Earth is likely the only planet with life: Princeton scientists

[Rathma]

https://www.eutimes.net/2012/04/us-scientists-say-earth-may-be-the-only-planet-with-life/

NASA has said there are ‘billions’ of planets in our own Milky Way galaxy – but a new study suggests that the idea that they are teeming with alien lifeforms may just be wishful thinking.
Two Princeton scientists used what’s known as ‘Bayesian analysis’ – a technque that ‘boils down’ ideas to the actual data, as opposed to scientists’ own ideas about what ‘should’ be true.
They suggest that it’s very possible Earth is a one-off aberration where life took hold unusually fast – and on the average extraterrestrial planet, the chances of life are very low indeed.
‘Fossil evidence suggests that life began very early in Earth’s history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn’t reveal much about the actual probability of life on other planets,’ said Princeton astrophysical sciences professor Edwin Turner and David Spiegel, a former Princeton postdoctoral researcher.
‘Information about that probability comes largely from the assumptions scientists have going in, and some of the most optimistic conclusions have been based almost entirely on those assumptions,’ he said.
‘If scientists start out assuming that the chances of life existing on another planet as it does on Earth are large, then their results will be presented in a way that supports that likelihood,’ Turner said.
‘Our work is not a judgment, but an analysis of existing data that suggests the debate about the existence of life on other planets is framed largely by the prior assumptions of the participants.’
Joshua Winn, an associate professor of physics at the Massachusetts Institute of Technology, said that Turner and Spiegel cast convincing doubt on the basis for expecting extraterrestrial life.
Winn, who focuses his research on the properties of exoplanets, is familiar with the research but had no role in it.
‘There is a commonly heard argument that life must be common or else it would not have arisen so quickly after the surface of the Earth cooled,’ Winn said.
‘This argument seems persuasive on its face, but Spiegel and Turner have shown it doesn’t stand up to a rigorous statistical examination — with a sample of only one life-bearing planet, one cannot even get a ballpark estimate of the abundance of life in the universe.
rgence of life on Earth gave reasons to be optimistic about the search for life elsewhere,’ Winn said. ‘Now I’m not so sure, though I think scientists should still search for life on other planets to the extent we can.’
Deep-space satellites and telescope projects have recently identified various planets that resemble Earth in their size and composition, and are within their star’s habitable zone, the optimal distance for having liquid water.
Of particular excitement have been the discoveries of NASA’s Kepler Space Telescope, a satellite built to find Earth-like planets around other stars.
While these observations tend to stoke the expectation of finding Earth-like life, they do not actually provide evidence that it does or does not exist, Spiegel explained. Instead, these planets have our knowledge of life on Earth projected onto them, he said.
Yet, when what is known about life on Earth is taken away, there is no accurate sense of how probable abiogenesis is on any given planet, Spiegel said. It was this ‘prior ignorance,’ or lack of expectations, that he and Turner wanted to account for in their analysis, he said.
‘When we use a mathematical prior that truly represents prior ignorance, the data of early life on Earth becomes ambiguous,’ Spiegel said.
Spiegel and Turner also propose that once this planet’s history is considered, the emergence of life on Earth might be so distinct that it is a poor barometer of how it occurred elsewhere, regardless of the likelihood that such life exists.

I never completely bought into the alien thing. Yes it kind of makes sense as the next logical step in refuting the old idea that the universe revolves around us humans. It seems like if there is life on this planet then there should be life on the gazillions of other planets. People say that you would be arrogant to think that the Earth is somehow special. But the bottom line is we don't have the information to address this question scientifically yet. In my personal opinion, I think there is a lot of weird shit happening on other planets, but nothing is probably similar at all to life on Earth.

Anyways, those people bitching about their giant alien satellites being underfunded will not like this.

[El Barto]

So in other words, we don't know anything and should take nothing for granted.  Yeah, cool. I'll buy that.

[ResultsMayVary]

These guys are right, but the likelihood of us being alone is so small. The universe is just too big (so big we can't even imagine it). I hope that scientists find something soon so we can end this debate. Too bad that definition of soon could be in a hundred or thousand years or whenever more technological advances allow us to travel to other solar systems.

[Chino]

Princeton needs to fire this guy like yesterday.

[Chino]

These guys are right, but the likelihood of us being alone is so small. The universe is just too big (so big we can't even imagine it). I hope that scientists find something soon so we can end this debate. Too bad that definition of soon could be in a hundred or thousand years or whenever more technological advances allow us to travel to other solar systems.

I'd still be amazed if it didn't exist elsewhere in our own solar system.

[Omega]

Here's actually a very interesting video on the circumstances necessary for the formation of life. It's a little long, but its worth watching, if you find the time.

https://www.youtube.com/watch?v=Htfl2rXFezo&feature=g-u-u&context=G2b1a7dbFUAAAAAAAJAA

[Rathma]

Asking whether or not there is life on other planets is kind of like asking whether or not there is a god.

Both lead to unproductive debates that go on and on without defining the most important terms.

And that's what's going to happen in this thread. So lol.

[Progmetty]

Well we can't find them and they can't find us. And until that changes we need to give it a rest cause I really think humanity has over-killed that discussion.

[Scheavo]

Asking whether or not there is life on other planets is kind of like asking whether or not there is a god.

Not really.

We can reasonably assume there is other life out there, based upon what we know about physics, and chemistry. Many amino acids are determined to exist due to thermodynamics. Every other aspect of life is simply a chemical reaction, and it would really require an explanation at this point as to why Earth is unique, or at least why conditions are so unhospitable elsewhere.

But yes, we do need a proper definition of life. Complex and intelligent life like ourselves is probably rarer still, but there's trillions of possibilities in the universe.

Meanwhile, we have found planets in the universe that are in the green zone, and terrestrial.

[lordxizor]

I do think it's likely that life in some form exists elsewhere, but they make a good point. We really don't know that much about the universe and the make-up of other planets. We make the assumption that Earth is not unique and if life can form here, it can form elsewhere. But really, we have no idea how unique Earth is. We observe Earth-like planets, but don't really know a whole lot about them. It may be that Earth had just the right mix of ingredients and if it's off slightly, life couldn't form.

This is very true:

Fossil evidence suggests that life began very early in Earth’s history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn’t reveal much about the actual probability of life on other planets

We assume life must exist elsewhere mostly based on a gut feeling and the fact that there's a ton of stars in the universe. But we really know next to nothing about how life can form. People throw out "If one in a million stars have planets and one in a million of them can support life, there must be lmillions of lifeforms out there." That one in a million number is a complete guess. It could be one in 100 or 1 in 10^200. Without statistics on how many planets there ae an how many have life, it's basically just complete speculation and gut feelings.

[Super Dude]

I'm sure life is out there somewhere, but I'm also sure the universe isn't *teeming* with life. I'm also sure that if it is out there somwhere, even if we do come into contact, we will never meet face-to-face. The universe is too damn big for such a double coincidence.

[Scheavo]

I do think it's likely that life in some form exists elsewhere, but they make a good point. We really don't know that much about the universe and the make-up of other planets. We make the assumption that Earth is not unique and if life can form here, it can form elsewhere. But really, we have no idea how unique Earth is. We observe Earth-like planets, but don't really know a whole lot about them. It may be that Earth had just the right mix of ingredients and if it's off slightly, life couldn't form.

This is very true:

Fossil evidence suggests that life began very early in Earth’s history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn’t reveal much about the actual probability of life on other planets

We assume life must exist elsewhere mostly based on a gut feeling and the fact that there's a ton of stars in the universe. But we really know next to nothing about how life can form. People throw out "If one in a million stars have planets and one in a million of them can support life, there must be lmillions of lifeforms out there." That one in a million number is a complete guess. It could be one in 100 or 1 in 10^200. Without statistics on how many planets there ae an how many have life, it's basically just complete speculation and gut feelings.

Then it's completely speculation and gut feeling to imagine that the stars we view hold to the same physical laws as our own.

I'm sure life is out there somewhere, but I'm also sure the universe isn't *teeming* with life. I'm also sure that if it is out there somewhere, even if we do come into contact, we will never meet face-to-face. The universe is too damn big for such a double coincidence.

When you say big, are you implying time differences as well?

[rumborak]

Regarding the OP, I don't see how, given the utter lack of data, anything more than speculation can be done. It's not a question of whether you like Bayesian statistics or not; it's a question of whether you're an optimist or not.

rumborak

[Super Dude]

I do think it's likely that life in some form exists elsewhere, but they make a good point. We really don't know that much about the universe and the make-up of other planets. We make the assumption that Earth is not unique and if life can form here, it can form elsewhere. But really, we have no idea how unique Earth is. We observe Earth-like planets, but don't really know a whole lot about them. It may be that Earth had just the right mix of ingredients and if it's off slightly, life couldn't form.

This is very true:

Fossil evidence suggests that life began very early in Earth’s history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn’t reveal much about the actual probability of life on other planets

We assume life must exist elsewhere mostly based on a gut feeling and the fact that there's a ton of stars in the universe. But we really know next to nothing about how life can form. People throw out "If one in a million stars have planets and one in a million of them can support life, there must be lmillions of lifeforms out there." That one in a million number is a complete guess. It could be one in 100 or 1 in 10^200. Without statistics on how many planets there ae an how many have life, it's basically just complete speculation and gut feelings.

Then it's completely speculation and gut feeling to imagine that the stars we view hold to the same physical laws as our own.

I'm sure life is out there somewhere, but I'm also sure the universe isn't *teeming* with life. I'm also sure that if it is out there somewhere, even if we do come into contact, we will never meet face-to-face. The universe is too damn big for such a double coincidence.

When you say big, are you implying time differences as well?

That hadnt occurred to me, but it makes sense.

[jammindude]

Isn't the concept believing in alien life exactly the same as believing in the concept of believing in God?   In that, we have no proof but we want to believe it so badly that we make it true?  "It must be...therefore it *HAS* to be...because the opposite is such a high mathematical improbability, that the alternative MUST be fact."

[lordxizor]

I do think it's likely that life in some form exists elsewhere, but they make a good point. We really don't know that much about the universe and the make-up of other planets. We make the assumption that Earth is not unique and if life can form here, it can form elsewhere. But really, we have no idea how unique Earth is. We observe Earth-like planets, but don't really know a whole lot about them. It may be that Earth had just the right mix of ingredients and if it's off slightly, life couldn't form.

This is very true:

Fossil evidence suggests that life began very early in Earth’s history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn’t reveal much about the actual probability of life on other planets

We assume life must exist elsewhere mostly based on a gut feeling and the fact that there's a ton of stars in the universe. But we really know next to nothing about how life can form. People throw out "If one in a million stars have planets and one in a million of them can support life, there must be lmillions of lifeforms out there." That one in a million number is a complete guess. It could be one in 100 or 1 in 10^200. Without statistics on how many planets there ae an how many have life, it's basically just complete speculation and gut feelings.

Then it's completely speculation and gut feeling to imagine that the stars we view hold to the same physical laws as our own.

It has nothing to do with physical laws. It may be that a very specific temperature range, mix of elements, sunlight, barometric pressure, lightning bolt at the exact right moment, etc may be necessary for life. It may be that the required recipe is so incredibly rare and unlikely to occur that no other life exists. Holding either viewpoint is really just speculation since we don't know.

[Super Dude]

Isn't the concept believing in alien life exactly the same as believing in the concept of believing in God?   In that, we have no proof but we want to believe it so badly that we make it true?  "It must be...therefore it *HAS* to be...because the opposite is such a high mathematical improbability, that the alternative MUST be fact."

Not really, no. It will eventually be possible (not soon but eventually) to empirically prove the existence or non-existence of alien life and then answer the question definitively. The existence of God will never be provable by scientific inquiry. Hence faith.

[jammindude]

Isn't the concept believing in alien life exactly the same as believing in the concept of believing in God?   In that, we have no proof but we want to believe it so badly that we make it true?  "It must be...therefore it *HAS* to be...because the opposite is such a high mathematical improbability, that the alternative MUST be fact."

Not really, no. It will eventually be possible (not soon but eventually) to empirically prove the existence or non-existence of alien life and then answer the question definitively. The existence of God will never be provable by scientific inquiry. Hence faith.

Unless God were to take some action...that would be empirical.    (I understand that I believe and not everyone does...so in that sense I'm speaking theoretically for the sake of argument)

[El Barto]

Isn't the concept believing in alien life exactly the same as believing in the concept of believing in God?   In that, we have no proof but we want to believe it so badly that we make it true?  "It must be...therefore it *HAS* to be...because the opposite is such a high mathematical improbability, that the alternative MUST be fact."

We know for a fact that life exists already.  Despite the small sample size (one), we can still reasonably assume that life elsewhere is a possibility.  We have no such frame of reference with God.  He's starting from ground zero, so to speak. 

[Scheavo]

It has nothing to do with physical laws. It may be that a very specific temperature range, mix of elements, sunlight, barometric pressure, lightning bolt at the exact right moment, etc may be necessary for life. It may be that the required recipe is so incredibly rare and unlikely to occur that no other life exists. Holding either viewpoint is really just speculation since we don't know.

Actually, it does. If organic chemicals and other chemicals necessary for life are thermodynamically determined to come about, that means the chemicals necessary for life are everywhere.

Thing is, we've already found so many planets that are found in the "goldilocks" zone - which is itself assuming life has to be exactly like us, which is false and not very true of life on earth - that really, the numbers game is so far in favor of there being life, at least some form of life, somewhere. To say anything else requires that we assume the physical laws, especially thermodynamics, are not universal. They well could be, by the way. I'm simply saying that, given what we know if physics and chemistry, it is logical and straightforward to assume life exists elsewhere in the universe.

Cause here's the thing, there is literally so much in the universe, that the odds of anything occurring is pretty much guaranteed. Something with .0000001% chance of occurring, is almost certain to occur in the universe. So even if life is extremely rare, trillions and trillions of chances means there will be more than 1.

The numbers are simply too large. Like I mentioned earlier, finding a star with the exact same mass as our Suns is pretty damn extraordinary. The fact that it's only 200 light years away makes it even more extraordinary.

https://news.discovery.com/space/suns-twin-is-an-optimum-seti-target-120426.html

Forgot it even has the same chemical composition.

Isn't the concept believing in alien life exactly the same as believing in the concept of believing in God?   In that, we have no proof but we want to believe it so badly that we make it true?  "It must be...therefore it *HAS* to be...because the opposite is such a high mathematical improbability, that the alternative MUST be fact."

Not really, no. It will eventually be possible (not soon but eventually) to empirically prove the existence or non-existence of alien life and then answer the question definitively. The existence of God will never be provable by scientific inquiry. Hence faith.

Unless God were to take some action...that would be empirical.    (I understand that I believe and not everyone does...so in that sense I'm speaking theoretically for the sake of argument)

No, becuase when we talk about life existing elsewhere, we use empirical knowledge and what we know about here, and out there. There is no real appeal to ignorance, like there would be in discussing the "proof" of God. Saying that life exists elsewhere is a result of empirical data on how much stars there are, empirical data on chemistry and physics, and empirical data on what life is on our planet, and what it does.

[lordxizor]

Cause here's the thing, there is literally so much in the universe, that the odds of anything occurring is pretty much guaranteed. Something with .0000001% chance of occurring, is almost certain to occur in the universe. So even if life is extremely rare, trillions and trillions of chances means there will be more than 1.

You're kind of missing the point of the article I think. They're saying that we don't have the slightest clue what the liklihood of life is. You throw out 0.0000001% chance showing that over trillions of stars, life becomes likely. What if it's a 0.0000000000000000000000000000000000000000000000001% chance? Not so lilkely anymore. We simply don't have enough data to know. Just because some of the basic building blocks of life are fairly easy to produce doesn't mean life is likely to form. I like you tend to believe it's more likely than not, but that's really based on no real information, but more just an opinion.

[Scheavo]

Cause here's the thing, there is literally so much in the universe, that the odds of anything occurring is pretty much guaranteed. Something with .0000001% chance of occurring, is almost certain to occur in the universe. So even if life is extremely rare, trillions and trillions of chances means there will be more than 1.

You're kind of missing the point of the article I think. They're saying that we don't have the slightest clue what the liklihood of life is. You throw out 0.0000001% chance showing that over trillions of stars, life becomes likely. What if it's a 0.0000000000000000000000000000000000000000000000001% chance? Not so lilkely anymore. We simply don't have enough data to know. Just because some of the basic building blocks of life are fairly easy to produce doesn't mean life is likely to form. I like you tend to believe it's more likely than not, but that's really based on no real information, but more just an opinion.

Well, let me put this way, given what we know, life is probable to exist in other parts of the universe. This paper, saying that Earth is likely on the planet with life, flies in the face of everything we know. Is it possible? Ya But you really start begging soooooooOOOo many questions, that the only justifiable position is that there is life somewhere. It doesn't mean there's intelligent life, especially not at this given period of time in the Universes history, it just means that there's at least bacteria floating around out there.

All of this ignores one of the stronger theories for how long came to be in this planet, which involves comets, asteroids and other debris bringing some of the vital components that got things going.

*edit*
And as long as we're playing the "what if" game, what if the probability of life coming about is not rare, but quite common? Even .1 would mean it's everywhere. The thing is, we don't know that number, so to say that it's likely that is the only place is fallacious. My argument for why life probably exists somewhere else in the universe doesn't hinge upon what this number is, it hinges upon what we see and know to be true around us. All of the conditions necessary for life are not uncommon in the Universe, so even if it takes chance within these necessary conditions(lightning strike at right time?, etc), that still makes life rather probable.

[Dublagent66]

Life elsewhere is a mathematical certainty.  It's only a matter of time.

[ResultsMayVary]

These guys are right, but the likelihood of us being alone is so small. The universe is just too big (so big we can't even imagine it). I hope that scientists find something soon so we can end this debate. Too bad that definition of soon could be in a hundred or thousand years or whenever more technological advances allow us to travel to other solar systems.

I'd still be amazed if it didn't exist elsewhere in our own solar system.

I'd honestly be surprised if Europa didn't have some form of life on it. That seems like the only place in the solar system that I can see life developing (from something carbon-based and water-needing). I think we'll eventually find other organisms out there that have different structures and are based from different elements. I think it may be an appropriate saying that we may be the only planet that's mostly carbon-based and full of organisms that require water to survive. I think that's a more reasonable determination at this time.

Life elsewhere is a mathematical certainty.  It's only a matter of time.

Pretty much this.

[kári]

These guys are right, but the likelihood of us being alone is so small. The universe is just too big (so big we can't even imagine it). I hope that scientists find something soon so we can end this debate. Too bad that definition of soon could be in a hundred or thousand years or whenever more technological advances allow us to travel to other solar systems.

I'd still be amazed if it didn't exist elsewhere in our own solar system.

I think it may be an appropriate saying that we may be the only planet that's mostly carbon-based and full of organisms that require water to survive. I think that's a more reasonable determination at this time.

I'm sorry but that statement (though very widely believed) is just very, very ill-informed. Carbon is the sixth most abundant element in universe. There are very few if none molecules with more than say 10 atoms that don't contain carbon. Any other life out there has pretty much a 100% probability of being carbon-based. I think I made a post about this a few months ago, let me find it.

EDIT:

Pretty much all astronomers agree that if there is extraterrestial life, it will most likely also be carbon based.
https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements

Look at the table on the right "Ten most common elements in the Milky Way Galaxy estimated spectroscopically[1]". By extrapolation, this is also valid for the rest of the universe today. As you can see, there's just a LOT of carbon. That's one reason.
Another reason is carbon can bond to 4 other atoms, a property not many other elements posses. The next element in the list that has 4 valence electrons is Silicon but it's by good approximation 10x rarer than carbon. Which makes a lot harder than 10 times for two Silicon atoms to bond than for two carbon atoms.

Both of those arguments translate itself into the fact that if you look at the molecules with more than 2 atoms that we have detected so far, pretty much all of them contain carbon (the only one containing silicon and not carbon is SiH4 from a quick glance at the article below).
Take a look at this: https://en.wikipedia.org/wiki/List_of_molecules_in_interstellar_space and tell me that extra-terrestial life, if it exists, will not be carbon-based.

[kirksnosehair]

Life elsewhere is a mathematical certainty.  It's only a matter of time.

Well played?