then rock, and all the gas and water should be further out. So an earth-position planet should be mainly made of iron.
If a giant planet from further out migrates inwards, and eventually falls into the star, this migration will stir up the ingredients. Specifically, it will bring water and gas inwards and eject some of the internal iron. So you end up with earth-type habitable planets, made of a mix of iron, rock, gas and water, in a liquid-water zone.
All large planets eject mass from a system. That is not an issue. In fact, outer gas giants eject more mass. From your paper:
"An outer giant planet ejects approximately one half of the total terrestrial mass in the system, while a hot jupiter can remove up to one third of the total mass."
What matters is the mix of materials left. You will note that the paper I cited earlier suggested that our solar system might have experienced an earlier migrating giant planet, a suggestion which this paper also supports. In fact, migrating gas giants may be the norm, and it may be that habitable planets composed of an iron core with a rocky outside and water on the surface can only form in this way.
So, in any event, the end result is a system that doesnt resemble ours.
as I've said before, the evidence mounts almost daily, that our solar system isnt the norm. Kepler should find many terrestrial sized planets but, although early in its mission, the suggestion is that of a lot of further planets found, the small ones are very close to their star.
The paper you have cited is in agreement with Mandell, Raymond and Sigurdsson (2007) ( http://iopscience.iop.org/0004-637X/660/1/823/70644.text.html ) which says:
"If planetary systems that suffer the migration of a gas giant to small distances can eventually form terrestrial planets similar to those in our own system, and the migration of young giant planets is a common result of interactions with the gaseous disk, then it is appropriate to consider the possibility that our own planetary system could have formed earlier generations of giant planets prior to those in the outer solar system.
It is early days yet, as I have often said, but it looks to me as if the migrating hot jupiter theory provides a good explanation of how inner habitable planets can be formed, and may well be the norm for our kind of system....
-
Just as an aside, I wonder why it is that Humankind are so hellbent on trying to discover life as we know it on other planets.
For eons we human have looked towards the stars and wondered how it might be if there may actually exist planets abundantly sustained with the same air that we breathe, the same foodstuffs that we eat, etc, etc. Already we are sending unmanned probes into the heavens, and likewise, already we are being told that the possibility of another planet capable if sustaining human life is pretty much a foregone conclusion.
So what is the deal with this ongoing obsession of trying to colonise other planets which doesn't even belong to us? The question is, what would we do if we were indeed to stumble upon such a life-sustaining planet? And how would WE, the human race, how would we feel if we knew that any particular lifeform from some distant galaxy were intent upon doing the very same thing as us? Could we be trusted not to make the same mess of things as we have to planet Earth. Or indeed, could any alien lifeform be trusted not to make a mess of things once they have found their way here?
Most humans don't even greet their next-door neighbours' with a cheery "Good morning". Indeed, most humans don't even have the foggiest idea of how their neighbours look like. So how in watney would we react should we ever be greeted with a form from a far-distant planet? Or how are we to be trusted, giving that most humans are bent on screwing-up what should be a perfectly good planet anyway? Would our first contact with alien life be a bit of a shocker should it turn out that aliens have the same average mentality of an X-Factor contestant?
-
I think I'm rather pleased that this discussion has descended down to the level of the "Red Tops".
But although I subscribe to the notion that "it's in our genes" to search for and push the boundaries of knowledge, I've come to the conclusion that the entire study and search for extra-terrestrial life (as we know it) is a waste of time and money.
When distances are measured in terms of light years we don't even know if what we are seeing still exists, never mind communicating with anybody.
I'm all in favour of attempting to discover more about the actual cosmos and the extent of the Universe and so on, but I really do believe that we should at least try to understand our own bit of rock a lot better than we do at present. BY.
-
Umm, Umm and thrice Umm...
Why do you cite this paper? It strongly supports the idea that earth-like planets can form in the presence of a hot jupiter, which, I understand, you do not believe. Look at its conclusions:
"..based on the above arguments, we expect that terrestrial planets can form in a standard bottom-up fashion in the presence of a hot jupiter, and survive for the lifetime of the parent star...
We have argued that terrestrial planets can form in the presence of hot jupiters. we have shown that potentially habitable planets can form in such conditions. ...
...we suggest that stars with hot jupiters may be a good place to look for extra-solar terrestrial planets....Our result, that potentially habitable planets can exist around stars with hot jupiters, effectively widens the Galactic Habitable Zone...."
The background to these papers is that there is a bit of a problem seeing how earth-like planets can form. When a disc of material round a sun solidifies, there should be a lot of iron in the earth-type orbits, then rock, and all the gas and water should be further out. So an earth-position planet should be mainly made of iron.
If a giant planet from further out migrates inwards, and eventually falls into the star, this migration will stir up the ingredients. Specifically, it will bring water and gas inwards and eject some of the internal iron. So you end up with earth-type habitable planets, made of a mix of iron, rock, gas and water, in a liquid-water zone.
All large planets eject mass from a system. That is not an issue. In fact, outer gas giants eject more mass. From your paper:
"An outer giant planet ejects approximately one half of the total terrestrial mass in the system, while a hot jupiter can remove up to one third of the total mass."
What matters is the mix of materials left. You will note that the paper I cited earlier suggested that our solar system might have experienced an earlier migrating giant planet, a suggestion which this paper also supports. In fact, migrating gas giants may be the norm, and it may be that habitable planets composed of an iron core with a rocky outside and water on the surface can only form in this way.
The paper you have cited is in agreement with Mandell, Raymond and Sigurdsson (2007) ( http://iopscience.iop.org/0004-637X/660/1/823/70644.text.html ) which says:
"If planetary systems that suffer the migration of a gas giant to small distances can eventually form terrestrial planets similar to those in our own system, and the migration of young giant planets is a common result of interactions with the gaseous disk, then it is appropriate to consider the possibility that our own planetary system could have formed earlier generations of giant planets prior to those in the outer solar system.
It is early days yet, as I have often said, but it looks to me as if the migrating hot jupiter theory provides a good explanation of how inner habitable planets can be formed, and may well be the norm for our kind of system....
Do you try and get things wrong deliberately? The evidence suggests you must do. Of course while just posting in a forum, I forgot there are always some people around who expect a science paper to be provided to support every post.
You state "........hot jupiter, which, I understand, you do not believe. Look at its conclusions:"
To correct you once again, I have never said I do not believe hot jupiters will always prevent terrestrial planets forming or that they will always eject terrestrial planets from forming in the habitable zone. I do believe it is very likely this will be the case but as most of us are prepared to acknowledge, there will always be exceptions to the rule especially in a galaxy with billions of stars.
But. you carry on misrepresenting what people post if that lights your candle.
I have said and will say again, that research of 2500 simulations showed in every case migrating hot jupiters caused terrestrial planets to be ejected from an exo solar system. I've acknowledge I cannot find the link to this but I could trawl through the 'There's no one out there' thread to find it. If I had time and wanted to take every poster to task as you do, I dare say I could find it again.
You provided a paper that suggested otherwise. In response, I posted a link to another paper which stated clearly although you appear to have ignored, that HJ's can and will disrupt the planeeisimal matter as they migrate inwards. The article also stated that if this migration happens in the first million or so years of the exo systems existence, the planetesimal matter has chance to re form and allow terrestrial planets to form after the migration.
The article also states that if the HJ's migrate later than this, the results are very different. Of course at the moment, even the paper you alude to is not supported by all the evidence so far gathered. And this is that where an exo solar system has HJ's the information to date is that terrestrial planets in the habital zone are virtually non existeant. We could concur this is because the HJ have ejected or prevent terrestrial planets from forming.
Oh and just so we are clear, when I mention terrestrial planets, I mean terrestrial sized planets in the habitable zone. Rocky terrestrial planets may form in closer to the parent star even with HJ's but so what? I gather one dataset from Kepler alludes to such a scenario http://www.telegraph.co.uk/science/space/7966992/Three-vast-planets-found-orbiting-distant-star.html.
So I guess you could triumphantly claim that even with an HJ in an exo solar system, we now have evidence that terrestrial planets can still form. Whoopee- do!
Despite this, the premise still holds. That is Kepler's
-
... I forgot there are always some people around who expect a science paper to be provided to support every post. ...I have said and will say again, that research of 2500 simulations showed in every case migrating hot jupiters caused terrestrial planets to be ejected from an exo solar system. I've acknowledge I cannot find the link to this ...
If you are making a scientific claim it is an absolute requirement to provide the research evidence.
"You provided a paper that suggested otherwise. In response, I posted a link to another paper which stated clearly although you appear to have ignored, that HJ's can and will disrupt the planeeisimal matter as they migrate inwards. The article also stated that if this migration happens in the first million or so years of the exo systems existence, the planetesimal matter has chance to re form and allow terrestrial planets to form after the migration.
The article also states that if the HJ's migrate later than this, the results are very different. "
Indeed. The paper goes on to state that creation and migration of HJs is typically rapid, within 1.1 Myr.
"...recent results show that giant planets can form on very short timescales (Boss 1997; Mayer et al 2002; Rice et al 2003). New simulations of the standard core-accretion scenario (Pollack et al 1996) including turbulence (Rice and Armitage 2003) and migration during formation (Alibert et al 2004) have shown that giant planets can form via this mechanism in 1,000,000 years or less....
The timescale for the inward migration of a giant planet depends on the mass of the planet and the mass and viscosity of the gaseous disk, and is typically less than 100,000 years for Saturn and Jupiter-mass planets. Migration begins immediately after, even during, the formation of the giant planet....
So a 'normal' HJ system migrates rapidly, and WILL retain the building blocks of a terrestrial planet within the habitable zone, after they have been carried there by the migrating HJ. If this has happened here, it would explain why we have a rocky AND gaseous planet. The distribution of water and other volatiles in the inner Solar System is still not well understood, and it looks to me as if migrating HJs, rather than being a threat to terrestrial-type planets, could in fact be the creators of them.
Despite this, the premise still holds. That is Kepler's
It is hard to tell what premise you refer to in your final sentence, which is incoherent. Is a part missing? However, given your title of 'Keppler mission adds more weight to our solar system not being the norm', I would suggest that a system showing HJs which have migrated close to their sun is exactly what you would expect to see during the early stages of a system which will have terrestrial type planets in the habitable zone.
-
So I guess you could triumphantly claim that even with an HJ in an exo solar system, we now have evidence that terrestrial planets can still form. Whoopee- do!
In this case: not necessarily!
That terrestrial (sized) planet is in a day-and-a-bit orbit, inside two Saturn-type planets in 19 and 38 day orbits. All going around a star very much like the sun. In our system, Mercury (in an 88-day orbit) has a surface temperature of up to 700K.
So the terrestrial planet there could be no more than the rocky remnant core of a former hot Jupiter.
Andy
-
So the terrestrial planet there could be no more than the rocky remnant core of a former hot Jupiter.
Andy
Indeed. At that range from the sun (around 1.86 million miles?) I would agree that this is the most likely possibility. I suspect that it is being ablated, and experiencing drag from the solar wind, so will probably disappear entirely in a short time.
-
A quick play with Excel suggests the surface temparture there must be around the 2200K mark. Well over the temperature of molten rock. Even titanium would be a puddle.
-
Interesting calculation! I wonder what G is there...
If it's boiling away and losing mass I suspect that will tend to make it fly away from the sun, while the drag from the solar wind will slow it down and make it tend to fall into the sun. That effect might stabilise its orbit for a while, but I would guess that in a 100k years or so it will be completely vaporised.....
-
If you are making a scientific claim it is an absolute requirement to provide the research evidence.
Absolute tosh. This is a general chat forum for subjects to be discussed in a matter of fact way. So most people wouldnt expect or demand scientific papers. You continually spoil perfectly reasonable debate by requiring scientific papers to support a debate or, as is usually your want, to stifle debate.
You just troll threads trying to make your self look important.
Indeed. The paper goes on to state that creation and migration of HJs is typically rapid, within 1.1 Myr.
"...recent results show that giant planets can form on very short timescales (Boss 1997; Mayer et al 2002; Rice et al 2003). New simulations of the standard core-accretion scenario (Pollack et al 1996) including turbulence (Rice and Armitage 2003) and migration during formation (Alibert et al 2004) have shown that giant planets can form via this mechanism in 1,000,000 years or less....
The timescale for the inward migration of a giant planet depends on the mass of the planet and the mass and viscosity of the gaseous disk, and is typically less than 100,000 years for Saturn and Jupiter-mass planets. Migration begins immediately after, even during, the formation of the giant planet....
So a 'normal' HJ system migrates rapidly, and WILL retain the building blocks of a terrestrial planet within the habitable zone, after they have been carried there by the migrating HJ. If this has happened here, it would explain why we have a rocky AND gaseous planet. The distribution of water and other volatiles in the inner Solar System is still not well understood, and it looks to me as if migrating HJs, rather than being a threat to terrestrial-type planets, could in fact be the creators of them.
It is hard to tell what premise you refer to in your final sentence, which is incoherent. Is a part missing? However, given your title of 'Keppler mission adds more weight to our solar system not being the norm', I would suggest that a system showing HJs which have migrated close to their sun is exactly what you would expect to see during the early stages of a system which will have terrestrial type planets in the habitable zone.
And as with all these papers, they are theoretical until definitively proved otherwise. You appear to take them as gospel.
Still, when everyone else acknowledges SETI has been in existence for 50 years yet you state its more like 10 and, wasted what was it, 20 headless pc's crunching useless SETI data for 10+ years, one can begin to understand your frustrations.
Just for once, well, actually for the second time, why dont you let debate flow on an every day level instead of trying to bull yourself up? Dont bother answering that as it was a rhetorical question.
-
Just as an aside, I wonder why it is that Humankind are so hellbent on trying to discover life as we know it on other planets.
For eons we human have looked towards the stars and wondered how it might be if there may actually exist planets abundantly sustained with the same air that we breathe, the same foodstuffs that we eat, etc, etc. Already we are sending unmanned probes into the heavens, and likewise, already we are being told that the possibility of another planet capable if sustaining human life is pretty much a foregone conclusion.
So what is the deal with this ongoing obsession of trying to colonise other planets which doesn't even belong to us? The question is, what would we do if we were indeed to stumble upon such a life-sustaining planet? And how would WE, the human race, how would we feel if we knew that any particular lifeform from some distant galaxy were intent upon doing the very same thing as us? Could we be trusted not to make the same mess of things as we have to planet Earth. Or indeed, could any alien lifeform be trusted not to make a mess of things once they have found their way here?
Most humans don't even greet their next-door neighbours' with a cheery "Good morning". Indeed, most humans don't even have the foggiest idea of how their neighbours look like. So how in watney would we react should we ever be greeted with a form from a far-distant planet? Or how are we to be trusted, giving that most humans are bent on screwing-up what should be a perfectly good planet anyway? Would our first contact with alien life be a bit of a shocker should it turn out that aliens have the same average mentality of an X-Factor contestant?
A very interesting post. Dont worry, I wont demand you provide links to scientific papers though!
I guess a large part of the answer is, we are as a species (although not the only one by any means) that is naturally inquisitive. We want knowledge, we want to explore and yes to a degree, we want to own.
Theories abound that when \ if we ever do find ETI, it would have a profound effect on most of us. Maybe it will, maybe it wont. I know people who say 'so what if ET contacts us. It wont change my life!'
Perhaps not. I think its a sad perspective of people to say since it would be a great discovery. And if we could talk to another species, maybe it might encourage us to talk to one another.
However, all this is looking more and more unlikely since even SETI observers are beginning to ask if the ways they are looking for ETI are flawed (well yes it is but well done for starting to wake up to that simple fact!). Add in the fact that virtually every one of the exo solar systems found to date are not like ours reduces even further to the very slim chance of ETI's being out there. But that's another thread!
-
You continually spoil perfectly reasonable debate by requiring scientific papers to support a debate or, as is usually your want, to stifle debate.
Are you having problems finding any data to support your assertions? You may find the Wiki to be of assistance: http://en.wikipedia.org/wiki/Hot_Jupiter refers...
-
...virtually every one of the exo solar systems found to date are not like ours reduces even further to the very slim chance of ETI's being out there. But that's another thread!
I think your reasoning is incorrect, but your conclusion is right.
All the methods used to discover extrasolar planets introduce a bias towards finding systems that aren't like the solar system. At the moment they can only detect close in, large planets, which is not the model underlying our own solar system.
That's not all bad news, because it does prove that planets are likely to be common - there's 490 extrasolar ones known right now. A few years ago we knew of none, but the fact is that the formation of just about any kind of a star is potentially able to create planetary systems (and dust rings) of a findable type.
Ok - so why don't we discover hot Jupiters around just every star that's looked at, if planet formation is not uncommon? I'd argue that it's precisely because our solar system isn't unique, and many stars might well have systems not unlike ours, that are currently undetectable.
As to "life" I strongly believe it's just chemistry, time and chance; and in those terms our kind of carbon-based life could well start all over the place. The right materials exist throughout our solar system, and we know of liquid water under Europa, in Enceladus, and there's a great chance of liquid brines under Mars, too. Toss in 100 billion stars in the galaxy, and I think we'll ultimately find that living things are ubiquitious. Look at it this way, our universe clearly has the physics, structure and age which make it life-friendly.
Intelligent, communicating life, on the other hand, I think is an extreme rarity - we're the outcome of some stupendously lucky breaks from our single-celled ancestors - and I'd point you to Fermi's Paradox for a likely proof of that rarity.
Andy
-
I think your reasoning is incorrect, but your conclusion is right.
All the methods used to discover extrasolar planets introduce a bias towards finding systems that aren't like the solar system. At the moment they can only detect close in, large planets, which is not the model underlying our own solar system.
That's not all bad news, because it does prove that planets are likely to be common - there's 490 extrasolar ones known right now. A few years ago we knew of none, but the fact is that the formation of just about any kind of a star is potentially able to create planetary systems (and dust rings) of a findable type.
Ok - so why don't we discover hot Jupiters around just every star that's looked at, if planet formation is not uncommon? I'd argue that it's precisely because our solar system isn't unique, and many stars might well have systems not unlike ours, that are currently undetectable.
As to "life" I strongly believe it's just chemistry, time and chance; and in those terms our kind of carbon-based life could well start all over the place. The right materials exist throughout our solar system, and we know of liquid water under Europa, in Enceladus, and there's a great chance of liquid brines under Mars, too. Toss in 100 billion stars in the galaxy, and I think we'll ultimately find that living things are ubiquitious. Look at it this way, our universe clearly has the physics, structure and age which make it life-friendly.
Intelligent, communicating life, on the other hand, I think is an extreme rarity - we're the outcome of some stupendously lucky breaks from our single-celled ancestors - and I'd point you to Fermi's Paradox for a likely proof of that rarity.
Andy
Clearly, our technology prior to kepler could, in the main, only detect planets close in to their parent star. Kepler has the ability to detect exo solar systems that match our own and time will tell if results from kepler start to swing the bias toward solar systems like ours. Im still not convinced this will be the case though. That which is easily found tend to be the most common. And planetary systems with HJ's close in are currently the most common. Even now, early in the mission, kepler is returning results of more systems with HJ's although it appears to have spotted smaller terrestrial sized planets even closer to the parent stars.
Therefore, in the time for kepler to positively spot planetary systems like ours, if they do exist, it will have undoubtedly have uncovered many more that aren't leading more weight to the fact that ours is tending towards uniqueness.
I dont disagree with your comments about the chances of intelligent life. I think it will be exceedingly rare in our galaxy. Fermi was correct, where are they all? The rare earth theory proves an insight to this but as I said before, that's another thread.
-
That which is easily found tend to be the most common.
Not at all. If I wanted to do a survey of the UK's population, to determine general statistics of age and gender, and my search parameters only let me look in model boat clubs (for example!), I'd have biased results. As I mentioned earlier, Kepler's results currently have a bias similar to the previous methods of planet detection. Time (i.e. the chance to see longer-period transits) will tell, of course - and the good news is that Kepler's got years of life left in it.
Andy
-
Not at all. If I wanted to do a survey of the UK's population, to determine general statistics of age and gender, and my search parameters only let me look in model boat clubs (for example!), I'd have biased results. As I mentioned earlier, Kepler's results currently have a bias similar to the previous methods of planet detection. Time (i.e. the chance to see longer-period transits) will tell, of course - and the good news is that Kepler's got years of life left in it.
Andy
Then you clearly dont subscribe to okam's razor.
I'd disagree regarding your observation of model boat clubs. Many clubs have members of all ages. And I dont think anyone would claim they are all male preserves so your survey would show male, female young and old. In other words your survey would show a cross section of the population, young, old, male and female.
In my experience, that applies to every club I've been in ie angling, motoring, numerous RC clubs etc, etc but obviously I cannt speak for others and the clubs they have been in.
Kepler's got a little less than 4 years mission time left though. So, it has to start finding many more exo solar systems like ours towards the end of its mission time due to the methodology and its mission requirements ie three transits to confirm the orbital period of planets that would confirm a planet as being in the habital zone of its parent star similar to ours.
Since systems with HJ's will likely affect the number of terrestrial sized planets in the habitable zone and, vastly reduced transit times planets in these systems have, kepler will find many more exo systems unlike our own.
-
... Even now, early in the mission, kepler is returning results of more systems with HJ's although it appears to have spotted smaller terrestrial sized planets even closer to the parent stars.
Therefore, in the time for kepler to positively spot planetary systems like ours, if they do exist, it will have undoubtedly have uncovered many more that aren't leading more weight to the fact that ours is tending towards uniqueness.
This suggests a fundamental misunderstanding about the process which the Keppler probe is using to detect planets.
Keppler is looking for the slight dip in a star's brightness when a planet passes across it. This means that, if a planet has an orbital period of 10 days Keppler can detect it in a minimum of 20 days - the time for it to do two orbits and provide a matched pair of dips. Ideally, you might like 3 dips in 30 days. If a planet has an orbital period of 365 days Keppler might detect it in 720 days, or 1095 if 3 dips is preferred. But during this time Keppler will not be detecting more and more 10 day planets. They will have been detected already.
So we expect Keppler to detect lots of short-period planets to start off, and for these short-period detections to slow down as time progresses, and more long-period planets start to be found. I suppose that Keppler could only be pointed at a particular system for, say, 40 days - in which case it could only see planets with a period of 20 days or less. But that would be an obviously biased set of data....
-
I'd disagree regarding your observation of model boat clubs. Many clubs have members of all ages. And I dont think anyone would claim they are all male preserves so your survey would show male, female young and old. In other words your survey would show a cross section of the population, young, old, male and female.
I'm sure my survey would.
Meanwhile, the Office of National Statistics says "In mid-2009 the average age of the population was 39.5 years". And we know that there are more women in the UK than men, so the commonest gender is female.
While there probably are both sexes and all ages in most model boat clubs, I strongly suspect that the commonest gender if you were to total all of them would be male, and the average age probably greater than 39.5. -> observational bias at work -> the survey is flawed.
Kepler's got a little less than 4 years mission time left though. So, it has to start finding many more exo solar systems like ours towards the end of its mission time due to the methodology and its mission requirements ie three transits to confirm the orbital period of planets that would confirm a planet as being in the habital zone of its parent star similar to ours.
Because we're talking science and statistics, to be pedantic, Kepler doesn't "have" to do anything.
But I totally agree that its results can't confirm any planets that lie in orbits whose duration is longer than the current observational period. Since these can't pop-out of the data until later, we therefore can't say at the moment that HJs are commonest (because of the observational bias), or (impossible to prove) that the Solar System is not the norm.
Finally - and kudos to the Kepler team, who understand their methodology - they may well already have possible single transits of habitable zone planets, but they're only releasing data when they can confirm orbits. (And full data will be released to us all, once they've been peer-reviewed and have published their results.)
Andy
-
But I totally agree that its results can't confirm any planets that lie in orbits whose duration is longer than the current observational period. Since these can't pop-out of the data until later, we therefore can't say at the moment that HJs are commonest (because of the observational bias), or (impossible to prove) that the Solar System is not the norm.
Dreadnought72 is quite correct. It may be true that HJs are very common and terrestrial-type planets are very rare, but the Keppler data does not support this at the moment. If there are few or no planets detected in habitable zones after, say, three years, then the Keppler data will support this assertion. But not before....
-
Well, potentially new evidence to show our solar system tends towards uniqueness http://www.newscientist.com/article/dn19429-laws-of-physics-may-change-across-the-universe.html if our part of the galaxy is 'just right' for our existence.
If that's the case, then you could possibly forget about finding lots of exo solar systems that resemble ours.
Course no one is suggesting Kepler's data suggests all undiscovered exo solar systems will be totally unlike our own. The data currently returned just adds weight to the evidence we have that our solar system is not like anything we have found so far ie ours is tending towards uniqueness.
-
This suggests a fundamental misunderstanding about the process which the Keppler probe is using to detect planets.
Keppler is looking for the slight dip in a star's brightness when a planet passes across it. This means that, if a planet has an orbital period of 10 days Keppler can detect it in a minimum of 20 days - the time for it to do two orbits and provide a matched pair of dips. Ideally, you might like 3 dips in 30 days. If a planet has an orbital period of 365 days Keppler might detect it in 720 days, or 1095 if 3 dips is preferred. But during this time Keppler will not be detecting more and more 10 day planets. They will have been detected already.
So we expect Keppler to detect lots of short-period planets to start off, and for these short-period detections to slow down as time progresses, and more long-period planets start to be found. I suppose that Keppler could only be pointed at a particular system for, say, 40 days - in which case it could only see planets with a period of 20 days or less. But that would be an obviously biased set of data....
Im fully aware of kepler's MO thanks.
Clearly, kepler will find many short period orbital objects, both HJ's and terrestrial sized planets early in the mission since 3 transits can be observed in a shorter period of time. But, the big question is, come 3 and a bit years, how many exo solar systems will it have found like ours to how many more systems with HJ's and therefore unlike ours, will it have found?
Im willing to bet kepler will find an inordinate amount of systems with hj's and very, very few if any, like ours. Now wouldnt that be fun?
Oh and by the way, NASA call it the Kepler mission not keppler
http://kepler.nasa.gov/
-
Well, potentially new evidence to show our solar system tends towards uniqueness http://www.newscientist.com/article/dn19429-laws-of-physics-may-change-across-the-universe.html if our part of the galaxy is 'just right' for our existence.
Read deeper!
If alpha differed by 4% then, yes, they'd be big problems.
Thing is, the latest figures for a change in alpha suggest Δα̇/α = (−1.6 ± 2.3) × 10−17 per year: around about 20000ths of a percent (and potentially not at all, when you look at the error bars) since the Big Bang = makes no difference whatsoever to planet formation.
Andy
-
But, the big question is, come 3 and a bit years, how many exo solar systems will it have found like ours to how many more systems with HJ's and therefore unlike ours, will it have found?
You seem to make a lot of early assumptions which get invalidated by later events, and then ignore those events which disprove you. Now that it is understood that a system with HJs IS compatible with terrestrial planets, and that HJs seem to be a common precursor to solar systems, researchers are starting to consider looking for the remains of an HJ in our own system, on the assumption that we ARE like the systems we are seeing.
You also do not seem to have considered the ratio of HJs detected to systems with normal gas giants, detected by other projects. If detecting an HJ indicates that a system is 'unlike ours', I presume that you would agree that detecting a gas giant in a 'normal position' would suggest that a system is 'like ours'?
All the current data on detected planets can be found in the ExtraSolar Planets Encyclopedia - http://exoplanet.eu/catalog-all.php
If you put this on a spreadsheet you will see that there's a cluster in the 1-10 day range, representing the 'hot Jupiters', and another, larger, cluster of gas giants with orbital periods of about 1-10 years, representing 'standard gas giants'. We have around 150 HJs found, and 200 'normal Jupiters'.
So, even though we are preferentially detecting low-period planets at the moment, we still know of more long-period planets. Estimates of the numbers of earth-like planets in the galaxy are now commonly in the billions...
Im willing to bet kepler will find an inordinate amount of systems with hj's and very, very few if any, like ours. Now wouldnt that be fun?
As I said earlier, you DO tend to jump the gun a lot, don't you? You're lucky I'm not a betting man, but you should find no shortage of people to take you up on that one. A couple of months ago this happened:
http://news.discovery.com/space/kepler-scientist-galaxy-is-rich-in-earth-like-planets.html
So you can see that current discoveries seem to suggest that earth-type planets ARE common in the galaxy and that our system seems to be perfectly normal. Arguing that this is not true seems to be wilfully ignoring the latest findings.
We will not have long to wait for the first data release in Feb 2011. And when we get SIM Lite up there, I expect this will enable us to disprove the 'rare-earth' hypothesis completely...
-
Just to be clear, the "like Earth" shown here (a PowerPoint slide grabbed from the Kepler scientist's lecture):
(http://blogs.discovery.com/.a/6a00d8341bf67c53ef0133f291cd81970b-pi)
Is for size, as it states, not for the planet's distance from the primary star.
Andy
-
Just to be clear, the "like Earth" shown here (a PowerPoint slide grabbed from the Kepler scientist's lecture):
(http://blogs.discovery.com/.a/6a00d8341bf67c53ef0133f291cd81970b-pi)
Is for size, as it states, not for the planet's distance from the primary star.
Andy
A very reasonable point, Dreadnought72. Of course, we are detecting the close-in planets first, and so most of these will be Mercury-type (or nearer!) rather than Earth-type. We must endure the few years wait to get the planets of 365 days period. But I think the key point - that HJs do not preclude smaller planets - is made pretty well. All we need to do now is wait for the 'Goldilocks instance'...
-
New simulations show Jupiter sized planets can seriously affect other planets location in a solar system. Simulations show Uranus likely to have been shunted further out into the solar system by Jupiter and Saturn, similar to how like HJ's would with close in terrestrial sized planets.
http://www.newscientist.com/article/mg20727785.300-did-jupiter-and-saturn-play-pinball-with-uranus.html
-
Just to be clear, the "like Earth" shown here (a PowerPoint slide grabbed from the Kepler scientist's lecture):
(http://blogs.discovery.com/.a/6a00d8341bf67c53ef0133f291cd81970b-pi)
Is for size, as it states, not for the planet's distance from the primary star.
Andy
Correct. Too many people think earth like mean like the earth ie similar size and in the same position.
I dont recall anyone saying HJ's prevent smaller terrestrial sized planets forming, totally. The information is suggests this is dependant on when the HJ migrated in relation to a solar system forming.
However, I still think people are going to be majorly disappointed when Kepler's mission is complete and the information resulting shows our system does indeed tend towards uniqueness.
I've no doubt the overwhelming evidence from Kepler will show lots of terrestrial sized planets but they will be close in to the parent star, unlike our planet.
-
However, I still think people are going to be majorly disappointed when Kepler's mission is complete and the information resulting shows our system does indeed tend towards uniqueness.
I've no doubt the overwhelming evidence from Kepler will show lots of terrestrial sized planets but they will be close in to the parent star, unlike our planet.
Think that, by all means. But don't claim that that the mission evidence suggests this at the moment. Here is the NASA press release from March of this year:
"...The first planets to roll out on the Kepler "assembly line" are expected to be the portly "hot Jupiters" -- gas giants that circle close and fast around their stars. NASA's Hubble and Spitzer space telescopes will be able to follow up with these planets and learn more about their atmospheres. Neptune-size planets will most likely be found next, followed by rocky ones as small as Earth. The true Earth analogs -- Earth-sized planets orbiting stars like our sun at distances where surface water, and possibly life, could exist -- would take at least three years to discover and confirm..."
http://science.nasa.gov/science-news/science-at-nasa/2009/06mar_keplerlaunch/
So far these predictions have been accurate.
-
Just as an aside, I wonder why it is that Humankind are so hellbent on trying to discover life as we know it on other planets.
For eons we human have looked towards the stars and wondered how it might be if there may actually exist planets abundantly sustained with the same air that we breathe, the same foodstuffs that we eat, etc, etc. Already we are sending unmanned probes into the heavens, and likewise, already we are being told that the possibility of another planet capable if sustaining human life is pretty much a foregone conclusion.
So what is the deal with this ongoing obsession of trying to colonise other planets which doesn't even belong to us? The question is, what would we do if we were indeed to stumble upon such a life-sustaining planet? And how would WE, the human race, how would we feel if we knew that any particular lifeform from some distant galaxy were intent upon doing the very same thing as us? Could we be trusted not to make the same mess of things as we have to planet Earth. Or indeed, could any alien lifeform be trusted not to make a mess of things once they have found their way here?
Most humans don't even greet their next-door neighbours' with a cheery "Good morning". Indeed, most humans don't even have the foggiest idea of how their neighbours look like. So how in watney would we react should we ever be greeted with a form from a far-distant planet? Or how are we to be trusted, giving that most humans are bent on screwing-up what should be a perfectly good planet anyway? Would our first contact with alien life be a bit of a shocker should it turn out that aliens have the same average mentality of an X-Factor contestant?
I am of the opinion, that the above is the most sensible answer ,I have read for a long time,well done PMK,..my personal opinion of it all, is that its all pure conjecture,..a load of "what ifs or might be,s...but If an extra-terrestrial does happen to get himself lost,and and on earth,I,have no doubt,he,or them,will be locked away somewhere,before they see the light of day,..because if their not,..then that Ack Ack Gunner thats here on a visit,..well.he,ll have some explaining to do,..
Wullie
-
I find all these discussions/arguments fascinating, thank you.
I also agree that we seem determined to find some life form very much like us. Why?
I try to imagine that there may be some form of life but what it will be like eludes my thought processes. Why should it be carbon or hydrogen based? But I guess it then raises the question of what do you mean by "life form"?
You also raise the issue of our and their "intentions". I guess that depends, in the first instance, on our ability to communicate.
Another fascinating thought I often have is, would they have a God or Gods? If you are a Christian surely you must ask do they know Lord and is He their Saviour also?
Encountering the unknown triggers a natural human response of fear/suspicion which is quickly followed by aggression on our part. It is a natural and understandable safety mechanism, probably most difficult to control. For example not only do we not speak to our neighbours, before we get to know them we ostracise them if they are foreign or coloured !
Any Earth world leader who walked up to an alien and said "Welcome" would probably be killed.....not by the alien but by his or her electorate !
Roger in France.
-
I belive in Aliens
%% %% %% %% %% %% %% %% %% %% %% %% %% %% %% %% {-) {-) {-) {-) {-) {-) {-) {-) {-)
(http://a1star.com/images/area51.gif) (http://a1star.com/images/alien-abduction-spaceship.gif)
-
Just as an aside, I wonder why it is that Humankind are so hellbent on trying to discover life as we know it on other planets....
They might have a decent pond there....
-
I belive in Aliens
%% %% %% %% %% %% %% %% %% %% %% %% %% %% %% %% {-) {-) {-) {-) {-) {-) {-) {-) {-)
(http://a1star.com/images/area51.gif) (http://a1star.com/images/alien-abduction-spaceship.gif)
I have walked on Blackpool prom. So do I.
-
...Another fascinating thought I often have is, would they have a God or Gods? If you are a Christian surely you must ask do they know Lord and is He their Saviour also?...
You might be interested in the James Blish book 'A Case of Conscience' - http://en.wikipedia.org/wiki/A_Case_of_Conscience#Reference-idBlish_1999 refers. If you wish to research the book a bit you will find mention of the actual Catholic Church guidelines for dealing with extraterrestrials. Blish, one of my favourite writers, was a stickler for accuracy....
...Any Earth world leader who walked up to an alien and said "Welcome" would probably be killed.....not by the alien but by his or her electorate !..
I suggest that if we haven't risen in revolt and killed our political classes for what they have already done to us, we are unlikely to do so when they sell the Earth to alien developers for turning into a theme park...
-
I read in the paper today that Boffins at St,Andrews Uni,believe that solar dust clouds,could contain rubies and emeralds?????what planet are they on, {-)
furthermore,in the same paper,..their saying that in 3 years time,we could suffer the consequences of a massive Solar Flare that may or may not be ejected from the currant bun,If it is ejected then we could have cataclysmic catastrophies,all over the planet,similar they say, to what happened in the film 2012,...I can see the Sandwich Boarders, of the 1950,s,coming out again,..proclaiming..."The World is Nigh"beware 2013,sfunny how they always make sure these predictions almost always land on a 13 {-)
Wullie
-
I read in the paper today that Boffins at St,Andrews Uni,believe that solar dust clouds,could contain rubies and emeralds??...
I believe that about 6 ten-billionths (0.0000000006) of the mass of the sun consists of atoms of gold. That would be about 1/500 of the mass of the Earth? It would make a decent sized lump. Now all we have to do is collect it....
-
I believe that about 6 ten-billionths (0.0000000006) of the mass of the sun consists of atoms of gold. That would be about 1/500 of the mass of the Earth? It would make a decent sized lump. Now all we have to do is collect it....
We'll have to go at night, when its cooler.
-
We'll have to go at night, when its cooler.
Aha, Malcolm, I think I can see a problem with that plan.
You're never going to make it all the way there and back in one night...... %% %%
-
First habitable exo Earth to be found http://www.newscientist.com/article/dn19474-is-there-a-moores-law-for-science.html sometime in May 2011 if this is to be believed.
Can the rate of past discoveries be used to predict future ones? We may soon find out. Two researchers have used the pace of past exoplanet finds to predict that the first habitable Earth-like planet could turn up in May 2011.
-
Think that, by all means. But don't claim that that the mission evidence suggests this at the moment. Here is the NASA press release from March of this year:
"...The first planets to roll out on the Kepler "assembly line" are expected to be the portly "hot Jupiters" -- gas giants that circle close and fast around their stars. NASA's Hubble and Spitzer space telescopes will be able to follow up with these planets and learn more about their atmospheres. Neptune-size planets will most likely be found next, followed by rocky ones as small as Earth. The true Earth analogs -- Earth-sized planets orbiting stars like our sun at distances where surface water, and possibly life, could exist -- would take at least three years to discover and confirm..."
http://science.nasa.gov/science-news/science-at-nasa/2009/06mar_keplerlaunch/
So far these predictions have been accurate.
I'll voice my thoughts whenever I want thanks and thank you to stop twisting other people's comments and saying 'dont claim' this or that.
I think everyone was aware, given the MO for the kepler mission, that the first results would be of HJ's or smaller planets closer to the star having short orbital periods! As for saying 'so far these predictions have been accurate' I'd go so far as to say they are virtually stating the bleedin obvious.
-
I find all these discussions/arguments fascinating, thank you.
I also agree that we seem determined to find some life form very much like us. Why?
I try to imagine that there may be some form of life but what it will be like eludes my thought processes. Why should it be carbon or hydrogen based? But I guess it then raises the question of what do you mean by "life form"?
You also raise the issue of our and their "intentions". I guess that depends, in the first instance, on our ability to communicate.
Another fascinating thought I often have is, would they have a God or Gods? If you are a Christian surely you must ask do they know Lord and is He their Saviour also?
Encountering the unknown triggers a natural human response of fear/suspicion which is quickly followed by aggression on our part. It is a natural and understandable safety mechanism, probably most difficult to control. For example not only do we not speak to our neighbours, before we get to know them we ostracise them if they are foreign or coloured !
Any Earth world leader who walked up to an alien and said "Welcome" would probably be killed.....not by the alien but by his or her electorate !
Roger in France.
Im not sure that people who consider the possibility of alien life are determined to find it like ourselves. I think we are on the cusp of discovering alien life on Mars or some of the moons of Jupiter etc. Obviously I dont have a scientific paper or thesis to satisfy a certain poster on here though! I think is only the general population, fed on a diet of hollywood films etc, who see alien life as being more or less humanoid and 'being like us.'
I think the reason why its a popular view life would be carbon based rather than any other element is because carbon molecules combine with others very well. That's not to say that alien life definitely wont be based on any other element though. (Again, I dont have any scientific papers to satisfy a certain poster.)
I've said in another thread I think we are probably the oldest most technologically advance race in our galaxy right now (again, no science paper Im afraid!) so think the chances of there being other intelligent life out there to communicate with us as being remote.
Having said that, its a statistical probability that if there are many advanced alien races, there will be as many benevolent as malevolent ones.
-
...I think we are on the cusp of discovering alien life on Mars or some of the moons of Jupiter etc....
I think the reason why its a popular view life would be carbon based rather than any other element is because carbon molecules combine with others very well. That's not to say that alien life definitely wont be based on any other element though. (Again, I don't have any scientific papers to satisfy a certain poster.)
You hardly need any references for these assertions, which are completely in line with current thinking. If you want any, there are many available - nowadays exobiology conferences are quite common. Here are a few you might be interested in...
http://astrobiology.nasa.gov/exobiology/?pg=2
http://www.spacedaily.com/news/life-00p1.html
http://books.nap.edu/openbook.php?record_id=11919
http://www.pnas.org/content/98/3/805.full.pdf
http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry
...
I've said in another thread I think we are probably the oldest most technologically advance race in our galaxy right now (again, no science paper Im afraid!) so think the chances of there being other intelligent life out there to communicate with us as being remote.
Current understanding of the development of organic life suggests that it might be common wherever the conditions allow it to exist. Our own planet, developed life just about as soon as it cooled down - sufficiently rapidly for there to be a sizeable body of belief that life was 'seeded' from space rather than developed terrestrially.
There are two oddities in the history of 'Life on Earth' - the rapidity of its initial development, and the peculiar delay in the development of 'higher' intelligence. Most of the more complex life forms which have inhabited this planet seem to have had a fair degree of intelligence - it is needed for both predator and herd lifestyles. What is surprising is that the kind of abstract higher intelligence developed recently by a few species of mammals (notably cetaceans and primates) seems to have taken a very long time to occur. You would think, if it had survival value, that the fish or amphibians would have developed it a lot earlier. They have been going for 500m years and 360m years respectively - mammals have only been going for 200m, dolphins and apes are about 40m years old and we have only been going for perhaps 2m years. Why is this?
This suggest to me that, if you want to consider the prevalence of higher intelligence in the universe, paeleobiology is a more important subject than astronomy. Of course, there are some speculations that the giant reptiles of 300m years ago DID develop intelligence, but it turned out not to have survival value, and so died out quite fast...
-
Big brains cost a lot.
Ours weigh about 2% of the total body mass (considerably less for people in government!) but use a fifth of the body's energy. From an evolutionary point-of-view that's an incredibly expensive investment, and not least when you add in the risks - giving birth to a human is dangerously hard work, and you end up with an infant incapable of much for a year or so.
You can get by on tiny brains - an ant has around 10,000 neurons, a bee about 800,000. Plenty for the things they do, for predation, for social grouping, etc.
Developing the millions of neurons used by mammals, and the tens-of-billions used by us strikes me as an aberration more than the norm. Think of it as an mammalian arms-race that has spun out of control, if you like. We've left the almost-steady-state of unicellular life, and the slow progression of big-enough-brained multicellular life, and only very recently accelerated to a position where (with our mighty brains) we can wipe out everything. Or - perhaps in a century or two - upload human existances into non-biological lifeforms.
Andy
-
Big brains cost a lot.
Ours weigh about 2% of the total body mass (considerably less for people in government!)
Presumably that's because sedentary jobs make you fatter, rather than make your brain smaller... :} :}
You can get by on tiny brains - an ant has around 10,000 neurons, a bee about 800,000. Plenty for the things they do, for predation, for social grouping, etc.
.
Yes - a roundworm can get by on 302! But I think there is a bit more difference between the insects and higher orders. A single ant does not really predate, and I carefully used the words 'herd lifestyles' in an effort to distinguish between the social insects and animals like cows. Anthills aren't herds, and most insects seem to have very simple pre-wired responses...
I think your figure for humans is a total neuron count? I have seen neuron counts for humans of approx 11bn in the cerebral cortex. For comparison, chimps weigh in at about 6.2bn, dolphins at 5.8bn, cats at about 0.3bn and dogs at 0.15bn, which certainly makes humans superior, but not fantastically so. You are correct, of course, that we have specialised in brain power to the detriment of other bodily aspects, and this may prove to be counter-productive in the long (or medium!) term.
But it still leaves the question of why this neural arms-race did not occur in fish or reptiles, and why the world had to wait for 500m years of complex animal evolution before one group developed 'high intelligence' in less than 10m years...
-
Evolution only happens where it is needed.
If you live in a benign climate, with potable water laid on on a regular basis, abundant food there for the taking and somewhere comfy to rest at night, what incentive for change is there? Change becomes needed when conditions are marginal, and some new aspect of lifestyle that gives an advantage, whether its the use of a stick to get an advantageous supply of termites or the use of a shady leaf to see the fishes better will see some individuals have a better chance of survival. Those who exhibit traits for better survival will have more descendants than those who don't, and these traits will tend to be passed on. Not only the trick itself, but the ability to envision further new tricks.
As humans, we tend to be better at gathering new tricks than most other creatures that we share the planet with. Whether the tricks that we have learned are ultimately advantageous or a blind alley remains to be seen.
Having lots of neurons only really counts if they get used, but in the case of the apes from a few million years ago, it might have been a change in conditions that forced a change of diet that in turn caused some individuals to start growing bigger brains. And it could have been a freak mutation triggered by a stray cosmic ray that laid the seed for the exponential rate of change. Remember that exponential rates start long and slow, we think we are on the steep bit at the moment, but we could be fooling ourselves. Being able to think does that for you, as well.
Just a random thought - when did opposable thumbs get invented?
-
But it still leaves the question of why this neural arms-race did not occur in fish or reptiles, and why the world had to wait for 500m years of complex animal evolution before one group developed 'high intelligence' in less than 10m years...
Fish, reptiles and birds: I suspect the filter there is possibly egg size.
The biggest dinosaur eggs are not much bigger than ostrich eggs. Much bigger and they'd be unbreakable to the "inmate" - and for air-exchange to the developing embryo, that old surface-area/volume ratio works against you as the size increases. A limit on egg size may well force a limit on brain size - and therefore you'd require mammalian/live-born young to expand evolution in the "big-brained" direction.
To answer Malcolm's question - opposable thumbs are great for hanging onto things. No surprise our tree-climbing ancestors had them around fifty million years ago! I have read reports which suggest our ancestor's ability to squat helped free up the role of our fore limbs into more manipulative and dextrous directions, and that this helped promote brain expansion. Though - and no doubt David Attenborough would agree - any element of the body that falls well outside the "norm" (tails of birds-of-paradise, songs of songbirds, brains of humans) has been driven by sexual selection. %)
Andy
-
Fish, reptiles and birds: I suspect the filter there is possibly egg size.
Umm....no, not birds. I was talking about life forms before the mammals, and birds are distinctly after mammals. Though you might also think of them as reptile variants...
But you make a good point about birth size - animals with intelligence do all seem to have large young. Which turns the question of 'Where might we find intelligence?' into ''Where might we find big babies?'...
-
First habitable exo Earth to be found http://www.newscientist.com/article/dn19474-is-there-a-moores-law-for-science.html sometime in May 2011 if this is to be believed.
Can the rate of past discoveries be used to predict future ones? We may soon find out. Two researchers have used the pace of past exoplanet finds to predict that the first habitable Earth-like planet could turn up in May 2011.
Actually, the first 'habitable exo Earth' to be found according to this definition has just been announced (yesterday). It is Gliese 581g, around 20 ly away. http://arxiv.org/abs/1009.5733 refers.
From the Abstract: "..If the local stellar neighborhood is a representative sample of the galaxy as a whole, our Milky Way could be teeming with potentially habitable planets..."
It is beginning to look as if systems with Earth-like planets are quite normal ....
-
Actually, the first 'habitable exo Earth' to be found according to this definition has just been announced (yesterday). It is Gliese 581g, around 20 ly away. http://arxiv.org/abs/1009.5733 refers.
From the Abstract: "..If the local stellar neighborhood is a representative sample of the galaxy as a whole, our Milky Way could be teeming with potentially habitable planets..."
It is beginning to look as if systems with Earth-like planets are quite normal ....
You think? Hardly but you've given me the best laugh I've had all week with this post.
Its a tidally locked planet orbiting a red dwarf 'star.' With one side tidally locked the planet tidally locked, one side will get all the 'sun light' while the other side will be totally in darkness and freezing.
So on a statistic analysis of this one exo planet, you are saying earth like planets are beginning to look quite normal? Now I know you're just trolling.
Since when has the earth been tidally locked and orbiting a red 'dwarf'?
You'll be telling us all next, like Professor Vogt, that you're '100 % certain there's life on the planet' too!
-
Evolution only happens where it is needed.
If you live in a benign climate, with potable water laid on on a regular basis, abundant food there for the taking and somewhere comfy to rest at night, what incentive for change is there? Change becomes needed when conditions are marginal, and some new aspect of lifestyle that gives an advantage, whether its the use of a stick to get an advantageous supply of termites or the use of a shady leaf to see the fishes better will see some individuals have a better chance of survival. Those who exhibit traits for better survival will have more descendants than those who don't, and these traits will tend to be passed on. Not only the trick itself, but the ability to envision further new tricks.
As humans, we tend to be better at gathering new tricks than most other creatures that we share the planet with. Whether the tricks that we have learned are ultimately advantageous or a blind alley remains to be seen.
Having lots of neurons only really counts if they get used, but in the case of the apes from a few million years ago, it might have been a change in conditions that forced a change of diet that in turn caused some individuals to start growing bigger brains. And it could have been a freak mutation triggered by a stray cosmic ray that laid the seed for the exponential rate of change. Remember that exponential rates start long and slow, we think we are on the steep bit at the moment, but we could be fooling ourselves. Being able to think does that for you, as well.
Just a random thought - when did opposable thumbs get invented?
Hmmm. Not certain I agree with that Malcolm. Evolution can happen through simple mutation. Now you may argue mutation only happens when needed but simple exposure to radiation can trigger mutation which may result in a change. But that doesnt mean the change happened because it was needed.
The reason bird and or fish didnt evolve nuclear weapons (!?) is mainly due to size but, a whales brain is (I think) the largest of any creature currently alive today. I dont see them building nuclear bombs though. maybe its because they are more peace loving or the fact its very difficult to make a flame underwater. Not that that is impossible mind. But without flame, you're going to find it very difficult in smelting metals etc.
Professor Vogt has today said he's 100% sure there's life on the new planet. Still, seeing as he's also using this new planet to claim there will be billions of earth like planets out there in the goldilocks zone, I think we could take both of his claims with a pinch of salt.
-
Its a tidally locked planet orbiting a red dwarf 'star.' With one side tidally locked the planet tidally locked, one side will get all the 'sun light' while the other side will be totally in darkness and freezing.
Life would find this similar to our rotating planet where it's hot on the equator while the poles are freezing.
So on a statistic analysis of this one exo planet, you are saying earth like planets are beginning to look quite normal? Now I know you're just trolling.
Since when has the earth been tidally locked and orbiting a red 'dwarf'?
Let us consider the progress of your arguments so far. You started by telling us that Hot Jupiters in a system meant that no small inner planet could exist ("..smaller terrestrial sized planets, if they existed in the system, would be ejected from that solar system..)
When you were shown to be wrong on that, you conceded that a few rocky earth-sized planets might remain, but that
"..terrestrial planets in the habital zone are virtually non existeant.."
and you suggested that since lots of Hot Jupiters were being found they must be very common - ignoring the fact that HJs are much easier to find. The gist of your argument became that 'habitable planets' (small, rocky and in the Goldilocks zone) must be very rare since they have not been discovered at the same rate as HJs (even though we know they are going to be hard to find).
Now we have the first 'habitable planet' to be discovered. Earlier than we expected. I presume you agree that it IS a terrestrial-type planet in the habitable zone? I have been unable to find any support anywhere for your novel view that, because it's probably tidally locked around a red dwarf it doesn't count. Stephen Vogt, one of the leaders of the Lick-Carnegie Exoplanet Survey search team is quoted thus:
"Our findings offer a very compelling case for a potentially habitable planet ... The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."
His 'statistical analysis' refers to the time spent looking and the results found. He seems to agree with your earlier comment: "That which is easy to find tends to be the most common.."? If you still hold that view it must be getting hard to support your contention that habitable planets are vanishingly rare...
-
Hmmm. Not certain I agree with that Malcolm. Evolution can happen through simple mutation. Now you may argue mutation only happens when needed but simple exposure to radiation can trigger mutation which may result in a change. But that doesnt mean the change happened because it was needed.
If there is an unexploited niche, life, if available, will evolve to fill it. It could be through stray radiation modifying DNA, it could be dumb luck. In a reasonably stable system, change is rarely needed, but can happen anyway. The basic design of sharks has remained pretty constant for many millions of years, but there are variations.
Life would find this similar to our rotating planet where it's hot on the equator while the poles are freezing.
The presence of a narrow strip that is neither hot enough to melt metal nor so cold that even a Geordie would put a coat on, with neither night nor day nor seasons, would probably not be good for development. There may be life there, but to quote Spock, "...not as we know it". It would probably be much like Venus - an acid atmosphere and not tectonic movement.
We have the benefit of a huge satellite which acts as a stabiliser, keeping our tilt fairly constant and giving us seasons. It also provides tides, which are the marginal conditions needed for setting up the original evolution mechanism. It also probably helps keep the core temperature high enough so that our water doesn't just drain away and stay there.
We have had several happenings that have shaped life on this planet - the original thud when we gained the moon, then about 259 million years ago when "something" happened to wipe out most of what had evolved, then 65 million years ago when the slate was given a good wipe again. Just how much of this was essential to our development is really impossible to say, but is we needed all of it, any other planet might well need something similar, and on a similar timescale to arrive at a compatible point.
Being the right sort of size and at the right distance is not the entire story. There might be millions of such out there, but if it also, for each one, needs a few several million to one chances for life to establish and evolve, there really aren't going to be many.
"Our findings offer a very compelling case for a potentially habitable planet ... The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."
I would read this as a coded way of saying "Keep the funding coming, I like having an indoors job with no heavy lifting". Is that cynical or sceptical?
-
The presence of a narrow strip that is neither hot enough to melt metal nor so cold that even a Geordie would put a coat on, with neither night nor day nor seasons, would probably not be good for development.
Three points:
Tidal lock on bodies in elliptical orbits (which this planet surely has) always results in a process of libration - a gentle wobble around the lock point. It's the libration of the Moon, for example, that allows us on Earth to see 59% of the lunar surface, over time. For this planet, that "narrow strip" of comfortable living could, therefore, be quite extensive. The presence of an atmosphere - just about a "given", seeing the planet's mass and gravity are high - will somewhat negate the extremes of cold and hot, as heat will be transferred from the hot sun-facing "pole" to the cold "pole".
As to tectonic conditions (and the suggestion of a Venusian-style atmosphere) we have no idea. The star is old, much older than the Sun, so radioactives in the planets will provide less heat than they used to. The stars metallicity is about half that of the Sun's, so again it's likely that these planets are more heavy-metal deficient than our own. That said, this new planet is big - three times the mass of the Earth and perhaps 50% bigger - so it will lose residual heat more slowly than the Earth, and this might mean a "normal" tectonic process is still on-going. We can't say either way that it is or isn't.
Finally: with one data point (the Earth) we really have little idea what is good for development. But some amount of stability is obviously essential - and this planet certainly has that.
Roll on the TPF (http://en.wikipedia.org/wiki/Terrestrial_Planet_Finder)!
Andy
-
The presence of a narrow strip that is neither hot enough to melt metal nor so cold that even a Geordie would put a coat on, with neither night nor day nor seasons, would probably not be good for development...
If you have an atmosphere the strip would not be narrow. We know nothing about the planets nutation/precession behaviour, which would also widen it. And vegetable life seems to like it here on the equator, where there are no seasons. And nobody knows yet if this planet has a moon, and therefore tides, or even if tides are critically important to biogenesis...
Of course, all this is hypothesising well in advance of the data. All I am pointing out is that the original suggestion that 'habitable-zone' planets are rare or non-existent is not borne out by current evidence, which suggests that they may be quite common. As soon as we obtain the technology needed to identify them we seem to find them.
I have commented earlier that the prevalence of life is a different question, and one more properly addressed by biochemistry than astronomy, as you suggest in much of your post. Though I am fairly optimistic, given (as I said before) that life started here almost as soon as it could. Intelligent life, however, seems to be another matter.....
(I only saw Dreadnought's comments after I had written the above - but I thought I would submit anyway - in support if nothing else...)
-
Intelligent life, however, seems to be another matter.....
Someday, maybe.........
Even equatorial areas have night and day, very sudden night if I recall right. Usually missed the start of the day.
In such a situation as the ribbon planet, the atmosphere, if any, might not be useful to any form of life beyond bacteria.
-
the atmosphere, if any, might not be useful to any form of life beyond bacteria.
Indeed, it may not be. There may well be no life there at all. The only point I was trying to make was that it is a planet in the habitable zone.
I suspect we will soon have more detailed descriptions of possible surface conditions on such a planet from the exobiologists and others. And I am fairly sure that these better informed descriptions will be shown to be comprehensively wrong when we finally get a probe there in a hundred years or so....
-
Oh and, just so people know what 'earth like' planet means, if the kepler mission had of been launched in another solar system looking towards our system, Venus and possibly even Mars, would be described as 'earth like.'
Venus has a surface temperature hot enough to melt lead and Mars is extremely cold.
As you were.
-
Life would find this similar to our rotating planet where it's hot on the equator while the poles are freezing.
I stopped reading at this laughable assertion. Life on the planet being discussed (or are you changing the parameters of the debate yet again?) ie Gliese 581 g, would not find it similar to our rotating planet.
But dont take my word for it, take New Scientists
"Conditions on the planet would be very different from those on Earth. The host star is a low-mass red dwarf that is just 1 per cent as bright as the sun.
Because it puts out so little light and warmth, its habitable zone lies much closer in than does the sun's. At such tight distances, planets in the zone experience strong gravitational tugs from the star that probably slow their rotation over time, until they become "locked" with one side always facing the star, just as the moon always keeps the same face pointed towards Earth.
That would mean perpetual daylight on one side of the planet and permanent shadow on the other. A first approximation suggests the temperature would be 71 °C on the day side and -34 °C on the night side, though winds could soften the differences by redistributing heat around the planet."
http://www.newscientist.com/article/dn19519-found-first-rocky-exoplanet-that-could-host-life.html
Of course further investigation would need to be done to confirm the range of temperatures on Gliese 581 g. It could be that the temperature range could be a lot higher but even so, Professor Vogt states the most temperate place would be the terminator.
Mind you, the same professor did state he was "100% certain" this planet has life.
-
Three points:
Tidal lock on bodies in elliptical orbits (which this planet surely has) always results in a process of libration - a gentle wobble around the lock point. It's the libration of the Moon, for example, that allows us on Earth to see 59% of the lunar surface, over time. For this planet, that "narrow strip" of comfortable living could, therefore, be quite extensive. The presence of an atmosphere - just about a "given", seeing the planet's mass and gravity are high - will somewhat negate the extremes of cold and hot, as heat will be transferred from the hot sun-facing "pole" to the cold "pole".
I very much doubt the terminator on this planet would be quite expansive. In fact, I'd say that's an incorrect assertion. The terminator will still represent only a very small part of the planet and an even smaller part of any landmass, even assuming that any landmass runs from pole to pole or part thereof.
As to tectonic conditions (and the suggestion of a Venusian-style atmosphere) we have no idea. The star is old, much older than the Sun, so radioactives in the planets will provide less heat than they used to. The stars metallicity is about half that of the Sun's, so again it's likely that these planets are more heavy-metal deficient than our own. That said, this new planet is big - three times the mass of the Earth and perhaps 50% bigger - so it will lose residual heat more slowly than the Earth, and this might mean a "normal" tectonic process is still on-going. We can't say either way that it is or isn't.
Gliese is described as a low mass dim red dwarf. As such, it emits something in the order of 1% of the light our sun does. But as you say, tectonic movement is a complete unknown at this point.
Finally: with one data point (the Earth) we really have little idea what is good for development. But some amount of stability is obviously essential - and this planet certainly has that.
Roll on the TPF (http://en.wikipedia.org/wiki/Terrestrial_Planet_Finder)!
Andy
I think we have far better examples more easily observable in our own solar system at this time.
-
..I stopped reading at this laughable assertion....
I, in turn, see little point in watching you squirm and try to change the basis of the discussion. You argued that 'habitable planets' were either vanishingly rare or non-existent. "Just to be clear," you said, "..I mean terrestrial sized planets in the habitable zone."
Is this a 'habitable planet' by your definition? The NS article you quote seems to think so:
"Astronomers have found the first alien world that could support life on its surface. It is both at the right distance from its star to potentially harbour liquid water and probably has a rocky composition like Earth..."
The primary point you made, that these planets must be very rare, was supported by your assertion that they were not being found. The same NS article states:
"The discovery suggests habitable planets must be common, with 10 to 20 per cent of red dwarfs and sun-like stars boasting them, the team says. That's because Gliese 581 is one of just nine stars out to its distance that have been searched with high enough precision to reveal a planet in the habitable zone."
Whether life exists on the planet or not is unknown. The surface conditions do not present an insuperable barrier. But current evidence suggests that, when we apply technology which is capable of finding them, these planets will turn out to be quite common, and NOT vanishingly rare...
QED
-
That would mean perpetual daylight on one side of the planet and permanent shadow on the other. A first approximation suggests the temperature would be 71 °C on the day side and -34 °C on the night side, though winds could soften the differences by redistributing heat around the planet."
As a point of interest, the record maximum/minimum temperatures recorded for the Earth are around +60°C and -90°C. And those are figures measured in the shade with an atmosphere. Estimates for Gliese 581 g seems to be somewhat balmier than here....
-
Ironically, in view of the conversations above, I note that at a conference currently running in Torino (The Astrophysics of Planetary Systems: Formation, Structure, and Dynamical Evolution) doubt is being cast on the the existence of Gliese 581 g. Another team has been looking at their data, and say that they cannot confirm the first team's findings. At present it has been demoted to 'unconfirmed'. http://www.space.com/scienceastronomy/doubt-cast-habitable-alien-planet-gliese-581g-101012.html refers.
All these findings are at the limit of what we can do with our current technology (which is improving rapidly as we speak). But most of the data that we need for these findings HAS to be spread over time, so we have to depend on 10 year old data. It is tantalising to have to wait, but wait we must, as I have indicated earlier. I expect that the next several years will bring a wealth of information about smaller planets which we are currently unable to detect...
-
http://www.newscientist.com/article/dn19586-first-lifefriendly-exoplanet-may-not-exist.html
Oh dear! Didnt someone say 'the evidence is growing that earth like planet are quite common' or near as damn it? %%
I see someone is doing the backstroke already! Never mind!
The current evidence suggests earth like planets are very rare. If any one cares to read the 'Rare Earth' they'll start to grasp why our earth and solar system are tending towards uniqueness.
-
Oh dear! Didnt someone say 'the evidence is growing that earth like planet are quite common' or near as damn it? %%
I see someone is doing the backstroke already! Never mind!
Yes - the same magazine that you seem to depend upon for all your astronomical stories.
The current evidence suggests earth like planets are very rare....
No it does not. There is inadequate current evidence to pronounce on the 'rare earth' hypothesis, because detecting earth-like planets is at or just beyond the limits of our current observing technology. This episode is a good example of that.
The report goes on to say: "..Although the Geneva team cannot find evidence for the new planet, they cannot exclude the possibility that Gleise 581 g exists....Steven Vogt... added that the negative result is not entirely unexpected. "I am not overly surprised by this as these are very weak signals..."
I am sure you remember this report on the amplifier problems with Kepler - http://www.universetoday.com/43856/no-earth-sized-planet-hunting-for-kepler-until-2011/ - indicating that habitable-zone planet detection would be very difficult until next year. Though there may be none, it is misleading to suggest that 'the evidence shows them to be rare' until there has been a suitable opportunity to detect a fair number and none are detected. Saying that they are likely to be rare or non-existent at this stage is pure speculation.
-
Yes - the same magazine that you seem to depend upon for all your astronomical stories.
So what's your point here? That I have on occasions referenced NS? Just to show up another of your inaccurate statements or 'spin' in various threads I have referenced other sources. Just because its not the 'science paper' you expect to support a post in a model boat general chat forum. Get a life, mate.
No it does not. There is inadequate current evidence to pronounce on the 'rare earth' hypothesis, because detecting earth-like planets is at or just beyond the limits of our current observing technology. This episode is a good example of that.
The report goes on to say: "..Although the Geneva team cannot find evidence for the new planet, they cannot exclude the possibility that Gleise 581 g exists....Steven Vogt... added that the negative result is not entirely unexpected. "I am not overly surprised by this as these are very weak signals..."
I am sure you remember this report on the amplifier problems with Kepler - http://www.universetoday.com/43856/no-earth-sized-planet-hunting-for-kepler-until-2011/ - indicating that habitable-zone planet detection would be very difficult until next year. Though there may be none, it is misleading to suggest that 'the evidence shows them to be rare' until there has been a suitable opportunity to detect a fair number and none are detected. Saying that they are likely to be rare or non-existent at this stage is pure speculation.
You see, there you go again, trying to stifle the debate! A hypothesis is "a proposition, or set of propositions, set forth as an explanation for the occurrence of some specified group of phenomena, either asserted merely as a provisional conjecture to guide investigation (working hypothesis) or accepted as highly probable in the light of established facts." The Rare Earth fits that description but Im sure you will provide a science paper to argue different though.
Bottom line though, as you constantly appear to forget, is that this is a general chat forum not the astronomical society or whatever you seem to think it should be.
There's no requirement for scientific papers to support ones opinion here. You seem to hang on to the belief that millions of planets like earth (please note I said like earth not earth like) are out there in the Milky Way waiting to be discovered. I think you're going to be disappointed when Kepler's mission results are published. I think there may be the odd ones but they'll be too hot, too cold, in too eccentric an orbit etc.
You may be right. Time will tell but then again, I didnt waste something of the order of nearly 200 computing years (20 headless pc's wasnt it working all day, every day for nearly 10 years?) in the vain hope of finding an ETI signal then, giving up realising at last what a complete waste of time, resources and money the whole thing was. LOL!
-
The current evidence suggests earth like planets are very rare.
There's no requirement for scientific papers to support ones opinion here.
How can you claim that current evidence suggests that earth-like planets are very rare, and then say that there is no requirement to provide that evidence? Current evidence simply does not support your assertions.
-
How can you claim that current evidence suggests that earth-like planets are very rare, and then say that there is no requirement to provide that evidence? Current evidence simply does not support your assertions.
Oh dear, you simply cannot read or, deliberately alter what others have said!
I said there was no need to produce scientific papers to support one's opinion here. You clearly have a problem understanding simple English.
I've noticed you have tried to use the argument that I have changed my opinion a few posts back. Yet another desparate attempt by you to try and and show an inconsistency where none exists. My opinion hasnt changed one jot. You, on the other hand, have merely used a couple of sentences that mean essentially the same thing but which I had phrased slightly differently.
Im more than happy to confirm to you my position and stance hasnt changed one jot. Current evidence does support my opinion that Earth like planets are very rare.
-
Im more than happy to confirm to you my position and stance hasnt changed one jot. Current evidence does support my opinion that Earth like planets are very rare.
And that evidence is?
-
Yet again, further evidence that our solar system is tending to uniqueness.
http://www.bbc.co.uk/news/science-environment-12333766
A solar system including six planets around a star 2,000 light-years away has been spotted by astronomers.
The planets range between two and four-and-a-half times the radius of Earth, and between two and 13 times its mass.
Five of the planets orbit the star closer than Mercury orbits our Sun.
All of the planets orbit their host star closely - five of them closer to their star than Mercury is to our Sun, and the sixth just beyond that distance. Two orbit at a distance just one-tenth as far as the Earth is from the Sun.
What is surprising is that all the planets are comparatively large; the system has a total of 10 times the mass of the Earth inside the radius of Mercury's orbit; here in our Solar System, there are only about two Earth masses contained in a radius five times that of the Earth's orbit.
-
No, yet again this is early evidence extrapolated, by you, to suggest a bigger picture that may well not be the case.
I give up.
Andy
-
No, yet again this is early evidence extrapolated, by you, to suggest a bigger picture that may well not be the case.
I give up.
Andy
It will be no surprise to find that I am in agreement with dreadnought72 - I would also point out that the first Kepler candidate planets for which we have had data released had orbital periods of a few hours or days.
These current candidates have orbital periods of around 10-50 days, and are correspondingly further out. It has been pointed out at some length that the first discoveries would be the short-period ones, and we will have to wait for the longer period planets in the habitable zone. It seems to me that Kepler is proceeding according to schedule - first the 1 day length orbits, and now the 50 day orbits. I assume another six months or so will be giving us some 100-200 day orbit candidates, and then we will start being able to talk about earth-like planets. Until then, ALL the Kepler findings will by definition be unlike the Solar System....
-
Hi,
When my daughter was doing a school science project some years ago, in order to get some visual perspective of the solar system, we made a tiny 2mm diameter "model" of the Earth, covered a netball (850mm dia.?) with yellow tissue paper to represent the Sun and placed them 25 metres apart in the garden. It was almost a profound experience seeing the vast emptiness of space even within the Earth's orbit (it also showed how unlucky we were to be hit by a giant meteor!).
When the scientists describe these vast Jupiter size planets within the orbital distance of Mercury, it seems that it would be too crowded of have six of them, but, having built the "model" described above, it does allow one to have an appreciation of the size of the Universe that no amount of equations, books, TV images and the like, can give you.
Ian.
-
Hi,
When my daughter was doing a school science project some years ago, in order to get some visual perspective of the solar system, we made a tiny 2mm diameter "model" of the Earth, covered a netball (850mm dia.?) with yellow tissue paper to represent the Sun and placed them 25 metres apart in the garden...
Those figures seem a little out to me. They suggest that the Earth is about 30 sun diameters away from the sun, which is much too short a distance? In reality it's about 100 diameters away. Without doing the calculation, I would guess that the netball should be about 30mm diameter, or the distance should be about 80m....
...(it also showed how unlucky we were to be hit by a giant meteor!)...
Of course you have to allow for the fact that, from time to time, clouds of debris pass through our orbital position. These clouds are orbiting the sun in a similar fashion to ourselves, thus making contact more likely. The early years of the Solar System featured quite a lot of impacts, as the surface of the moon indicates. http://en.wikipedia.org/wiki/Late_Heavy_Bombardment gives an example...
-
Using the materials and space available, it was a pretty good representation of the scale of things, and perfectly good for perception of the way things are in our system. Much better than an astrolabe, even if the relative motions could not be shown. No doubt many people still think of the relative sizes and spacings as being accurately depicted in the drawings on encyclopaedia pages in the manner of an engineering drawing for construction of a new one.
Any chance of taking the overall diameter of the netball as being the Sun and its corona?
-
Using the materials and space available, it was a pretty good representation of the scale of things...Any chance of taking the overall diameter of the netball as being the Sun and its corona?
I don't think there is any agreed diameter for the corona. It varies in size, of course, sometimes down to near-zero and back out to about 1 solar radius, so you could certainly have the netball as the corona. :-)) :-))
It's definitely a much better representation of the Solar system than the usual encyclopedias give, so I'm certainly not knocking it... In practice, of course, if you try to make a really accurate representation, even of the crowded area of space around our sun, you soon run into practical difficulties. At your scale, Saturn would be about 250yds away, and Neptune about half a mile....
-
Hi,
Whoops - Obviously not many netball players on Mayhem then!
I meant to say the Netball was about 220mm diameter, I must of been thinking of the Sun's diameter of 860,000 miles. I think the 850mm Netball is reserved for the alien netball players on the recently discovered giant worlds!
If we take the 25 metres as representing the 93 million miles between the Sun and the Earth (excuse the mix of units) then the Earth would be about 2mm and the Sun 215mm, which is about right.
If you visit the Kent village of Otford (just north of Sevenoaks), there is the Millenium Solar System ( http://www.otford.org/solarsystem/ ), which provides annother perspective of space.
Ian.
-
No, yet again this is early evidence extrapolated, by you, to suggest a bigger picture that may well not be the case.
I give up.
Andy
Give up? I thought you had just started looking?
Seems like this person has no problem extrapolating information to support his view point ""The fact that we've found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting sun-like stars in our galaxy," said William Borucki of NASA's Ames Research Center" And you know what, I dont disagree with him because likely there are many planets.
Seriously, no its not early evidence whatsoever. But you keep thinking these results may well not be the case.
It is further evidence that what is out there is pointing in the direction that our solar system isnt common.
Of some of the earth sized planets discovered by Kepler and recently announced by NASA "Five of the potential planets are near Earth-size and orbit in the habitable zone of smaller, cooler stars than our sun. ie even these solar systems are different.
-
Hi,
When my daughter was doing a school science project some years ago, in order to get some visual perspective of the solar system, we made a tiny 2mm diameter "model" of the Earth, covered a netball (850mm dia.?) with yellow tissue paper to represent the Sun and placed them 25 metres apart in the garden. It was almost a profound experience seeing the vast emptiness of space even within the Earth's orbit (it also showed how unlucky we were to be hit by a giant meteor!).
When the scientists describe these vast Jupiter size planets within the orbital distance of Mercury, it seems that it would be too crowded of have six of them, but, having built the "model" described above, it does allow one to have an appreciation of the size of the Universe that no amount of equations, books, TV images and the like, can give you.
Ian.
Further analysis of these 6 large planets that orbit so close to the star is required to determine if they 'grew' in the position they currently occupy or, formed further out and migrated inwards.
Either way, its yet another exo system unlike our own.
-
...Either way, its yet another exo system unlike our own...
ALL the early Kepler detections MUST be unlike our own system, because they are detecting CLOSE-IN planets first. So ALL the first detections will show planets much close in than ours.
Now, there may be no planetary systems out there with worlds similar in size to the Earth, orbiting a star the same size as ours at between 300 and 400 days orbital period. Or there may be lots. We just can't tell until Kepler has been looking long enough to detect these. Kepler CANNOT find ANY of these with the data it currently has, so it's not surprising that it has found none. The fact that it has found short-period planets says absolutely NOTHING about the possibility of finding long-period planets later.
The time to have an opinion about earth-type planets based on evidence will be towards the end of this year. Until then, any opinion is simply speculation.
-
If we take the 25 metres as representing the 93 million miles between the Sun and the Earth (excuse the mix of units) then the Earth would be about 2mm and the Sun 215mm, which is about right.
Whoops - sorry! I estimated the Sun at 30mm, when it should have been 30cm.
I hate SI..... :(( :((
-
Some interesting information. So, Kepler has increased the number of exo planets found todate which was to be expected. The number of exo planets has increased from around 400. From the article it looks like kepler has found another 1235. That seems to suggest the total number of exo planets stands at over 1600?
Its important to understand however that most of these 'exo planetary' finds are candidates which means they could be large asteroids etc and further investigation is required to confirm them as exo planets.
Despite this, very few multiple planetary systems have been found, in the region of 170 exo solar systems with 2 or more planets. Only 68 of kepler's 1235 exo planet candidates are less than 1.25 times the width of Earth. A mere 2 dozen appear less than the width of the Earth.
Of planets found in the HZ of a star, only 5 are small enough to be rocky like the Earth (according to this article).
The kepler data or at least all the articles I've read so far, none of the host stars with planets in the HZ appear to be main sequence stars like our own and, are perhaps more red dwarfs?
http://www.newscientist.com/article/dn20079-found-dozens-of-planet-candidates-smaller-than-earth.html
NASA's Kepler space telescope has found the smallest planet candidates yet, some of which are even smaller than Earth. It has also spotted 54 planet candidates in the habitable zones of their stars, where liquid water – and therefore perhaps life – could exist on the planets' surfaces.
Kepler launchedMovie Camera in 2009 on a mission to determine how common Earth-sized planets are in the habitable zones of their stars. It detects planets by watching for the slight dimming that results when a planet passes in front of its parent star as seen from Earth – an event called a transit.
Now, mission scientists say they have found 1235 planet candidates in data taken during the telescope's first four months of observations, from mid-May to mid-September 2009. Kepler has continued to make observations since then, but team members are still analysing the data.
The newly announced candidates include:
68 roughly Earth-sized candidates, each less than 1.25 times as wide as Earth
288 super-Earth candidates, between 1.25 and 2 times the size of Earth
662 Neptune-sized candidates
184 Jupiter-sized or larger candidates
170 possible multi-planet systems, with two or more candidates orbiting the same star
About two dozen of the candidates appear to be smaller than Earth. Some of these are about the size of Mars – which is half the size of Earth – said Kepler's chief scientist, William Borucki of NASA's Ames Research Center in Moffett Field, California. If confirmed, these would be by far the smallest planets ever found around normal stars. The current record is a confirmed planet found by Kepler that is 1.4 times Earth's width.
Of the planets in the habitable zones of their stars, five are small enough to be rocky like Earth, spanning between 0.9 and 2 times our planet's width. The others are giants like Neptune or Jupiter, which have no solid or liquid surface on which life could take hold. But these could still have Earth-sized moons that are habitable, Borucki said.
-
The kepler data or at least all the articles I've read so far, none of the host stars with planets in the HZ appear to be main sequence stars like our own and, are perhaps more red dwarfs?
Red Dwarfs are Main Sequence stars - they are just further along in their life span. We are a G type star - when considering star types which might support life on their planets it is common to consider F, G and K as possibilities, eliminating O, B, A and M.
I don't think the Kepler team are providing the star types for all their candidates, and would be interested to see a reference if there is one. Quite a lot (most?) planets seem to be being found round F, G and K types - it seems to be where astronomers look!
Looking at F, G and K types, you would expect the HZ to be at about 300-400 days orbit, so they will not occur yet in the Kepler data. The only planets which are in the HZ with a 50 day or less orbit will be going round small stars.
Once we have Kepler data which covers a 1-2 year orbit we will start to detect Earth-type planets. Or not. Either way, we really cannot expect to see any at the moment, or draw any conclusions from the fact that there are few currently known...
-
As someone who finds the complexity of our own planet difficult to digest, never mind the composition and vagaries of "possible" planets that have yet to be discovered, and as a rather bemused reader of this topic....I'm at a total loss as to where it's all going.
First of all, will someone please (in words of one syllable, if that's possible) explain just what "Kepler" is. Is it an Earth based and purely scientific electronic programme, or is it based on something like an up-graded "Hubble" sort of thing? Or is it a combination of the two.
The definitions of "life" seem to zap between some sort of humanoid (be it carbon, silicon or even granite based) and something more akin to a lichen. You'll be discussing Triffids next I suppose. And as for that rather weird discussion about brain sizes...surely it isn't the physical size of the brain, but what it's capable of doing. And how quickly (which leaves me out).
But where do the regulars on this topic visualise the eventual outcome? Or is it going to just meander on until the end of "time" as we know it?
Just a simple (ex) sailor asking a question. BY.
-
First of all, will someone please (in words of one syllable, if that's possible) explain just what "Kepler" is. Is it an Earth based and purely scientific electronic programme, or is it based on something like an up-graded "Hubble" sort of thing? Or is it a combination of the two.
You can look for planets going round other stars in lots of ways. The most common one for ground-based telescopes involves looking for the slight wiggle the star makes as a planet goes round it. This will generally pick up big planets that cause a big wiggle, but won't find small ones.
You could find small ones by looking for the slight dimming of the star as a small planet passes in front of it, but the variations in the atmosphere make that tricky to do from the ground. If you send up a space telescope that problem goes away, and you can then find small planets. The way you do this is to stare at some stars for a long time, and if you get regular dips in brightness you can can calculate that there is a planet there. If a planet orbits in 10 days you probably have to look for about 30 days to confirm this - if it orbits in 1 year you need to look for about 3 years...
That's what we've done. The space telescope is called Kepler, and it is in orbit round the sun, a comfortable distance from Earth. It was launched in 2009, and started reporting short-period planets in 2010. It found a lot, and so there is quite a lot of interest in it. The rest of the project sits on the Earth, and does a lot of calculation. We have data on planets with orbits up to about 50 days at the moment...
And as for that rather weird discussion about brain sizes...surely it isn't the physical size of the brain, but what it's capable of doing.
Yup, that's true.
But where do the regulars on this topic visualise the eventual outcome? Or is it going to just meander on until the end of "time" as we know it?
Oh, no! A lot longer than that...
-
Well thanks for that. As always a lucid reply from the Dodgy Geezer.....but...and there's always a "but".
I was always taught that stars were so far away that any magnification would only result in a larger "dot", as opposed to a nearby planet that could be magnified.
And to be honest, I more or less still believe that to be a truism. So from what your'e telling me, do I gather that stars so far distant that the human brain can't comprehend the distances involved are now being observed as more than just points of light?
Even if that's the case, then that light comes from so far away that "we" are only seeing what was once was. And that makes a nonsense of all the postulations aired on this thread.
I keep reading about "chances of life" being found on planets orbiting a star (or galaxy, even) but without much regard for the fact that the light being observed pre-dates any lfe on our lump of rock by the number '1' followed by more zeros than this forum could handle.
So my conclusion is that for all the posturing and sometimes pseudo-science that's been promulgated, you're all talking out of the back of your heads.
Prove me wrong. BY.
-
I was always taught that stars were so far away that any magnification would only result in a larger "dot", as opposed to a nearby planet that could be magnified.
And to be honest, I more or less still believe that to be a truism. So from what your'e telling me, do I gather that stars so far distant that the human brain can't comprehend the distances involved are now being observed as more than just points of light?
Err...yup. Here are two images you might find interesting: the surface of Betelgeuse (http://www.universetoday.com/50407/unprecedented-images-show-betelgeuse-has-sunspots/) and three planets in orbit around Fomalhaut (http://www.msnbc.msn.com/id/27702538/ns/technology_and_science-space/)
Fomalhaut is about 25 light years away, Betelgeuse about 500. The Betelgeuse picture was taken using a 'long baseline interferometry' technique. This is a trick to get more resolution. Resolution depends on the diameter of the lens aperture, but it is hard to make a very wide lens/mirror. Instead, we can use two telescopes together and pretend that each one is a bit of a giant lens which is stretched between them. The Betelgeuse picture was taken using one telescope in Arizona and another just outside Paris - making an apparent 5000 mile wide lens. When we start doing this kind of thing in space we will effectively have lenses many millions of miles wide....
Even if that's the case, then that light comes from so far away that "we" are only seeing what was once was. And that makes a nonsense of all the postulations aired on this thread.
I keep reading about "chances of life" being found on planets orbiting a star (or galaxy, even) but without much regard for the fact that the light being observed pre-dates any lfe on our lump of rock by the number '1' followed by more zeros than this forum could handle.
The distances involved aren't particularly great. You can think about our Solar System as our back yard, our Galaxy as our town, and other Galaxies as other countries. We are wandering about in our Solar System now, and looking at stars near to us in our Galaxy. Here is a link (http://en.wikipedia.org/wiki/List_of_stars_with_confirmed_extrasolar_planets) to a list of confirmed exo-planets. You will see that their distances vary between 20 light years and about 5000 light years - most are less than 100 light years away. That's not a very long time ago....
[/quote]
-
One hundred light years is not so long ago? Yeah, feels like yesterday. I'm not even going to bother getting my calculator out for that one....I just know there'll be a lot of zeros on the end of it.
And that's a close one? Really, just what are you trying to achieve here?
I'm (honestly) trying to be serious about all this....believe it or not. But if you send out a signal to Betelguese now, that may or well not have blasted itself into smithereens over 100 light years ago....just where do you think your signal is going to be picked up at? And when? And then, will we still be here to receive the reply?
I can understand the reasoning behind the research, but for the life of me I can't understand how some people think there's even a remote possibility of getting actual communication. Pie in the sky.
We may or may not be the only sentient beings in this cosmos....but as sure as God made little apples, we ain't going to be able to talk to them. BY.
-
One hundred light years is not so long ago? Yeah, feels like yesterday. I'm not even going to bother getting my calculator out for that one....I just know there'll be a lot of zeros on the end of it.
And that's a close one? Really, just what are you trying to achieve here?
I'm (honestly) trying to be serious about all this....believe it or not. But if you send out a signal to Betelguese now, that may or well not have blasted itself into smithereens over 100 light years ago....just where do you think your signal is going to be picked up at? And when? And then, will we still be here to receive the reply?
Um? Who said anything about communicating? I certainly didn't. We were talking about examining the stars in our current locality to determine if they have planets. We may go on from there to see if we can detect any form of life on them - perhaps looking for radio activity or analysing their atmospheres, both of which are things we could do with current or near-future technology. We would, of course, be examining a planet between 5 and a few hundred years in the past, but I can't see that that will make a lot of difference to the results of the analysis.
I would anticipate that sometime in the next 50 years we will be thinking of sending a probe to the nearest stars - perhaps a 10-year trip at 0.5 light speed. It seems like a good idea to have a look at them first and decide which ones look interesting....
P.S. Did you like the pictures?
-
I see before me a list of columns and numbers that I neither understand or have any intention of ploughing through....no thanks, life (on this world, at least) is too short for all that. Betelguese didn't look like that through my old sextant thank goodness!
I really didn't understand the Jeanna Brynar pictures. Very pretty, as are all the photos I've seen of the "void" called "space". But basically meaningless to a pleb like me.
Yes, perhaps you as an individual didn't specifically mention "communication" with ET...but others on this thread certainly have. Two camps here...one is to leave it well alone, and the other to welcome it. Can't get much more polarised than that.
Actually, I'm quite keen on the idea of inter-stellar exploration, if only to increase the sum total of human knowledge...if such knowledge can make "people" draw back from the self destructive path we seem hell bent on pursuing.
But some of the respondents on this thread seem to delight in delving into the realms of fantasy, whilst others require a Masters Degree in astro-physics to even get a glimmer of understanding.
But...and always another "but"...there's a glaring hiatus within this entire thread. And that's the perceived influence of "religion".
Not that I want to get anywhere close to that subject, but the very idea of a "God" does pervade the human psyche, and as such should be allowed a certain amount of credence when the physical/metaphysical aspects of this particular universe is being discussed. BY
-
I see before me a list of columns and numbers that I neither understand or have any intention of ploughing through....no thanks, life (on this world, at least) is too short for all that. Betelguese didn't look like that through my old sextant thank goodness!
I really didn't understand the Jeanna Brynar pictures. Very pretty, as are all the photos I've seen of the "void" called "space". But basically meaningless to a pleb like me.
Yes, perhaps you as an individual didn't specifically mention "communication" with ET...but others on this thread certainly have. Two camps here...one is to leave it well alone, and the other to welcome it. Can't get much more polarised than that.
Actually, I'm quite keen on the idea of inter-stellar exploration, if only to increase the sum total of human knowledge...if such knowledge can make "people" draw back from the self destructive path we seem hell bent on pursuing.
But some of the respondents on this thread seem to delight in delving into the realms of fantasy, whilst others require a Masters Degree in astro-physics to even get a glimmer of understanding.
But...and always another "but"...there's a glaring hiatus within this entire thread. And that's the perceived influence of "religion".
Not that I want to get anywhere close to that subject, but the very idea of a "God" does pervade the human psyche, and as such should be allowed a certain amount of credence when the physical/metaphysical aspects of this particular universe is being discussed. BY
Interesting! On a couple of points.
I find it disappointing that anyone wants to raise religion in this thread. IMHO, it has no place in this thread which was started as a purely 'astrological' one. I could well imagine someone starting a religious thread being, rightly, upset if they started such a thread and astronomy was introduced as an alternate view.
Never mind.
In both this thread and the 'There's no one out there!' thread, I hoped it would be as you say, in plain ordinary language that doesnt get bogged down in too technical explanations or demands. Unfortunately, again, IMHO, one or two notable posters seem to have gone out of their way to do just that ie technical terms and demands of scientific papers to support a number of posts or argue down an alternative view.
Again, hey ho.
Regarding Kepler, I find these comments interesting. Although I cannot say they are directly attributable or made by anyone connected to the Kepler Mission, the information appears to be Kepler based.
These comments are "On 2 February 2011, the Kepler team announced the results from the data of May to September 2009. They found 1235 planetary candidates circling 997 host stars, more than twice the number of currently known exoplanets. This haul included 68 planetary candidates of Earth-like size and 54 planetary candidates in the habitable zone of their star. They estimate that 6% of stars host Earth-size planets and 19% of all stars have multiple planets."
I have bolded that last sentence. So, it seems that when it suits, extrapolation on a (relatively) small sample is ok. But, there we have it, 6% of stars could host Earth size planets. Of course that figure could increase. But it could just as easily decrease.
Im not going to do the maths but its reasonable to assume that not all those Earths are going to be in the habitable zone of their host star. Hmmmmmmmmm.
EDIT Forgot this "All of the habitable zone candidates found thus far orbit stars significantly smaller and cooler than the Sun (habitable candidates around Sun-like stars will take several additional years to accumulate the three transits required for detection)."
-
I find it disappointing that anyone wants to raise religion in this thread. IMHO, it has no place in this thread which was started as a purely 'astrological' one. I could well imagine someone starting a religious thread being, rightly, upset if they started such a thread and astronomy was introduced as an alternate view..........In both this thread and the 'There's no one out there!' thread, I hoped it would be as you say, in plain ordinary language that doesnt get bogged down in too technical explanations or demands. Unfortunately, again, IMHO, one or two notable posters seem to have gone out of their way to do just that ie technical terms and demands of scientific papers to support a number of posts or argue down an alternative view.
I have no problem with anyone who may want to talk about a religious sense of awe when considering the makeup of the universe. But I would disagree if, for instance, that person went on to say that, because of this religious dimension, exploration of the universe should be curtailed. I am thankful that this does not seem to be the case. Similarly, I have no difficulty with anyone who wants to avoid any discussion they consider technical, but I would not accept this being used as a justification to push theories which are technically inaccurate. And I rather hope that this thread started as an 'astronomical' one....
These comments are "On 2 February 2011, the Kepler team announced the results from the data of May to September 2009. They found 1235 planetary candidates circling 997 host stars, more than twice the number of currently known exoplanets. This haul included 68 planetary candidates of Earth-like size and 54 planetary candidates in the habitable zone of their star. They estimate that 6% of stars host Earth-size planets and 19% of all stars have multiple planets." ....................Im not going to do the maths but its reasonable to assume that not all those Earths are going to be in the habitable zone of their host star.
Astronomer Seth Shostak has done the maths for you. He estimates that "within a thousand light-years of Earth" there are "at least 30,000 of these habitable worlds." But these are still early days and there seems to be little point in guessing at numbers when we are quite close to getting concrete data.
-
In truth, I've enjoyed this topic...insofar as I could understand it. Nothing wrong with that, never too late to learn.
The only reaso I brought the dreaded word "Religion" into the discussion was because ever since mankind became sentient he's looked at the skies and "wondered" what it was all about. Various bits of mystique was eventually attached to the heavens, and so all sorts of stuff came about that eventually coalesced into the word "Religion". I wish it had another word in this context! Nothing whatsoever to do with the pomp and ceremony of how "religion" is now practised.
Anyone who has been lucky enough to look up into a full starlit sky....even in this year of 2011...must have had a few moments of private cogitation. More or less on the lines of "What if"?
Theologians, Cosmologists, Physicists and Astronomers all seem to just carry on ploughing their own furrow disregarding other ideas. Perhaps with the exception of people like the late Fred Hoyle who appeared to embrace just about everything. And nothing wrong with that, either. Must have confused the hell out of him though. BY.
-
I have no problem with anyone who may want to talk about a religious sense of awe when considering the makeup of the universe. But I would disagree if, for instance, that person went on to say that, because of this religious dimension, exploration of the universe should be curtailed. I am thankful that this does not seem to be the case. Similarly, I have no difficulty with anyone who wants to avoid any discussion they consider technical, but I would not accept this being used as a justification to push theories which are technically inaccurate. And I rather hope that this thread started as an 'astronomical' one....
You once again labour under a misunderstanding. I find that unsurprising given your repeated attempts to hijack this and other threads. But you carry on if you must.
Astronomer Seth Shostak has done the maths for you. He estimates that "within a thousand light-years of Earth" there are "at least 30,000 of these habitable worlds." But these are still early days and there seems to be little point in guessing at numbers when we are quite close to getting concrete data.
That'll be the same Seth who claims seti will 'discover' the first ETI signal within the next 25 years? :-))
-
In truth, I've enjoyed this topic...insofar as I could understand it. Nothing wrong with that, never too late to learn.
The only reaso I brought the dreaded word "Religion" into the discussion was because ever since mankind became sentient he's looked at the skies and "wondered" what it was all about. Various bits of mystique was eventually attached to the heavens, and so all sorts of stuff came about that eventually coalesced into the word "Religion". I wish it had another word in this context! Nothing whatsoever to do with the pomp and ceremony of how "religion" is now practised.
Anyone who has been lucky enough to look up into a full starlit sky....even in this year of 2011...must have had a few moments of private cogitation. More or less on the lines of "What if"?
Theologians, Cosmologists, Physicists and Astronomers all seem to just carry on ploughing their own furrow disregarding other ideas. Perhaps with the exception of people like the late Fred Hoyle who appeared to embrace just about everything. And nothing wrong with that, either. Must have confused the hell out of him though. BY.
Yep, me too. Apart from a couple of people spoiling the thread and using comments such as "I would not accept this being used as a justification to push theories which are technically inaccurate."
Methinks someone's brain is off with the fairies again dreaming up such falsehoods.
-
I suppose it might not be inaccurate to say 'God knows what the truth of all this is.'
Colin
-
I suppose it might not be inaccurate to say 'God knows what the truth of all this is.'
Colin
Probably. I guess it depends on one's outlook of subjects on message boards. Unfortunately some people want to turn them into a scientific master class or maybe just a vain attempt to prove their superiority rather than accept it for what it is ie a place for debate rather than proving one way or the other with the aid of complex technical argument.
If that's their opine, then perhaps they should stick to places where their technical argument is welcomed and not used as a tool to stifle debate?
-
Yep, me too. Apart from a couple of people spoiling the thread and using comments such as "I would not accept this being used as a justification to push theories which are technically inaccurate."
Methinks someone's brain is off with the fairies again dreaming up such falsehoods.
As I recall, this thread started with you claiming that Earth-type planets would be vanishingly rare for a technical reason - the migration of Hot Jupiters. Then you claimed that the early Kepler data showing short-period planets also indicated that Earth-types in the Habitable Zone were rare.
I, and others, pointed out the technical inaccuracies in these assertions. Your response seems to be that this is ruining the thread for you. I see it as preventing opinion and journalist's reports masquerading as proven data...
-
As I recall, this thread started with you claiming that Earth-type planets would be vanishingly rare for a technical reason - the migration of Hot Jupiters. Then you claimed that the early Kepler data showing short-period planets also indicated that Earth-types in the Habitable Zone were rare.
I, and others, pointed out the technical inaccuracies in these assertions. Your response seems to be that this is ruining the thread for you. I see it as preventing opinion and journalist's reports masquerading as proven data...
This is interesting considering the backstroking going on above. And I love the way you try and make out a post on a model boat forum is an attempt, in any way shape or form, definitive of the situation.
Yes, of course I posted below and included a point of reference for people to read. However, you seem to have appointed yourself forum policeman on the subject. Do that if it gives you a sense of purpose in some small way.
The fact of the matter, as I have pointed out numerous times, is, this is a forum for debate. Instead you attempt to turn it into a science lesson.
For reference this is my original post
Kepler mission adds more weight to our solar system not being the norm.
« on: August 29, 2010, 10:36:56 AM »
Reply with quote
The much vaunted Kepler mission continues to provide evidence that our solar system is tending towards uniqueness rather than the norm.
Prior to Kepler's launch, virtually every exoplanetary system and exoplanets, were hot jupiters. That is, massive planets the size of jupiter or larger and, orbiting their parent star in a matter of days since they were so close to it.
Simulations have shown that where a hot jupiter planet exists very close to its parent star, it must have migrated in from further out. Hot jupiters cannot form close in to a star as there just isnt enough material for them to form. Instead, they must form further out in a system where there is more gas, elements and material required to form planets of their size.
The simulations show where hot jupiters migrate inwards, smaller terrestrial sized planets, if they existed in the system, would be ejected from that solar system.
http://www.telegraph.co.uk/science/space/7966992/Three-vast-planets-found-orbiting-distant-star.html
Now, we have this
http://www.telegraph.co.uk/science/space/8336500/Alien-life-boost-after-Nasa-finds-one-in-two-Suns-has-Earth-like-planets.html
The news came from NASA scientists studying the results from the Kepler telescope which in its first two years in space has found evidence of more than 1,200 planets in orbit around far distant stars.
The early findings suggests that there are triple the number of known planets outside our own solar system - 54 of them are Earth size and in the habitable zones from their suns.
Only two potentially habitable planets have previously been found outside earth's solar system, so Kepler scientists are very excited at finding so many possible candidate planets.
Speaking at the American Association for the Advancement of Science, Kepler chief scientist William Borucki said: "I am really delighted that we are seeing so many candidate planets and that means there is a rich ocean of planets out there to explore.
"For every two stars we are seeing a candidate planet."
The next step is to send out new telescopes to see if the atmospheres of the planets, that are between 30 and 100 light years away, have friendly atmospheres on which life could survive.
It is another big step to prove that a confirmed planet has some of the basic conditions needed to support life, such as the proper size, composition, temperature and distance from its star.
More advanced aspects of habitability such as specific atmospheric conditions and the presence of water and carbon require telescopes that are not built yet.
-
Kepler was a dunce. every one knows that the Klingon's exist and that the Mars men tried to invade earth but were defeated by earth bound bacteria...I mean Holly Wood cant be wrong !!! Can it??? ... O0 {-) %% ... Seareously ...Do you honestly beleave that We are the only intelagent life form in the whole unaverse.... I think not... the odds are much to long ... How can anyone say there is no life out there when we can't even count the sun's out there let alone the number of planets... This is the flat earth socitey all over again
Jimmy
-
Sorry chaps wrong button should have been the spell check
:D :embarrassed: :embarrassed:
Jimmy
-
...The fact of the matter, as I have pointed out numerous times, is, this is a forum for debate. Instead you attempt to turn it into a science lesson...
I see no debate on this thread. What I see is a succession of press reports culled mainly from the Telegraph science pages. And a running disagreement about the interpretation of early Kepler data which did not show planets at Earth-like orbits. Your view was that this showed that our system was abnormal and rare - others pointed out that Kepler needed time to find planets in wider orbits. I'm not sure why you think that constitutes a 'science lesson' which ought to be avoided...
Given that Jupiter takes 12 years to orbit once we will have to wait around 30 years to detect planets like this in Kepler data. The probe is unlikely to last that long. Nevertheless, the data coming in so far suggests that planets are quite common at all orbits, and I see nothing in the current data to suggest that Earth-like planets in the habitable zone will not be found when enough data has been collected.
Mr James' view that life is likely must wait on more data, of course. Nevertheless, none of the data gathered so far contradicts this possibility, and I anticipate that equipment capable of studying the atmospheres of close Earth-type planets should be available within 10 years...
-
Thanks D.G.
Jimmy
-
At last. Some science arrives:
http://xxx.lanl.gov/ftp/arxiv/papers/1103/1103.1443.pdf (http://xxx.lanl.gov/ftp/arxiv/papers/1103/1103.1443.pdf)
The digested results:
For F, G and K-type stars (i.e. those without excessive flares and old enough for life to develop), an Earth-analogue planet (0.8 to 2.0 times the size of the Earth) exists in the habitable zone (defined as 0.95 to 1.37 AU for a solar-luminosity star) ...
... 2.5% of the time.
This number may be revised up or down a little as Kepler works away for the next few years.
But it currently suggests that one in forty stars similar to the Sun have an Earth-analogue.
Over a billion in this galaxy. %%
Andy
-
At last. Some science arrives:
http://xxx.lanl.gov/ftp/arxiv/papers/1103/1103.1443.pdf (http://xxx.lanl.gov/ftp/arxiv/papers/1103/1103.1443.pdf)
The digested results:
For F, G and K-type stars (i.e. those without excessive flares and old enough for life to develop), an Earth-analogue planet (0.8 to 2.0 times the size of the Earth) exists in the habitable zone (defined as 0.95 to 1.37 AU for a solar-luminosity star) ...
... 2.5% of the time.
This number may be revised up or down a little as Kepler works away for the next few years.
But it currently suggests that one in forty stars similar to the Sun have an Earth-analogue.
Over a billion in this galaxy. %%
Andy
Interesting. Still early days, and I suspect that this was put out fast to gain publicity... but if the figures hold up it suggests that there could be a couple of 'Earths' within 50 LY of us. Lots more 'other' planets, of course, and this calculation does not take satellites of gas giants into account.
Of course, to have a proper discussion here we need to wait until this is reported in the Telegraph.... %)
-
A couple of Earths within 50ly would be more than I would have hazarded a guess at, myself - but any idea of uniqueness is certainly blown away. Meanwhile this paper's restrictions on the Earth-analogues are quite tight. As you say, they exclude gas giant satellites, and other scientists would certainly include a wider zone for habitability.
Maybe the Torygraph will catch up in a fortnight or so? ;)
Andy
-
A couple of Earths within 50ly would be more than I would have hazarded a guess at, myself...
Based on this atlas http://www.atlasoftheuniverse.com/50lys.html giving 133 visible stars within 50LY - the vast majority F/G/K. That suggests 3 Earths for 120 stars - I knocked one off to give a more conservative estimate. There are lots more low magnitudes, of course, but those are outside the definition...
If we go into more guesswork (rather than calculating probabilities based on volumes!) I might hazard that the nearest one will be about 30LY away. That figure tells us what size of detection apparatus needs to be created to examine an atmosphere at that distance, and hence what budget will be required...
This number may be revised up or down a little as Kepler works away for the next few years.
I suggest it is more likely to be revised up. The paper assumes that Kepler has found all planets that it is capable of so far - if for some reason or another this is not true, then the figure goes up. And it is only calculating for earth-type planets round an earth-type star - practical habitable planets may be found in other configurations. This figure represents a lower bound...
-
Well sorry not to have posted in here for a little while but I thought I'd let someone take a rest :}
The first of two posts, the second one is far shorter but just as enlightening.
Anyway, remember I said evidence is growing that our solar system is tending to uniqueness? No!? Then where have you been?
Ever heard of David Latham? No, neither had I! But, it turns out he has been asking the very same question. Well maybe not the very same question but unless you're a pedant, it amounts to the same thing.
"Two decades of searching have failed to turn up another planetary system like ours. Should we be worried?
IT WAS David Latham's misfortune that his email was time-stamped 1 April 1988. An astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, he was engaged in the then faintly disreputable task of searching for planets orbiting other stars. As he excitedly wrote to a colleague, he had found something: a body orbiting an ordinary yellow star, known only by its catalogue designation HD 114762, some 130 light years from Earth.
For Latham's peers, this was nothing more than an April Fool. If the object had been a planet, it would have gone against all we thought we knew about how planets - and indeed solar systems - could look.
Two decades on, planet-hunting is high fashion, and Latham has been vindicated. With hundreds of worlds known and more being discovered every week, planets and solar systems that break the rules are commonplace. In fact, they could well be the rule. It's time to ask the question: is our solar system actually the odd one out?"
and
"In 1995, Michel Mayor and Didier Queloz of the Geneva Observatory in Switzerland discovered a gas-giant planet with a mass similar to Jupiter's in a scorching four-day orbit around the sun-like star 51 Pegasi (Nature, vol 378, p 355). Within a year, Marcy and his colleague Paul Butler, both then at San Francisco State University in California, had confirmed that discovery, and also found two more "hot Jupiters". Later that year, they confirmed Latham's discovery as a planet.
It was clear we had ignored a fundamental rule of science. "We had been judging the cosmic diversity of planetary systems based on a sample size of one," says Marcy."
and there's more!
"If these were the first hints that our solar system was not normal, they were not the last. Other planets were soon caught breaking all sorts of rules: orbiting in the opposite direction to their star's spin, coming packed in close orbits like sardines in a can, or revolving on wildly tilted orbits far away from their star's equator"
"All this makes the status of our solar system increasingly clear. "Our system is a rarity, there's no longer a question about that," says Marcy. "The only question that remains is, just how rare is it?""
Rest of the article http://www.newscientist.com/article/mg21028122.700-no-place-like-home-our-lonesome-solar-system.html? (http://www.newscientist.com/article/mg21028122.700-no-place-like-home-our-lonesome-solar-system.html?) but you'll have to register to read it in full.
Goodness me, what a pleasant surprise to the usual dross of 'we havent search long \ hard \ far enough' of the galaxy yet. But, in a topic some people want to use 'sampling' to both support their argument and knock other down when it suits, it is a valid question. Not only that, but the evidence is imo, pointing towards uniqueness.
-
Well sorry not to have posted in here for a little while but I thought I'd let someone take a rest :}
We're all very thankful for that....
"All this makes the status of our solar system increasingly clear. "Our system is a rarity, there's no longer a question about that," says Marcy. "The only question that remains is, just how rare is it?""
Rest of the article http://www.newscientist.com/article/mg21028122.700-no-place-like-home-our-lonesome-solar-system.html? (http://www.newscientist.com/article/mg21028122.700-no-place-like-home-our-lonesome-solar-system.html?) but you'll have to register to read it in full.
Goodness me, what a pleasant surprise to the usual dross of 'we havent search long \ hard \ far enough' of the galaxy yet. But, in a topic some people want to use 'sampling' to both support their argument and knock other down when it suits, it is a valid question. Not only that, but the evidence is imo, pointing towards uniqueness.
Your original argument was that the Solar System was rare or unique - in particular that Earth-like planets (essentially small, rocky, with liquid water and an atmosphere) would be very rare and hence there was unlikely to be much (or any) possibility of extra-terrestrial life.
The article you cite certainly includes the words 'our system is a rarity', but goes on to make the following point:
"The diversity of these planetary systems tells us that our own is but one example in a very wide range," says Andrew Howard, a planet-hunter at the University of California, Berkeley. But it is not quite time to give up on another solar system that looks like ours, he adds. For Kepler to "find" a planet, that planet must transit across its star three times. Given a planned mission lifetime of three and a half years, Earth would have made the cut - just. But it would take 36 years for Jupiter to make the grade, 90 for Saturn, and even longer for Uranus and Neptune. "If we were looking from outside we still wouldn't have detected most of our solar system," says Howard.
The search for a second Earth
While astronomers seek a planetary system that mimics the architecture of our own, the number of Earth-like worlds is another open question.
In October last year, Andrew Howard and Geoff Marcy of the University of California, Berkeley, released a census of planets orbiting within a quarter of the Earth-sun distance of 150 nearby sun-like stars. A few per cent have close-in planets Jupiter's size or greater, about twice as many have Neptune-mass planets, and at least 12 per cent harbour planets three times Earth's mass, the smallest in the sample. This trend would suggest that one in four sun-like stars have close-in planets Earth's size (Science, vol 330, p 653).
"It tells us that nature makes small planets," says Howard. And while life as we know it would be burned out on these planets, if there are that many planets close in, there are presumably quite a few further out at Earth-like distances.
So it is not the case that the vast majority of all the other systems are definitely 'dead' and ours is likely to be the only one with life. The article makes the point that there is a very wide range of system types (which we didn't expect) and many of them may be capable of supporting life. The Solar System is only 'rare' in the sense that there appear to be many different possible system configurations, of which ours is only one. And the article also points out that the 'sampling' issue is a real and valid reason why "the number of Earth-like worlds is another open question.".
Not only that, but the article also says: "... But it is not quite time to give up on another solar system that looks like ours, he adds. For Kepler to "find" a planet, that planet must transit across its star three times. Given a planned mission lifetime of three and a half years, Earth would have made the cut - just. But it would take 36 years for Jupiter to make the grade..." That seems to me to be a classic example of "the usual dross of 'we havent search long \ hard \ far enough' of the galaxy yet.", which you seem to think is absent from this paper. I find that when I read your cites they frequently contain statements which say the opposite of what you are suggesting. Don't you read right down to the bottom of them?
-
I seem to remember some earlier discussion about tidally-locked planets in the Gleise system, and an assertion made that tidal locking would create extreme variations of climate which would suppress the development of life....
This piece of work may be interesting in that context: http://www2.cnrs.fr/en/1862.htm
It reports a physical model of the expected features of tidally-locked Gleise 581D, which shows "that with a dense carbon dioxide atmosphere - a likely scenario on such a large planet - the climate of Gliese 581d is not only stable against collapse, but warm enough to have oceans, clouds and rainfall.."
The planet is considerably bigger that the Earth, and gets only about 1/7 the sunlight that Earth does, so it would not normally be considered as an Earth-type candidate. But the model suggests that Earth-like temperatures and humidity may still be available. So you do NOT necessarily need an Earth-type planet to harbour Earth-like life conditions. As the conclusion says:
"But the diversity of planetary climates in the galaxy is likely to be far wider than the few examples we are used to from the Solar System. In the long run, the most important implication of these results may be the idea that life-supporting planets do not in fact need to be particularly like the Earth at all. "
So a 'unique Earth' does not necessarily mean a lifeless Galaxy. We are beginning to learn that there are many possibilities out there...
-
Yes and I seem to remember earlier discussions saying its just a question of time in proving our solar system was the norm. Now, some astronomers are starting to realise that may not be the case.
Pretty much a theoretical paper about Gliese, that one. So, in theory yes, it could be. Likelihood of it being the case, improbable.
-
... I seem to remember earlier discussions saying its just a question of time in proving our solar system was the norm. Now, some astronomers are starting to realise that may not be the case...
Looked - couldn't find anywhere that was said. The nearest I could get was this:
Reply 10
The paper you have cited is in agreement with Mandell, Raymond and Sigurdsson (2007) ( http://iopscience.iop.org/0004-637X/660/1/823/70644.text.html ) which says:
"If planetary systems that suffer the migration of a gas giant to small distances can eventually form terrestrial planets similar to those in our own system, and the migration of young giant planets is a common result of interactions with the gaseous disk, then it is appropriate to consider the possibility that our own planetary system could have formed earlier generations of giant planets prior to those in the outer solar system.
It is early days yet, as I have often said, but it looks to me as if the migrating hot jupiter theory provides a good explanation of how inner habitable planets can be formed, and may well be the norm for our kind of system....
and I am happy to stand by that suggestion.
We have sent up a probe intended to find planets orbiting nearby stars which are similar to our own. We always knew that we would detect the planets with short orbits first, and we have not yet had the time to detect planets as far out as ours is, so none of the findings will be exactly Earth-like.
What has surprised us is that quite a lot of systems have large planets close to their suns - these seem to have migrated inwards. After a period of consideration, it now seems plausible that this is a common stage in planetary development, and may indeed have happened to our own system in the distant past, as suggested in the paper referenced above. So the systems we have found so far may be well be similar to ours, but at a different stage of development....
We have also found other systems which could have Earth-like planets in them orbiting suns which are not Sun-like. I don't think that anyone has claimed that the Solar System is 'the norm' for systems in the galaxy - for one thing 90% of the stars in the Milky Way are dwarf stars smaller than ours, but the aim of the Kepler probe was to advance our knowledge about Earth-like planets, and it seems to be finding likely candidates quite rapidly, suggesting that there may be quite a few out there...
-
Now the corot missions finds 10 new planets.
But "the latest list of 10 exoplanet finds, seven are so-called "hot Jupiters", gas giant planets similar to our own Jupiter but far closer to their host star - completing their orbits in just days.
Two more orbit the star Corot-24, with diameters equal to and about 1.4 times that of Neptune, completing their orbits in five and 12 days, respectively."
Yet more evidence that our solar system is tending to uniqueness. >>:-(
oops! Forgot the linky!
http://www.bbc.co.uk/news/science-environment-13761405 (http://www.bbc.co.uk/news/science-environment-13761405)
-
But "the latest list of 10 exoplanet finds, seven are so-called "hot Jupiters", gas giant planets similar to our own Jupiter but far closer to their host star - completing their orbits in just days.
Yet more evidence that our solar system is tending to uniqueness. >>:-(
Yaaawn! How many times do we have to tell you that these probes will ALWAYS find the large close planets FIRST? The fact that they are finding them proves nothing about other systems which may be similar to ours, and so do not have large planets close to their sun, which will therefore not be so easily detected.
Incidentally, we only seem to hear from you when the mass media put out a story. There is a lot of extra-solar planetary work going on at the moment, much of it tending to show that non-terrestrial life is quite likely to be found. And yet we do not hear anything from you about this. You seem to be only choosing papers which fit your (mistaken) world view.
For example, take the classic belief that having a large close-coupled Moon is essential for the development of life on this planet. It tends to protect us from meteorite bombardment, and gives us the tides, which are often seen as critically important in bio-development. It also holds us level in the axial plane and minimises gravitational disturbance from other planets. The Earth-Moon system is almost a double planet, and the only other comparable pair in the Solar System is Pluto/Charon, so getting one in the habitable zone was thought to be quite rare, and often cited by rare-earth enthusiasts as another reason for believing that our system 'tended to uniqueness', and was the only one where life had developed as a result.
Here are two papers released over the last month, both addressing the 'rare moon' issue. One suggests that 'double-planet' moon systems may actually be ten times as common as was thought, while the other suggests that it may not matter anyway, as the stability influence that a big Moon provides is less important than was thought.
http://www.slideshare.net/sacani/how-common-are-earth-moon-planetary-systems
http://news.sciencemag.org/sciencenow/2011/05/who-needs-a-moon.html?ref=hp
If I wanted to it would be easy to inundate this thread with examples of research tending to show that Earth-like systems are likely to be quite common in the Galaxy, and that the conditions for life that we would recognise are likely to occur on many of these, as well as many other system which are not like ours, but could still harbour life. I can't see why I should, particularly on a model boat board....