# Are we alone? **URL:** \ **Category:** Great Debates\ **Created:** [May 6, 2011, 5:07pm UTC](https://boards.straightdope.com/t/are-we-alone/580981 "2011-05-06T17:07:47Z")\ **Posts on this page:** 20\ **Page:** 5
**Author:** ![mac\_bolan00](https://avatars.discourse-cdn.com/v4/letter/m/b3f665/32.png) [@mac\_bolan00](https://boards.straightdope.com/u/mac_bolan00)\ **Post date:** [May 10, 2011, 9:17am UTC](https://boards.straightdope.com/t/are-we-alone/580981/81 "2011-05-10T09:17:17Z")
regarding conditions at the time of life formation (assuming terrestial origin,) geologists have at least conceptions. workable constructs. as to how surface conditions were. gas mix in the atmosphere, salinity levels, orogenic activities, when the meteor bombardment finally dropped to manageable levels, when we finally had an oxygen-rich atmosphere. new findings all the time. the oldest green stones point to a formation where seawater was present - indicating that the oceans formed more than a billion years earlier than throught and that life forms (if present then) could have made several evolutionary epochs way ahead of the estimated date of abiogenesis. which reminds me, gotta update (google is your friend.) ---
**Author:** ![Farmer\_Jane](https://avatars.discourse-cdn.com/v4/letter/f/bbe5ce/32.png) [@Farmer\_Jane](https://boards.straightdope.com/u/Farmer_Jane)\ **Post date:** [May 10, 2011, 9:26am UTC](https://boards.straightdope.com/t/are-we-alone/580981/82 "2011-05-10T09:26:51Z")
[Habitable Zone](http://en.wikipedia.org/wiki/Habitable_zone) ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [May 10, 2011, 11:08am UTC](https://boards.straightdope.com/t/are-we-alone/580981/83 "2011-05-10T11:08:43Z")
> [@Blake](#): > > When I say that we have absolutely no idea, I mean that we have absolutely no idea. Except that in your own post, you already present like three. The problem is not so much that we don’t have an idea, it’s merely that we don’t know which idea is right (if any). The fact that there are ideas at all (most of which do not run on – cosmically speaking – all that implausible assumptions) is already some indication that things needn’t be all that unlikely – otherwise, it’d be highly implausible given the short time we’ve been thinking about this stuff that we should’ve come up with anything much at all. But really, the decisive factor is just that the probability for life to arise is finite – the size of the universe takes care of the rest: currently, the most conservative hypothesis in accord with observation is that the universe is flat, and hence, spatially infinite; thus, the most conservative conclusion is that we are not alone. Whether we ever will be able to interact with other life – which is highly unlikely given even the most optimistic estimates – is quite another story though. With regard to what **Lemur866** said, there already _is_ evidence for non-terrestrial life; it’s just that, given the implications of the discovery, it’s far from conclusive. But still, we have: the [Viking experiments](http://en.wikipedia.org/wiki/Viking_biological_experiments), [methane](http://en.wikipedia.org/wiki/Atmosphere_of_Mars#Methane) and formaldehyde in Mars’ atmosphere, [three](http://en.wikipedia.org/wiki/ALH84001) [Martian](http://en.wikipedia.org/wiki/Nakhla_meteorite) [meteorites](http://en.wikipedia.org/wiki/Shergotty_meteorite), the Martian ‘[dune spots](http://en.wikipedia.org/wiki/Geysers_on_Mars#Hypothetical_biological_origin)’, and if you want to get a little farther out there, there’s always the [Wow!-signal](http://en.wikipedia.org/wiki/Wow!_signal). ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [May 10, 2011, 12:06pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/84 "2011-05-10T12:06:14Z")
> [@Half\_Man\_Half\_Wit](#): > > Except that in your own post, you already present like three. The problem is not so much that we don’t have an idea, it’s merely that we don’t know which idea is right (if any). The practical distinction between “we have absolutely no idea” and "we absolutely can not know which idea is right (if any), eludes me. > [@](#): > > The fact that there are ideas at all (most of which do not run on – cosmically speaking – all that implausible assumptions) is already some indication that things needn’t be all that unlikely – otherwise, it’d be highly implausible given the short time we’ve been thinking about this stuff that we should’ve come up with anything much at all. Yeah right. Within 24 hours of the Spetember 11 attacks the internet was filled with wild speculative conspiracies, many of which are still believed to this day. So that must mean that the attacks really were part of a shadowy concpiracy – otherwise, it’d be highly implausible given the short time they’d been thinking about this stuff that they should’ve come up with anything much at all. I could equally use examples of the Americas being populated by fantastical creatures, the ability of nuclear bombs to produce all sorts of mutations and dozens of other examples of where people came up with preposterous bullshit given much shorter time periods to think about it. The idea that the ability of humans to come up with wide ranges of wild ideas in short periods of time is somehow indicative that the ideas must be likely deserves only one reaction: :dubious: > [@](#): > > But really, the decisive factor is just that the probability for life to arise is finite – the size of the universe takes care of the rest: currently, the most conservative hypothesis in accord with observation is that the universe is flat, and hence, spatially infinite; thus, the most conservative conclusion is that we are not alone. Which is simply a non-sequitur. I contend that the decisive factor just that the probability for life to arise is finite – the size of the universe takes care of the rest: currently, the most conservative hypothesis in accord with observation is that the universe is flat, and hence, spatially infinite; thus, the most conservative conclusion is that we \*are \*alone. Since neither conclusion is in any way linked to the preceeding factors they are both equally correct. > [@](#): > > With regard to what **Lemur866** said, there already _is_ evidence for non-terrestrial life; it’s just that, given the implications of the discovery, it’s far from conclusive. But still, we have: the [Viking experiments](http://en.wikipedia.org/wiki/Viking_biological_experiments), [methane](http://en.wikipedia.org/wiki/Atmosphere_of_Mars#Methane) and formaldehyde in Mars’ atmosphere, [three](http://en.wikipedia.org/wiki/ALH84001) [Martian](http://en.wikipedia.org/wiki/Nakhla_meteorite) [meteorites](http://en.wikipedia.org/wiki/Shergotty_meteorite), the Martian ‘[dune spots](http://en.wikipedia.org/wiki/Geysers_on_Mars#Hypothetical_biological_origin)’, and if you want to get a little farther out there, there’s always the [Wow!-signal](http://en.wikipedia.org/wiki/Wow!_signal). By such standards of “evidence” the Earth was visited by ancient astronauts. Grasping at straws is not evidence. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [May 10, 2011, 12:48pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/85 "2011-05-10T12:48:45Z")
> [@Blake](#): > > The practical distinction between “we have absolutely no idea” and "we absolutely can not know which idea is right (if any), eludes me. Quite simple: total number of ideas in case 1: 0; total number of ideas in case 2: \>0. In the first case, no way to accomplish the development of life has been conceived off; in the second one, the only question is which one (if any) is realized in nature. > [@](#): > > I could equally use examples of the Americas being populated by fantastical creatures, the ability of nuclear bombs to produce all sorts of mutations and dozens of other examples of where people came up with preposterous bullshit given much shorter time periods to think about it. Are you really equating the research efforts on abiogenesis with conspiracy theories, comics, and the like, just to be able to dismiss it all as ‘preposterous bullshit’? Besides, you’ve missed the fact that of all the theories floating through the ether after 9/11, one turned out to be pretty much on the money. > [@](#): > > I contend that the decisive factor just that the probability for life to arise is finite – the size of the universe takes care of the rest: currently, the most conservative hypothesis in accord with observation is that the universe is flat, and hence, spatially infinite; thus, the most conservative conclusion is that we \*are \*alone. In an infinite universe, anything with a probability greater than 0 (like, for instance, the development of life) can be expected to occur infinitely often – not sure what you didn’t get about that. > [@](#): > > By such standards of “evidence” the Earth was visited by ancient astronauts. > > Grasping at straws is not evidence. So, show me where I said that the evidence supports the conclusion that extraterrestrial life exists? Otherwise, knocking down strawmen is not debate. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [May 10, 2011, 1:20pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/86 "2011-05-10T13:20:20Z")
> [@Half\_Man\_Half\_Wit](#): > > Quite simple: total number of ideas in case 1: 0; total number of ideas in case 2: \>0. In the first case, no way to accomplish the development of life has been conceived off; in the second one, the only question is which one (if any) is realized in nature. This has now become ridiculous. All humans have always had \*ideas \*about how the first life developed. You are arguing pointless semantics, and I have no interest in that. Some people had an \*idea \*that life developed when one god cut off another god’s wedding tackle. Your suggestion that I am wrong to claim that such people have absolutely no idea how life developed is ludicrous. You are engaging in a meaningless semantic game, and that sort of disingenuous nonsense bores me shitless. > [@](#): > > Are you really equating the research efforts on abiogenesis with conspiracy theories, comics, and the like, just to be able to dismiss it all as ‘preposterous bullshit’? I am equating them based on your own standard: that when people can come up with ideas rapidly, such ideas must be likely to be true. Either that standard is correct or it isn’t. I believe it is clearly not correct. However since you do believe it then you must also believe in conspiracy theories. And if your own standard can not be applied to idea that we all agree are preposterous bullshit then it is clearly useless. Or to put its simply, the argument that leads you to believe that abiogenesis theories must likely be true also forces you to believe that preposterous bullshit is also true. As such I have demonstrated that it is a worthless argument and it can be rejected henceforth. > [@](#): > > Besides, you’ve missed the fact that of all the theories floating through the ether after 9/11, one turned out to be pretty much on the money. Yes, and none of the ideas about atomic bombs producing giant women, invisible men or giant ants was on the money. So what is your point? > [@](#): > > In an infinite universe, anything with a probability greater than 0 (like, for instance, the development of life) can be expected to occur infinitely often – not sure what you didn’t get about that. [I didn’t get it because it is simply wrong, mathematically, logically and philosophically.](http://boards.straightdope.com/sdmb/showthread.php?t=585020) If an event approaches infinite improbability then even in an infinite universe it will occur a finite number of times. > [@](#): > > So, show me where I said that the evidence supports the conclusion that extraterrestrial life exists? WTF? 😕 “there already is evidence for non-terrestrial life” > [@](#): > > Otherwise, knocking down strawmen is not debate. What you said: “there already is evidence for non-terrestrial life” What I claimed you said: “evidence exists for non-terrestrial life” In what way is this a mischaracterisation of your position. Please, enlighten me. Do you or do you not claim that there is evidence for non-terrestrial life? ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [May 10, 2011, 1:23pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/87 "2011-05-10T13:23:02Z")
> [@Lemur866](#): > > The problem is that we have exactly one sample, which seems like a lot of information. But if that sample didn’t exist, we wouldn’t be here to observe the sample. So that proves that our sample is a biased sample. So the sensible thing to do is to throw out this sample, since we know it is biased. However, if we throw out this sample, we have no other samples left, which is hard to take. Samples are not particularly useful for a binary question like “does life exist elsewhere?” Your samples are either going to be “no life” which does not help answer the question at all, or “life” which definitively answers the question. Samples only help to answer “how common is life on other planets.” The Drake equation is about probabilities. Estimate the probability of life occurring on other planets, multiply by the number of planets, and that’s your probability of life elsewhere. The only choice we have to estimate the probability is to use the Earth, and our knowledge of how life could have begun here. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [May 10, 2011, 1:44pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/88 "2011-05-10T13:44:11Z")
> [@Blake](#): > > I am equating them based on your own standard: that when people can come up with ideas rapidly, such ideas must be likely to be true. Finding plausible solutions is a measure of the hardness of problems. Note that I said plausible – not anything you can conjur up out of nothingness and wishful thinking is plausible, but modern theories on abiogenesis are. Your equating them with 9/11 conspiracies or myths is frankly ridiculous. > [@](#): > > [I didn’t get it because it is simply wrong, mathematically, logically and philosophically.](http://boards.straightdope.com/sdmb/showthread.php?t=585020) If an event approaches infinite improbability then even in an infinite universe it will occur a finite number of times. Great! But note that I said ‘finite probability’. Anything of finite probability is expected to occur infinitely often given infinitely many opportunities to do so. > [@](#): > > “there already is evidence for non-terrestrial life” “it’s just that […] it’s far from conclusive”; i.e. I explicitly said that the present evidence is insufficient to support a belief in extraterrestrial life. > [@](#): > > What you said: “there already is evidence for non-terrestrial life” > What I claimed you said: “evidence exists for non-terrestrial life” No, what you claimed I said, implicitly through claiming that if I were to follow my logic, I ought to believe in ancient astronauts, was that given the evidence, one ought to believe in extraterrestrial life; i.e. the opposite of what I did say. > [@](#): > > Do you or do you not claim that there is evidence for non-terrestrial life? I do claim there is, but not enough to support the hypothesis of its existence. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [May 10, 2011, 2:14pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/89 "2011-05-10T14:14:42Z")
> [@Half\_Man\_Half\_Wit](#): > > Note that I said plausible No, you said that the mere fact that people invented so many ideas so fast actually made the ideas \*more \*plausible. That argument is nonsense, as I have shown. Nobody ever disputed that they are plausible. > [@](#): > > Your equating them with 9/11 conspiracies or myths is frankly ridiculous. No, it isn’t, as I just demonstrated. The fact that your only rebuttal is to repeat the same assertion that i just debunked is really all that needs to be said. > [@](#): > > Great! But note that I said ‘finite probability’. Anything of finite probability is expected to occur infinitely often given infinitely many opportunities to do so. No, as I just demonstrated, that is absolutely incorrect mathematically, logically and philosophically. An event that approaches infinite improbability has a finite probability, and given infinitely many opportunities to do occur it will still occur a finite number of times. Do you not understand this, or do you believe that you can demonstrate mathematically that it is untrue? Because it is rather trivial to demonstrate that it is true. > [@](#): > > “it’s just that […] it’s far from conclusive”; i.e. I explicitly said that the present evidence is insufficient to support a belief in extraterrestrial life. So you claim that “there… is evidence for non-terrestrial life” but the evidence does not “support the conclusion that extraterrestrial life exists”. Care to explain this one to us? Because it makes no sense at all logically or linguistically. How can we have evidence that A exists, and yet the evidence not support the conclusion that A exists? :dubious: > [@](#): > > No, what you claimed I said, implicitly through claiming that if I were to follow my logic, I ought to believe in ancient astronauts, was that given the evidence, one ought to believe in extraterrestrial life; i.e. the opposite of what I did say. No, I never said or implied any such thing. You stated outright that “there… is evidence for non-terrestrial life”. I am still waiting fr you to explain how you can believe that we have evidence that non-terrestrial life exists, and yet this evidence does not support the conclusion that non-terrestrial life exists. At this stage I am sure that I am not the only one who is totally baffled by this apparent contradiction. > [@](#): > > I do claim there is [evidence for non-terrestrial life?]… So why did you ask me to “show [you] where [you] said that the evidence supports the conclusion that extraterrestrial life exists”. How can evidence that A exists \*not \*support the conclusion that A exists? I am now utterly mystified as to what position your are arguing or even what you intended to establish by introducing this “evidence” that apparently does not support the very state that is supposed to be evidence _of_. How can it even _be_ evidence of a state when it does not support the existence of that state? Evidence \*means \*“that which demonstrates a position”. If “there… is evidence for non-terrestrial life” then how can it not demonstrate the position that non-terrestrial life exists? 😕 ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [May 10, 2011, 2:44pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/90 "2011-05-10T14:44:54Z")
> [@Blake](#): > > No, Yes: [QUOTE=me] most of which do not run on – cosmically speaking – all that implausible assumptions [/QUOTE] > [@Blake](#): > > No, it isn’t, as I just demonstrated. Oh, come on. You do see the difference between a scientific theory and some conspiracy whackjob crap, right? > [@](#): > > Do you not understand this, or do you believe that you can demonstrate mathematically that it is untrue? Because it is rather trivial to demonstrate that it is true. Mathematically, it’s absolutely true that anything with a finite probability, in the limit of infinitely many trials, occurs infinitely often. That’s basically what finite probability means (though some people have qualms talking about ‘infinitely many trials’). You’ve probably gotten confused with notions of ‘infinitesimal probabilities’, or alternatively measure-zero sets (which can be seen as sets from which is is ‘infinitely unlikely’ to pull an element by chance – any finite subset of an infinite set is of this sort), but those notions don’t apply here. > [@](#): > > So you claim that “there… is evidence for non-terrestrial life” but the evidence does not “support the conclusion that extraterrestrial life exists”. > > Care to explain this one to us? > > Because it makes no sense at all logically or linguistically. How can we have evidence that A exists, and yet the evidence not support the conclusion that A exists? :dubious: Well, if the evidence is not sufficient, basically. Think about a statistical experiment – drawing coloured balls out of an urn. Say you have two competing hypotheses about the content of the urn: either there are only black balls present, or half of all balls are white. So you draw a ball out – and it’s black. This is evidence in favour of the first hypothesis; but it is not sufficient evidence to accept it. You’d have to continue pulling out balls, and at some point, if you continue drawing black balls, you can accept the hypothesis with a certain confidence. With the extraterrestrial hypothesis, we are very far from the point of being able to accept it with any great degree of confidence; but that doesn’t mean that there is no evidence for it. > [@](#): > > No, I never said or implied any such thing. Ok, this is really devolving into a silly game of he-said-she-said, but you definitely claimed that by my standards of evidence, the Earth was visited by ancient astronauts, which obviously implies that I claim that the evidence I presented necessitates the belief in extraterrestrial life, as otherwise you should have claimed that by my standards of evidence, the Earth _wasn’t_ visited by ancient astronauts, which you, you know, didn’t. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [May 10, 2011, 3:17pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/91 "2011-05-10T15:17:21Z")
> [@Half\_Man\_Half\_Wit](#): > > Yes: Well this is too easy to prove: “The fact that there are ideas at all …is …indication that things needn’t be all that unlikely – otherwise, it’d be highly implausible given the short time we’ve been thinking about this stuff that we should’ve come up with anything much at all.” So yeah, you did say that the mere fact that people invented so many ideas so fast actually made the ideas more plausible. The fact that you are now trying to deny it really speaks volumes about your position. > [@](#): > > Oh, come on. You do see the difference between a scientific theory and some conspiracy whackjob crap, right? As I just demonstrated, by \*your \*standard there is no difference. \*Your \*standard requires us to say that they is no difference between them. That is the whole point. \*Your \*standard is flawed because it forces \*you \*to consider them the same. > [@](#): > > Mathematically, it’s absolutely true that anything with a finite probability, in the limit of infinitely many trials, occurs infinitely often. Cite! You are simply wrong on this issue and, as I said, it is trivially easy to prove. Let the probability of life occurring on any given planet equal 1/l, where l = n^18 and n = the number of planets sampled. 1/l is a finite probability. That is an inarguable fact. So, since we have a finite probability, you can tell me at what number of trials (ie planets) that probability will equal 1. You claimed that the event occurs an infinite number of times, so it must at some point reach unity. So tell me, at what value this occurs? Of course you can not do so, because it never even approaches unity. The value, while provably finite, only ever approaches infinite improbability. It never becomes infinitely improbable, and hence always remains finite, but it never reaches unity. Such an event can therefore never occur an infinite number of times, despite having a finite probability. QED. I await your mathematical demstration that this is incorrect, or a cite to support your claim. > [@](#): > > That’s basically what finite probability means… Cite. It does not mean that at all. > [@](#): > > You’ve probably gotten confused with notions of ‘infinitesimal probabilities’, or alternatively measure-zero sets (which can be seen as sets from which is is ‘infinitely unlikely’ to pull an element by chance – any finite subset of an infinite set is of this sort), but those notions don’t apply here. I am not confused at all. I am simply speaking of finite, clearly defined probabilities. I have given you one, and since you have told me that such an event must occur, not just once but an infinite number of times, I await your answer as to the point at which its probability becomes unity. > [@](#): > > Well, if the evidence is not sufficient, basically. So does the observation support the existence of extra terresirial life or not? > [@](#): > > This is evidence in favour of the first hypothesis So it is evidence in support of the hypothesis? So what relevance does it have to your assertion that it is \*not \*evidence in support of the hypothesis? > [@](#): > > With the extraterrestrial hypothesis, we are very far from the point of being able to accept it with any great degree of confidence; but that doesn’t mean that there is no evidence for it. So after all that, you still have not answered the question: **is their evidence in support of the conclusion that extra-terrestrial life exists, or is there not**? Simple question, can we have a simple answer? > [@](#): > > … you definitely claimed that by my standards of evidence, the Earth was visited by ancient astronauts, which obviously implies that I claim that the evidence I presented necessitates the belief in extraterrestrial life.. No, it does not imply that in any way at all. It implies that your standard of evidence is flawed because it leads you to accept conclusions that we all agree are incorrect. That is all. Now can you please answer the questions: 1: Given a probability of life occurring on any planet equal 1/l, at what number of trials (ie planets) will the probability of finding life equal unity? 2: Does the mere fact that people invent many ideas fast actually make the ideas more plausible? 3: Does evidence exist that supports the existence of extra-terrestrial life, or does no evidence exist that supports the existence of extra-terrestrial life? Because you have made both these claims, and they can not both be true. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [May 10, 2011, 3:43pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/92 "2011-05-10T15:43:50Z")
**Blake** , I’m afraid I lack your motivation and energy to carry on with this nonsense, plus it’s really not all that important to me. I’ve made three simple points, behind which I stand: 1. The fact that we can come up with plausible scenarios for abiogenesis means that it’s probably not all that hard a problem. Your quoting me out of context and with clearly obfuscatory intent won’t change anything about this simple conclusion. 2. Anything with a finite, _fixed_ probability will, given infinitely many occasions, occur infinitely often. True, I didn’t specify fixed, but unless you give a good reason why the probability of life occurring should depend on the number of planets, I’ll just continue assuming it doesn’t, as probably everyone else does if they’re not out to desperately ‘win’ a point in an internet discussion. 3. There is evidence, but it is (wildly) insufficient evidence. WTF’s so difficult about that? You’re very welcome to throw your impressive rhetorical skills at this, too; just don’t expect me to care. ---
**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:** [May 10, 2011, 4:39pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/93 "2011-05-10T16:39:42Z")
> [@sleestak](#): > > Just gotta comment on this. There is no reason to assume that any intelligent race that may exist would have any idea of ethics, much less ethics that mirrors our own. Heck, I’d bet that there are a fair number of humans who, if we located an alien intelligent race, would be all for killing 'em all and taking all their loot (if we could do it). Ethics is just a system that allows intelligent entities to live together. Any alien race will have a system of ethics, though it might be different from ours. For instance, if alien women had litters of 12, it might be ethical for them to allow only the strongest to live. I don’t disagree with you on our attitude. If we didn’t have this kind of attitude, we might be spending the money we spend on weapons on space travel, and we might be the ones doing the contacting. > [@](#): > > It’d be nice to think that the Star Trek non-interference ideal is universally held but since we can’t even agree on that ourselves it doesn’t make any sense to assume any other intelligent life forms would follow it. Ever read **The High Crusade**? Aliens might think it a really bad idea to let warlike cultures get a hold of advanced technology. I’m certainly not claiming this is the answer - it is a possible answer. ---
**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:** [May 10, 2011, 4:45pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/94 "2011-05-10T16:45:33Z")
> [@Blake](#): > > Wrong on both counts. > > No, it is not higher, and prions and viruses are not intermediate stages between life and non-life. The source I’ve read say that viruses are not alive. We’ve built viruses from more or less scratch, which is not considered creating life. Of course viruses are not an intermediate form - they are highly evolved over the past billion years or so, and are dependent on living things for existence. The point is that viruses, more primitive than actual life, evolve, which indicates that in the early earth self-replicating molecules could also have evolved, before what we call life began. ---
**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:** [May 10, 2011, 4:53pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/95 "2011-05-10T16:53:51Z")
> [@Blake](#): > > Ahhh, no. They evolved \*from \*living things. They are no more examples of protolife than your eyeballs or any other part of your body that has also “evolved to be dependent on truly living things”. By some standards viruses are the most highly evolved lifeform on the planet. There is certainly no doubt that they are descended form living cells, rather than being some sort of proto-life. > And what is that good reason? It would help if you read what I wrote and not your fantasy of what I wrote. I specifically said that viruses are highly evolved, and that they no longer exist on their own. (They do in stasis, as it were, but they wouldn’t reproduce.) As I said before, we have examples of reproducing forms that are much simpler than cells. I’m not saying that they were the precursors of cells - they are evidence that such things can exist, reproduce, and evolve. Certainly if viruses can evolve very sophisticated methods of invading cells, this proto-life could evolve means of getting “food” in the form of organic molecules. And while we probably won’t know for certain how life on earth evolved, having a number of plausible mechanisms for it means that the probability of life evolving is higher than if we had no plausible mechanisms at all. ---
**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:** [May 10, 2011, 5:07pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/96 "2011-05-10T17:07:32Z")
> [@Blake](#): > > Well this is too easy to prove: > > “The fact that there are ideas at all …is …indication that things needn’t be all that unlikely – otherwise, it’d be highly implausible given the short time we’ve been thinking about this stuff that we should’ve come up with anything much at all.” > > So yeah, you did say that the mere fact that people invented so many ideas so fast actually made the ideas more plausible. > > The fact that you are now trying to deny it really speaks volumes about your position. What speaks volumes about your position is that you are unwilling to recognize the difference between the existence of several scientifically supported hypotheses about abiogenesis and myths. Do you accept that several plausible explanations make the probability of abiogenesis not as incredibly tiny as you seem to be claiming? Since the universe is finite, we could compute the odds of a single planet with lfe universe given a small enough p. But the existence of these hypotheses and our understanding of the basic constituents of life make it pretty clear that p isn’t that small. You are invited to give some reasons for a infinitesimal p beyond the mere assertions that you have been giving so far. ---
**Author:** ![Paranoid\_Randroid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/paranoid_randroid/32/18_2.png) [@Paranoid\_Randroid](https://boards.straightdope.com/u/Paranoid_Randroid)\ **Post date:** [May 10, 2011, 7:54pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/97 "2011-05-10T19:54:47Z")
> [@Voyager](#): > > The Drake equation is inherently probabilistic. That 50% of stars have planets says nothing absolute about whether any of them have life, but this is certainly more likely than if 1% of stars have planets. Of course, although I wasn’t speaking in terms of the Drake equation. What I don’t quite understand is a statement like this: > [@](#): > > But the existence of these hypotheses and our understanding of the basic constituents of life make it pretty clear that p isn’t that small. An estimate of the probability of life arising, p, is surely subject to a great deal of uncertainty. It won’t do just to argue that p “should be” high; we must account for the uncertainty (say by assigning a prior distribution to p); and it isn’t clear to me what that should even _look like_. But even were we willing to give some informative prior to p, it could still lie anywhere over [0, 1]. So I am unsure whether this whole argument has any point, unless someone would like to point to some more precise knowledge about the distribution of p. ---
**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:** [May 10, 2011, 8:11pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/98 "2011-05-10T20:11:05Z")
> [@Paranoid\_Randroid](#): > > Of course, although I wasn’t speaking in terms of the Drake equation. What I don’t quite understand is a statement like this: > > An estimate of the probability of life arising, p, is surely subject to a great deal of uncertainty. It won’t do just to argue that p “should be” high; we must account for the uncertainty (say by assigning a prior distribution to p); and it isn’t clear to me what that should even _look like_. But even were we willing to give some informative prior to p, it could still lie anywhere over [0, 1]. So I am unsure whether this whole argument has any point, unless someone would like to point to some more precise knowledge about the distribution of p. We certainly cannot assign an absolute value to p, or even much of a range. Since the question is whether there is other life in the universe, not how many other worlds have life, we should be satisfied if p is greater than some very small number which would make the probability of this sufficiently small. So, what would a very small p look like? If the 747 in a junkyard tornado analogy was correct, and the simplest form of independent life were a cell, I think that would count. (Dawkins does also.) If the smallest self-replicating molecule were very complex, that might count also, since you compute the probability that such a molecule would come into being through the random mixing of its components given some primordial soup. If however, there are fairly simple self-replicating molecules, and/or there are mechanisms which encourage their being built (like clay) p is much higher. My virus example was to demonstrate that something didn’t have to be as complex as a cell in order to evolve. ---
**Author:** ![Lance\_Turbo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lance_turbo/32/6156_2.png) [@Lance\_Turbo](https://boards.straightdope.com/u/Lance_Turbo)\ **Post date:** [May 10, 2011, 9:36pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/99 "2011-05-10T21:36:37Z")
> [@Blake](#): > > Let the probability of life occurring on any given planet equal 1/l, where l = n^18 and n = the number of planets sampled. > > 1/l is a finite probability. I agree with the overall point you are trying to make in this thread **Blake** but you’re incorrect here. The above is by definition an infinitesimal probability since it can be smaller than any positive epsilon we choose when n is large enough. Finite is generally defined as neither infinite nor infinitesimal. ---
**Author:** ![gonzomax](https://avatars.discourse-cdn.com/v4/letter/g/e8c25b/32.png) [@gonzomax](https://boards.straightdope.com/u/gonzomax)\ **Post date:** [May 10, 2011, 10:44pm UTC](https://boards.straightdope.com/t/are-we-alone/580981/100 "2011-05-10T22:44:02Z")
[http://explore.wingsworldquest.org/?q=node/440](http://explore.wingsworldquest.org/?q=node/440) The Drake equations preceded the discovery of exremophiles. We have discovered life at the vents of volcanoes at the bottom of oceans. We have discovered some extremophiles that live in horrible cold. Others thrive in strong salt water that should not allow life. I have read about some living near nuclear reactors. Life seems to get a foothold in places and conditions that logic would say is impossible. [Previous page](https://boards.straightdope.com/t/are-we-alone/580981.md?page=4) [Next page](https://boards.straightdope.com/t/are-we-alone/580981.md?page=6)