# Basis of science's belief that extraterrestrial life is likely? **URL:** \ **Category:** Great Debates\ **Created:** [November 10, 2010, 3:43am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137 "2010-11-10T03:43:11Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [November 10, 2010, 5:28am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/21 "2010-11-10T05:28:32Z")
> [@Diogenes\_the\_Cynic](#): > > By the way, we do have that Mars rock which appear to have fossilized, nanobacterial lifeforms on it (a hypothesis which still has not been refuted nor has any better hypothesis been offered). That’s abiogenesis twice in one solar system. That’s not how science works. One doesn’t put forth a hypothesis and assume it stands unless someone refutes it. Hypotheses have to be proven. This one has not been. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [November 10, 2010, 5:29am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/22 "2010-11-10T05:29:59Z")
> [@John\_Mace](#): > > What happened on Earth is possible on any Earth-like planet Make that “sufficiently Earth-like” - with the problem being that we don’t - perhaps can’t - know what’s sufficient. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [November 10, 2010, 5:30am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/23 "2010-11-10T05:30:59Z")
> [@John\_Mace](#): > > Unless we assume that the laws of physics are different depending on where you are in the universe, then Earth is no unique place. What happened on Earth is possible on any Earth-like planet, of which there must be billions. In fact, we don’t even know that life on Earth originated on Earth. All true. > [@](#): > > Knowing what we know, life should exist elsewhere. To assume otherwise, we have to assume knowledge that we don’t have. At which point your post becomes a non-sequitur. What are these things we know that allow you to conclude that life should exist elsewhere? As I noted in the OP, the Earth could be perfectly ordinary in every way except the presence of life, and still be the only planet in the universe with life. The man who got killed by a meteorite was ordinary in every way. Just like tens of millions of others, except that he got struck by a meteorite. That doesn’t allow us to conclude that meteorite mortalities should exist everywhere does it? In fact his ordinariness doesn’t allow us to conclude much at all about meteorite fatalities as far as I can see. ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [November 10, 2010, 5:31am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/24 "2010-11-10T05:31:30Z")
> [@John\_Mace](#): > > That’s not how science works. One doesn’t put forth a hypothesis and assume it stands unless someone refutes it. Hypothesis have to be proven. This one has not been. It’s the BEST hypothesis, and nothing else really makes sense. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [November 10, 2010, 5:32am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/25 "2010-11-10T05:32:45Z")
> [@Diogenes\_the\_Cynic](#): > > It’s the BEST hypothesis, and nothing else really makes sense. Cite? ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [November 10, 2010, 5:33am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/26 "2010-11-10T05:33:57Z")
The universe is really big and there is nothing special about the conditions on earth. If earth-like conditions are ubiquitous in the universe (which they are), then it is necessary to show that something would prevent the same processes from occuring on those rocks which occurred on this one. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [November 10, 2010, 5:33am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/27 "2010-11-10T05:33:58Z")
The argument in the OP would be very plausible - if we knew absolutely nothing about the structure of life. Since we do, not so much. First, if any scientist claims that life exists elsewhere, he or she would be going far beyond the available evidence. The actual claim, which is in the title of the OP, is that it is likely. I point this out to warn against carelessness in confusing claims of existence and claims of likelihood. It is not true that we have no idea of how life arose on earth. We in fact have lots of ideas - knowing which one is right, if any, is another matter. Not surprising since we are looking for evidence of tiny molecules existing a billion years ago or so. We’ve gone considerably beyond the Urey experiment. We can construct a virus in the lab - not quite living, but close. We certainly do know how it is put together. I like the spontaneous creation of a self-replicating but non-living molecule myself, which would then “evolve” (descent with modification) into DNA over time. We know self-replicating molecules exist, and I’m pretty certain RNA is not the least complex of these, so it seems plausible. Asserting that the probability of life arising is incredibly low is as absurd as claiming without evidence that the probability is unity. Meanwhile, we seem to have evidence that the number of planets around exceeds the most optimistic predictions I read as a kid. So, that is more evidence that life is likely. So, I’ve given a semi-plausible argument for the likeliness of life. Is there an argument against, except from incredulity? ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [November 10, 2010, 5:35am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/28 "2010-11-10T05:35:02Z")
> [@John\_Mace](#): > > Cite? [Read the wiki](http://en.wikipedia.org/wiki/Allan_Hills_84001). ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [November 10, 2010, 5:35am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/29 "2010-11-10T05:35:55Z")
> [@Chronos](#): > > What part of “infinite” are you not understanding? Nothing as far as I can tell. If you think I am making a mistake then please explain. If the universe is infinite, yet the probability of life arising is equal to the entire number of particles in that universe, then how probable is it that life arises? > [@](#): > > And your argument about “life had to evolve fast or not at all” still doesn’t make any sense, especially since the asteroid impacts and such that you claim would endanger proto-life are much rarer now than they were when life actually did evolve. If life had to get past those first hurdles before the next asteroid impact, then we would expect to see that life on our planet only arose in the past billion years or so, not that it had been present basically from the beginning. No, that is totally illogical. 1. Asteroid impacts are one factor that may have declined. The passage through oceanic vents that Miller (of Urey-Miller fame) posited as the reason why life need to arise fast, are still sterilising the entire ocean every few million years. Various other catastrophes may or may not be getting more frequent. 2. It required 4 billion years for intelligent life to evolve. If life on our planet only arose in the past billion years or so then, by definition, we wouldn’t be there to see it. ---
**Author:** ![silk1976](https://avatars.discourse-cdn.com/v4/letter/s/8edcca/32.png) [@silk1976](https://boards.straightdope.com/u/silk1976)\ **Post date:** [November 10, 2010, 5:36am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/30 "2010-11-10T05:36:03Z")
Based on the OP of the original thread, asking what the basis of science’s belief that ET is likely - everything I have heard on the subject from prominent physicists and such (Hawking, Tyson) indicate that they simply believe it exists because: 1. the universe is a very, very large place 2. there is nothing inherently super-special about earth. Physics and chemistry are not different here as compared to the rest of the universe. Earth is special only because of the rather exceptional, based on what we’ve seen of other planets, turn of events to allow life to thrive here. Hence, based on simple probability - it is a good bet that there is life elsewhere. That is not to say it is guaranteed, or that the chance is closer to 100% than say, 60% - it is just saying that if you had to wager a bet, evidence gathered in the scientific community suggests that you are more likely to win betting on life being elsewhere in the universe. Intelligent life could be another story. I’d personally put my money on it, but that is a whole other debate. I really don’t see why this topic has warranted this much debate, other than it getting sidetracked by minutae such as how life formed, specific chances, etc. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [November 10, 2010, 5:37am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/31 "2010-11-10T05:37:42Z")
> [@Diogenes\_the\_Cynic](#): > > Intelligence is neither here nor there. The question is only about life, not intelligent life. Absolute nonsense, as usual. If intelligent life had not arisen on this planet then how could we be discussing conditions on this planet. > [@](#): > > There is nothing special about the conditions on earth that led to replicating RNA molecules. Cite. > [@](#): > > By the way, we do have that Mars rock which appear to have fossilized, nanobacterial lifeforms on it (a hypothesis which still has not been refuted nor has any better hypothesis been offered). Cite! > [@](#): > > That’s abiogenesis twice in one solar system. Cite. ---
**Author:** ![AdmiralCrunch](https://avatars.discourse-cdn.com/v4/letter/a/6f9a4e/32.png) [@AdmiralCrunch](https://boards.straightdope.com/u/AdmiralCrunch)\ **Post date:** [November 10, 2010, 5:37am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/32 "2010-11-10T05:37:51Z")
Who’s representing “science”, and what is the basis for your belief that science believes that extraterrestrial life is likely? Sure, you may find exuberant cosmologists casually opining about the splendor of the universe, but that’s not science. To answer the spirit of your question, though, I’d suggest the [Copernican principle](http://en.wikipedia.org/wiki/Copernican_principle). That seems to be the basis of scientists’ beliefs in the non-rarity of earth. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [November 10, 2010, 5:38am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/33 "2010-11-10T05:38:09Z")
> [@Blake](#): > > What are these things we know that allow you to conclude that life should exist elsewhere? As I noted in the OP, the Earth could be perfectly ordinary in every way except the presence of life, and still be the only planet in the universe with life. It could be, but why would it be? > [@](#): > > The man who got killed by a meteorite was ordinary in every way. Just like tens of millions of others, except that he got struck by a meteorite. That doesn’t allow us to conclude that meteorite mortalities should exist everywhere does it? Yes, it does, provided a large enough sample size. > [@](#): > > In fact his ordinariness doesn’t allow us to conclude much at all about meteorite fatalities as far as I can see. Except that his ordinariness is only one part of the equation. The other part being the frequency of meteorite strikes. ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [November 10, 2010, 5:39am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/34 "2010-11-10T05:39:36Z")
> [@Blake](#): > > Absolute nonsense, as usual. > > If intelligent life had not arisen on this planet then how could we be discussing conditions on this planet. We couldn’t be. So what? What the fuck does that have to do with the possibility of microbes existing elsewhere in the universe? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [November 10, 2010, 5:41am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/35 "2010-11-10T05:41:32Z")
> [@Diogenes\_the\_Cynic](#): > > The universe is really big and there is nothing special about the conditions on earth. If earth-like conditions are ubiquitous in the universe (which they are), then it is necessary to show that something would prevent the same processes from occuring on those rocks which occurred on this one. Not this nonsense again. Why Dio? Why is this necessary? Even if the probability oflife arsing on any planet is the low one,nothing in this contention requires Earth to be special. Let’s assume hypothetically that the probability on any given planet is 1/10^87. That is the probability on all planets, 0n any planet. On any given planet. That includes Earth. Earth is not special in any way. It is exactly like all other planets in that regard. The probability of life arising on Earth is not special. In fact it is identical to every other planet in the entire universe, and that probability is 1/10^87. There are no conditions that exist in Earth that don’t exist elsewhere. Earth is totally unremarkable. It has exactly the same probability as life arising, and that probability is 1/10^87. Yet because it is so improbable it can’t have arisen elsewhere. So why is it necessary to show that Earth is special when the entire case hinges on Earth being totally ordinary. And since you are here Dio. You still haven’t answered my question. FOR THE SIXTEENTH TIME IN THIS THREAD. Since this is GQ, can you please show us the equations that you used to ascertain these probabilities? Because this is GQ, and not the forum for baseless opinions, so you must have calculated such probabilities before declaring what they are smaller than. SIXTEEN TIMES DIO HAS BEEN ASKED THIS QUESTION. ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [November 10, 2010, 5:43am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/36 "2010-11-10T05:43:19Z")
I’ve answered your question several times, including in the post you just replied to, ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [November 10, 2010, 5:43am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/37 "2010-11-10T05:43:26Z")
> [@Diogenes\_the\_Cynic](#): > > [Read the wiki](http://en.wikipedia.org/wiki/Allan_Hills_84001). You mean this part? > [@](#): > > The debate over whether the organic molecules in the meteorite are in fact of exobiologic origin or are due to abiotic processes on Mars or contamination from the contact with Antarctic ice on Earth is still ongoing. You are so out of your league here, **Dio**. You’re just wrong. Please don’t try to do science on this MB. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [November 10, 2010, 5:46am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/38 "2010-11-10T05:46:17Z")
> [@Blake](#): > > I know this can be hard to grasp, because our intuitive mind tells us that if something improbable happens, it must have occurred because of something special in the starting conditions. But that’s not true. Something can be improbable and happen randomly under perfectly standard conditions. > > And of course the fact that it has happened once does not mean that it must happen every time the same conditions prevail. Life could evolve on Earth against all odds despite Earth being a perfectly ordinary rock, or even if Earth is downright inhospitable to the evolution of life. You have assiduously evaded making the bet. It is a pretty straightforward thing. Instead you are using smoke and mirrors to dodge a simple proposition. You did not quote my whole piece where I showed that the conditions to produce the precursors to life have been replicated on a lab table plus a slew of other evidence. You are right that in the end we do not know the real odds. What we do know is there are an epic amount of dice roles possible in the universe. Further, we have good reason to believe we are not “special” such that nowhere else could do what happened here. You took exception in the other thread that no life was more unlikely than life. This despite the evidence we do know that life is tenacious and survives in remarkably unlikely places a human could never exist in right here on earth. You are correct that even if life has a 99.9999999999999999% chance of developing on another planet we cannot say with certainty that it does exist short of going out and finding it. The point though, which again I will note you avoided, is if you had to bet if there where life elsewhere in the universe besides on earth which way would you bet? That is probably the simplest question you have been asked in this discussion and it is the one you refuse to answer. Why is that? You can answer life or no life…just give your reasons for that answer. ---
**Author:** ![Diogenes\_the\_Cynic](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@Diogenes\_the\_Cynic](https://boards.straightdope.com/u/Diogenes_the_Cynic)\ **Post date:** [November 10, 2010, 5:46am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/39 "2010-11-10T05:46:37Z")
> [@John\_Mace](#): > > You mean this part? > > You are so out of your league here, **Dio**. You’re just wrong. Please don’t try to do science on this MB. No, I don’t mean that part. I mean (among other parts) this part: > [@](#): > > In November 2009, a team of scientists at Johnson Space Center, including David McKay, reasserted that there is “strong evidence that life may have existed on ancient Mars”, after having reexamined the meteorite using more advanced analytical instruments now available, in light of the objections that had been made since the biogenic hypothesis for the biomorphs first had been put forward.[17][18] Overall, the team concluded that: > > ``` > None of the original features supporting our hypothesis for ALH84001 has either been discredited or has been positively ascribed to non-biologic explanations.[13] > > ``` > > In addition, they argued that since the original paper was published, the biogenic hypothesis has been “further strengthened by the presence of abundant biomorphs in other Martian meteorites.” That follows a summary of the failures to so far disprove a biotic origin. Life is still the best hypothesis. If you disagree name a better one. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [November 10, 2010, 5:47am UTC](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137/40 "2010-11-10T05:47:22Z")
> [@Voyager](#): > > So, I’ve given a semi-plausible argument for the likeliness of life. No, you haven’t. You’ve just handwaved about viruses (which are non-living but require complex, pre-existing cellular machinery to reproduce)and undefined self-replicating molecules. For you argument to be even semi-plausible you need to tell use where this occurred? On Earth? Another planet? Benthic Oceans? Palagic Oceans Atmosphere? What were the precursors and how did they arise? What was the original self-replicator, and how did it obtain raw materials? When you have answered those very basic questions, with evidence, then you argument will be semi-plausible. At the moment it’s not an argument at all. I’ve read the actual journal articles on this stuff. Your argument has no legs whatsoever because it fails to address the most obvious problems such theories need to address. And you are wrong. We have no idea how life arose. Even the authors in the premier journal sin the field all admit that. [Previous page](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137.md?page=1) [Next page](https://boards.straightdope.com/t/basis-of-sciences-belief-that-extraterrestrial-life-is-likely/560137.md?page=3)