This artist's illustration gives an impression of how common planets are around the stars in the Milky Way. Credit: NASA, ESA, and M. Kornmesser (ESO)

We Really Hope ET is Out There, But There’s Not Enough Scientific Evidence, Researchers Say

Article Updated: 23 Dec , 2015
by

[/caption]

For many of us who grew up listening to Carl Sagan, watching robotic spacecraft travel to other worlds, and indulging in science fiction books and movies, it’s a given: one day we’ll find life somewhere else in the solar system or Universe. But are we being too optimistic? Two researchers say that our hopes and expectations of finding ET might be based more on optimism than scientific evidence, and the recent discoveries of exoplanets that might be similar to Earth are probably getting everyone’s hopes up too high.

Astrophysicist Edwin Turner from Princeton and researcher David Spiegel from the Institute for Advanced Study say the idea that life has or could arise in an another Earth-like environment has only a small amount of supporting evidence, most of it extrapolated from what is known about abiogenesis, or the emergence of life, on early Earth. Their research says the expectations of life cropping up on exoplanets are largely based on the assumption that it would or will happen if the same conditions as Earth exist elsewhere.

Using a Bayesian analysis — which weighs how much of a scientific conclusion stems from actual data and how much comes from the prior assumptions of the scientist — the duo concluded that current knowledge about life on other planets suggests Earth might be a cosmic aberration, where life took shape unusually fast and furious. If so, then the chances of the average terrestrial planet hosting life would be low.

“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,” Turner said.

So, if a scientist starts out assuming that the chances of life existing on another planet is as large as on Earth, then their scientific results will be presented in a way that supports that likelihood, Turner said.

“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.

Therefore, with all the exoplanets being found, and as our discoveries have become more and more enticingly Earth-like, these planets have our knowledge of life on Earth projected onto them, the researchers said.

How does an exoplanet researcher feel about this? Turner and Spiegel found a sympathetic soul in Joshua Winn from the Massachusetts Institute of Technology, who said that the two cast convincing doubt on a prominent basis for expecting extraterrestrial life.

“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.

It is true that science is about facts — not about what your gut feelings are. But there’s a strong argument that we need inspiration to do the best, most engaging science. Writer Andrew Zimmerman Jones blogged today at PBS about how many scientists were spurred to follow their careers by reading science fiction when they were young.

“The finest science fiction is inspired by the same thing that has inspired the greatest science discoveries throughout the ages: optimism for the future,” wrote Jones.

And perhaps that is what is mostly behind our hopes for finding ET: optimism for the future of the human race, that we really could one day travel to other worlds, and find new friends — “to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no one has gone before…”

Turner and Spiegel do say they are not making judgments, but just analyzing existing data that suggests the debate about the existence of life on other planets is framed largely by the prior assumptions of the participants.

“It could easily be that life came about on Earth one way, but came about on other planets in other ways, if it came about at all,” Turner said. “The best way to find out, of course, is to look. But I don’t think we’ll know by debating the process of how life came about on Earth.”

Read the team’s paper.

Sources: Princeton, PBS

, , ,



86 Responses

  1. Zoutsteen from Holland says:

    WHEN … we find life, one of the things that will happen is information exchange.
    Should we send Harry Potter stories or Freud as most informative about who we are?

  2. NoAstronomer says:

    Blah! Bayesian analysis has certainly proved useful in examing many areas. This is not one of them.

    • SJStar says:

      Blah! No astronomer, and clearly no scientist.
      Clearly, the only Bayesian analysis you know is curing a headache with a brand of aspirin!

  3. gekkehenkie says:

    saying life must be common or else it would not have arisen so quickly after the surface of the Earth cooled.
    Is just like if i say complex life needs a moon, because the only planet with complex life that we know of has a moon. We just need to know how life started on this planet before we can say how many other planets have life.

    how many worlds inside the habitable zone have life.
    it could be 1 on 2 or 1 on 10 or 1 on 10000.
    We just do not know yet.

  4. bfmorris says:

    I’m not sure that life (if) found elsewhere in our own local system should be considered a second sample, either, given the obvious possibility of interplanetary contamination due to asteroid strikes or other means. Regarding other means, I remember a paper years ago that suggested Earth is literally leaving a trail of microbes in space as it moves.

    • squidgeny says:

      Interesting! But I think that could only happen if microbes bobbed up to the top of the atmosphere and obtained escape velocity…. a horrendously improbable occurance. As far as I know, only hydrogen does that.

      • Duncan Ivry says:

        Interesting, indeed! When you consider the many heavy asteroid bombardments in earth’s history, wouldn’t you think it’s plausible that some microbes escaped earth.

      • SJStar says:

        …and you know this how?

        What ridiculous and totally felicitous argument!

        No. No sane person would consider it. Let’s see… Escaping into the vacuum of space, being frozen solid, surviving aeons is space without nutrients or water, then happen to find a planet that will support you… Now is THAT, TOO, plausible?

      • Mark O says:

        Yes.

      • SJStar says:

        Eh? I was pointing out the obfuscation here!

  5. Abraham Samma says:

    “The best way to find out, of course, is to look. But I don’t think we’ll know by debating the process of how life came about on Earth.”

    This is most interesting. We of course aren’t entirely sure how E.T.s look like, how their biochemistry functions and so on. In the end, Earth only shows us that it was possible for THIS kind of life to develop HERE. Some other type of freaky chemistry could cause life to emerge elsewhere though again we haven’t the foggiest idea. Best thing is to keep looking as they suggest I believe wholeheartedly.

  6. Well, if we go on the assumption that life does’nt exist elsewhere in the cosmos, we may aswell stop looking then. (Sarcasm). Fact is, we hardly know a thing about our 2 nearest neighbours Venus & Mars let alone Planets outside our own solar system so for someone to be so blank minded on this is just stupid. In my opinion, the only question is, is how far up the evolutionary tree are we?

    • SJStar says:

      You, like some of the others here, don’t understand implication of the question.

      Surely the answer of their theory is come up with testable observations to prove or disprove their conclusion. You may disagree with their conclusion on other grounds, but their general premise is correct. We only see one example of life in the universe, and that is here on Earth. We have a sample of one on the CURRENT EVIDENCE. That conclusion is the only one that is irrefutable.

      • Zoutsteen from Holland says:

        … Looking back into history tells us Earth definitely wasn’t the best to life …
        On that idea: who knows what a “gentle” planet would spawn?

      • SJStar says:

        Agreed. Your point?

      • Zoutsteen from Holland says:

        I know that when I use a set mix of ingredients and place them in an oven, I’ll always end up with cookies.
        With the basic ingredients and an oven available, you can expect more cookies, if not bread, cakes or apple pies.

        The basic assumption in this is that life spawned from chemistry.
        Not something unique to Earth.

        So anyone even remotely suggesting we’re alone has to come up with better than what I read.

      • SJStar says:

        Sigh. “The basic assumption in this is that life spawned from chemistry. Not something unique to Earth.”

        It is something unique for the Earth, as we have no other proof of life anywhere else in the Universe. Period.

        Unless you have direct proof that life exists in other places in the Universe. Ergo, you assumption is plainly wrong!

        Why don’t you get that very simple fact??

      • Zoutsteen from Holland says:

        That is where you miss 1 point.

        You assume that the lack of proof is a fact. In this case it is not.

        Transmission: Someone with higher knowledge of the required energy output to send a signal everywhich way at a high enough level for us to already have received it might convince you that its cheaper to search passively and after receiving signs of possible life transmit actively than do the other way round.

        Science: We’re definitely not on a high scientific level enough to see more than sun/planet interaction. Either the wobbles or the dimming of sunlight is best we’re getting at the moment. It doesn’t proof or disproof or factualise anything.

        Hence: we make assumptions based on our best knowledge we have. And expanding on that gives us plenty of reason that the assumption of life elsewhere is a valid assumption.

      • SJStar says:

        “You assume that the lack of proof is a fact.”

        Eh? We have found no other indigenous life in the Universe. Fact!!!!

      • Zoutsteen from Holland says:

        Another fact is that we hadn’t found any extra solar planets upto ~20 years ago.

        Is it a sensible fact? Or just something noteworthy for history books?

        But I’m gonna leave this as it is SJStar. See you at some other topic.

      • SJStar says:

        Again. This is irrelevant… We have found no other indigenous life in the Universe.
        Discovering other planets is irrelevant to the existence of life….

    • squidgeny says:

      I’m not sure you understand the article. The scientists are suggesting that others are being too optimistic – they’re not ruling out the possibility.

      That’s what good science is about.

  7. Torbjörn Larsson says:

    This is the publication of their arxiv paper of 19 July which we discussed at length at the time. There you can get a link to the pre-review version.

    While I haven’t readied something akin to a detailed analysis, the basic problem with their analysis is that they have to assume that abiogenesis can’t be a generic process but is widely different on different planets:

    “Between these limiting times, we posit that there is a certain probability per unit time (&lambda); of life developing.”

    “If Mars and Earth have different λs and life never arose on Mars, then the likelihood of Mars’ &lambda (case i) is simply taken from Eq. (2), … If Mars and Earth share a single λ and life did arise on Mars, then the likelihood of Mars’ λ (case ii) is the joint probability of our data on Earth and of life arising on Mars. … For case (ii ), we see that, should future researchers and that life arose independently on Mars, this would dramatically reduce the posterior probability of very low λ relative to our current inferences.”

    In sum, if you assume Earth isn’t representative, Earth isn’t representative. Instead we can do the usual hypothesis testing that I described in that thread [slightly edited]:

    “Abiogenesis, having prebiotic chemistry evolve into protobiotic cellular life, could be a repeated process of attempts over time and locales. In the simplest stochastic model this belongs to the family of Poisson processes.

    Such processes stacks their probability mass early, due to their exponential distribution. A homogeneous Poisson process has P(T > t) = e- ?t.

    This is a testable model.

    To simplify we use a normed distribution where observation time t = 1. Since this is a one-sided interval from t = 0, we want to have a set of distributions with at least 0.99 of the probability mass within the interval.

    The probability mass is expressed by the cdf (cumulative distribution function). Inserting into the Poisson cdf, we get F(t,?) = 1 – exp(-t*?) ? 0.99 ? t*? > 4.6.

    Now t = 1 corresponds to ? ~ 5. That means the normed waiting time T ~ 0.2. With actual time t* ~ 5 Gy we get actual waiting time T* ~ 1 Gy.

    With current understanding we have putative observations of life from ~ 3.8 – 3.5 Gy ago. Earth aggregated ~ 4.5 Gy ago, which means the interval gets close to the required ? 1 Gy.”

    Then I cover the caveats with this, including those raised by the paper. That can be summed up as:

    “- “What if” the observation had been closer to observation time t?

    Such test wouldn’t have been possible to do with such confidence. That doesn’t affect this test that is to be scrutinized for its failure, not its success.”

    So the generic Poisson model is informative and suggest that, contrary to Spiegel & Turner, abiogenesis is similar, has a similar λ on habitable planets. This is also what chemical models of abiogenesis predicts (see the other comments on that thread).

  8. super_earth says:

    Well all we can say now is just guessing, because we don’t know how life started here on earth (the process is called abiogenesis)

    We have some hypothesis (like the RNA world) and lab experiments (like the production of nucleobases, sugars, aminoacids and fatty acids from simple organic and inorganic chemicals), but we lack any fossil evidence from the young Earth (i.e. when it was less than 100 million years old).

    We know:

    a) The earth was habitable already when it was 100 million years old (evidence from Jack Hills zircons)

    b) Simple biomolecules are formed if the conditions are right (like in carbonaceous chondrites or reducing atmospheres like in Titan)

    We don’t know:

    a) What was the young Earth (i.e <100 million year old) environment (temperature, composition of the atmosphere)?

    b) How the primitive biomolecules assembles to form early biopolymers. In particular, how can nucleotides form abiogenically, and then polymerise to RNA and DNA?

    We have the hypothesis that:

    Early lifeforms were have not a complex DNA-RNA-Protein apparatus, but just RNA. This is called the RNA world hypothesis, and is based on the discovery that RNA can behave as a catalytic enzyme (ribozyme) like modern proteins do. With just RNA inside some lipid vesicle, abiogenesis is believed to be a lot simpler.

    A good (but too short) explanation is here:
    http://exploringorigins.org/index.html

    Is this process difficult or easy? That is, how frequent are the conditions that produce complex biomolecules in the universe?

    We will have no idea until the process of transition from just chemistry to biology is known. Until then, we don’t know what conditions are the ones that lead to life and we will still keep guessing.

    • bfmorris says:

      “We will have no idea until the process of transition from just chemistry to biology is known.”

      Apparently, ‘stochastic processes’ are smarter than we are, having the ability to assemble this bewildering thing we call life. We can’t even reverse engineer it. I don’t know whether to laugh or cry.

      • SJStar says:

        “We will have no idea until the process of transition from just chemistry to biology is known.”

        Try total bewilderment. This particular statement is 100% true!

        So, genius, tell us the process, and a Nobel Prize is going your way!

      • lcrowell says:

        We don’t understand randomness for a basic reason. Think of a symbol string, such as a string formed by H and T for a sequence of coin tosses. A set of symbol strings of length n consists of 2^n distinct strings. These strings qualitatively are random, but of course some are not, such as the one string consisting of n T’s. Some of these as a binary string are halting programs, others are not. Alan Turing told us there is no universal Turing machine (UTM) that can determine the halting status of all possible Turing machines. The UTM has to emulate itself emulating others and this leads to an infinite regress. So we can’t separate the completely random strings from the nonrandom ones in a consistent manner.

        A corresponding result is the Kolmogoroff entropy problem, where the entropy of a string may be determined by another symbol string that is longer, but where this length grows wildly. The symbol string for determining the halting status of all possible strings then is infinite with an infinite entropy measure.

        Most of those strings formed from the coin toss appear random, and if you run a random appearing string through a data compression algorithm you may find it compresses very little. The Halting problem above is equivalent to saying there does not exist a universal compression algorithm which can compress these string to an absolute minimum and select those which do not at all compress. What we are up against is that no deterministic automata can truly function in a random manner. Random number generators are pseudo-random. As a result we are absolutely unable to generate random sets in the way nature does — or appears to do. The reason is that any automata or algorithm is mathematically incapable of computing pure randomness.

        LC

      • bfmorris says:

        So you are saying randomness cannot be conferred because the act of conferring randomness actually ensures that the given program/system is not random.

      • lcrowell says:

        This sounds right. A Turing machine is an absolutely deterministic system. The Chomsky hierarchy of lexical structures or syntaxes its within the Turing thesis of what is computable, and this is extended to something called the Church-Turing theorem of ?-calculus. So randomness is not truly random in an algorithm, for algorithms are deterministic systems that are inherently not random.

        I have written a number of computer programs where I use chaos theory as a random number generator. The standard map or other nonlinear Hamiltonian systems are completely deterministic, but round off errors cause departures from the actual physics. The output then has a chaotic structure that appears random. So the initial conditions of the system are set by some external parameter in the program, and the number of iteration set by another. The outputs are nice pseudo-random numbers. However, this is not really random.

        LC

      • bfmorris says:

        Does your program’s output appear to be purely random to anyone not privy to your program’s initial external parameters, including not having sight of the program’s start or halting? I think the guy buying the computer-generated lotto ticket walks away satisfied that his numbers are random. Of course we know they are not.

      • lcrowell says:

        For a punctured KAM torus it is. A very simple random number generator is the following. Let x = e^{i?}, for some angle determined by an input or assigned by hand, and with each iteration you square it so x — > e^{2i?}. This can be done with trigonometric functions as well say let

        x = cos(?)

        square that x — > = x’ = cos^2(?) and continue n iterations. You cut this off for some index, say the value of an iteration loop you are computing or some other integer. Then output Re(x) in [0, 1]. This will look pretty random for a range of iteration cutoffs.

        LC

      • bfmorris says:

        How can a universe that contains universal laws, and an apparent beginning, have true randomness within itself?

        Perhaps we (ie life) are the sole true random component.

      • lcrowell says:

        Quantum mechanics is where things get strange with this. The Schrodinger wave equation is deterministic, but the amplitudes which modualus squared determine probabilities in a measurement. The actual measurement is completely stochastic. There is no substratum of determinism in the actual outcome. This is Bell’s theorem. So there is some sort of dualism between determinism and dynamics and stochastic principles on the most fundamental level.

        The universe emerged most likely as a quantum fluctuation, where the outcome was completely stochastic.

        LC

    • Brad351 says:

      Well, I’ll see your abiogenesis and raise you a panspermia. The question is, which of those two does Bayesian analysis consider to be more likely. I think I know without needing a math degree…

      • super_earth says:

        Panspermia is just abiogenesis outside planet Earth, followed by the colonization of Earth by the extraterrestrial lifeforms already “abiogenerated” into our planet.

        The most obvious way for this to happen is with meteorites and comets inhabited by bacteria falling to earth. This bacteria could be generated in situ (i.e. abiogenesis happened in the moist and warm minerals of carbonaceous chondrites and comets) or blasted from the surface of other planet (i.e. the meteorites are planetary fragments from an impact, like the martian meteorites).

        Of course this bacteria must survive extreme conditions: the cosmic and solar high energy radiation, temperature extremes and vacuum, but if the bacteria are in the inner part of an asteroid, it would shield them from most of this extremes. Then there are the extremes related to the entry into the atmosphere and impact: thousands of degrees due to atmospheric friction (this obstacle can be passed if the asteroid is big enough) and the explosion due to the impact (a small, few meter size is ideal: if smaller, the hot atmospheric entry will toast the microorganisms, if bigger, the impact will cause an explosion that can vaporize anything in a radius of kilometers, including the asteroid itself).
        Panspermia could be planetary if it is just planets exchanging rocks via impacts, for example, an asteroid hit Mars throwing martian rocks into space that will fall into other planets after millions of years.

        There are some more bold hypothesis that consider that life originates not in planets but already in the small planetesimals of the young solar systems (in our solar system, this means in comets and the parent bodies of carbonaceous chondrites). This second case assumes that abiogenesis is extremely easy, almost unavoidable once the conditions are right and those conditions are just the same as those needed for habitability (presence of liquid water, a source of energy and nutrients).

        In any case, panspermia happens thanks to rock-loving bacteria that can survive for millions of years inside the pores of rocks. These bacteria exist on Earth, so this is certainly a plausible scenario that some of them could be ejected to space during the impact of an asteroid and then fall elsewere (Mars or Europa, for example) and somehow find a place there where they can live(not an easy task in Mars!).

        For Panspermia from comet and chondrite-borne organisms , it is critical if the conditions there (that certainly were habitable in the past for bacteria, there is a lot of evidence of past liquid water and organic matter) were the conditions needed for abiogenesis to occur or not. We just don’t know that.

    • lcrowell says:

      There is a funny part to this. The RNA world needed some way of converting its information into polypeptides. The world was very volcanic and ash probably contained fullerenes and carbon tubes. The RNA would have bound to this as would amino acids. Amino acids doubtless existed by means similar to the Miller-Urey experiment. So these might have served as a primordial ribosome.

      I thought about pursing this as a research program. However, I found that some researchers had jumped on this a couple of years before.

      This RNA world was a free for all. There were free strands of RNA, peptide processes and so forth, all in a small body of water. That might have been a warm spring near a volcanic area.

      LC

  9. Checkers Crossfox says:

    Considering that life developed here pretty much the instant it could (geologically speaking), and that the components that make it up are literally -everywhere- in space, it seems to me a reasonable assumption that it is likely to happen elsewhere, given similar conditions. Yeah, our sample size of life-bearing planets is ‘one’, but that’s not all the data we have to go on, here. XD

    • SJStar says:

      “Yeah, our sample size of life-bearing planets is ‘one’, but that’s not all the data we have to go on, here.”

      This is just a irrational circular argument.

      Also;
      “Considering that life developed here pretty much the instant (geologically speaking)…”

      and you know this… How? (This is strictly a broad brush assumption. I.e. It could have come about by panspermia or another intelligent lifeform, for example!)

      • Checkers Crossfox says:

        Perhaps I should have said “occurred” rather than “developed”, as I suppose that did imply that it necessarily formed here and discounted panspermia. 🙂

        Geochemical evidence suggests that there were biological processes occurring here as far back as 3.8 billion years ago, which is pretty darn quick considering all of what was going on back then. 🙂

      • SJStar says:

        Actually I was not saying panspemia (or another intelligent lifeform) were possibilities. I was only saying to show that life on Earth may have has different options – including others not mentioned. (Personally, I reject both for my own reasons, similar to the logic of this paper/story – but that is not relevant here.)

        The point is we don’t know, and because of this, we cannot extrapolate that the Solar System, our galaxy, the whole Universe is teeming will life or has any life at all!

        In any science experiment, you have to prove your theory, and do another related experiment to be able to confirm your result. With only one example for your data set, means you cannot give a global solution – and you cannot change that unless you find positive evidence of other life elsewhere.

        The rest is speculation, which is the grim reminder or the central point of their published paper and this article .

        Components may or may not be the “components that make it up are literally -everywhere- in space.” That is irrelevant, as they are just chemicals part in space without organisation. Living ‘matter’ by definition is some biological organisation, but how life comes about from matter is not known. A solution is to develop a new lifeform from the chemical constituents – which has not been done or scientifically verified.

        Hence, “Considering that life developed here pretty much the instant (geologically speaking)…” is illogical, because we do not know how life started at all – except that it is here and has likely been evolving for aeons.

        It might be an esoteric point, but it is a fundamentally valid point, which is correct.

        (Do appreciate the ‘similes’, hence the longer reply…)

      • SJStar says:

        Actually I was not saying panspemia (or another intelligent lifeform) were possibilities. I was only saying to show that life on Earth may have has different options – including others not mentioned. (Personally, I reject both for my own reasons, similar to the logic of this paper/story – but that is not relevant here.)

        The point is we don’t know, and because of this, we cannot extrapolate that the Solar System, our galaxy, the whole Universe is teeming will life or has any life at all!

        In any science experiment, you have to prove your theory, and do another related experiment to be able to confirm your result. With only one example for your data set, means you cannot give a global solution – and you cannot change that unless you find positive evidence of other life elsewhere.

        The rest is speculation, which is the grim reminder or the central point of their published paper and this article .

        Components may or may not be the “components that make it up are literally -everywhere- in space.” That is irrelevant, as they are just chemicals part in space without organisation. Living ‘matter’ by definition is some biological organisation, but how life comes about from matter is not known. A solution is to develop a new lifeform from the chemical constituents – which has not been done or scientifically verified.

        Hence, “Considering that life developed here pretty much the instant (geologically speaking)…” is illogical, because we do not know how life started at all – except that it is here and has likely been evolving for aeons.

        It might be an esoteric point, but it is a fundamentally valid point, which is correct.

        (Do appreciate the ‘similes’, hence the longer reply…)

      • Checkers Crossfox says:

        I would rather call it ‘extrapolation’ than ‘speculation’, really. I agree, though, we have no other confirming samples, which really leaves us at the hypothesis stage at best with the whole thing. But looking at what we do know about the universe, what with the ubiquity of planets and organic molecules, and assuming the Copernican principle, I’d call it a pretty reasonable hypothesis. 🙂

        Life -appeared- on Earth very quickly, at least as far as our evidence can show. We can’t yet say exactly how this happened, no. But we know that it did, or, well, we wouldn’t be asking about it. 😉

      • SJStar says:

        Fair enough. 🙂

    • squidgeny says:

      it seems to me a reasonable assumption that it is likely to happen elsewhere, given similar conditions.

      I agree. The trouble is, we don’t have anywhere near a complete list of the chemical ingredients and environmental conditions necessary for life, and without that list we can’t take the next step of determining how likely that list is to be complete for any given planet.

  10. Kawarthajon says:

    This is a little like the pot calling the kettle black, no? The researchers seem to be saying that the data to support life arising on a planet is minimal (n=1), so that means that it is likely that life didn’t arise on other planets. Either way, your data revolves around one planet – how can you say how likely, or not likely, it is that life will arise without any data??? Regardless, this is one of the most interesting and important scientific questions out there and, in my opinion, it is worth looking for life elsewhere.

    • SJStar says:

      That is not what is being said…

    • squidgeny says:

      The researchers seem to be saying that the data to support life arising on a planet is minimal (n=1), so that means that it is likely that life didn’t arise on other planets.

      No, they’re saying that the current data is inconclusive and more data is needed before we assign a high probability to either conclusion.

  11. arthur_gould says:

    Everyone, These guys are wrong. It’s all real simple. Everywhere we look the Universe is comprised of all of the same elements. One look at the Hubble Ultra Deep Field image tells the whole story. To think we are the only biological sentient entities in the Universe is utterly retarded. They should know better to put a paper out like this.

    • SJStar says:

      Oh dear, oh dear… You clearly didn’t read the article nor understand the implications.

      Something simple. Read the main UT title of this story again.

      Also. Please explain in the story what does this to you actually mean; “Using a Bayesian analysis — which weighs how much of a scientific conclusion stems from actual data and how much comes from the prior assumptions of the scientist…”

      • Jon Souter says:

        @SJStar…

        So the analysis suggests we can’t make a scientific conclusion at this point due to lack of evidence.

        And this is news?!

        Other recent research suggests most humans are optimists by nature – even when facing insurmountable odds – it’s effectively what drives us as a species. Therefore, I’m surprised you find people’s thought processes around the possibility of non-terrestrial life so hard to grasp.

        Lack of data doesn’t stop belief, by the brightest scientists, in other concepts that require a ‘faith’ of sorts – such as dark matter / dark energy / the graviton / the Higgs Boson, etc.

        Should we stop considering probability and intuition? Not at all – these inform us in lots of ways and guide our efforts & research.

        In short – the lack of data proves nothing, one way or the other – so I’m not sure why you’re jumping all over everyone who expresses an opinion about the *wider* topic discussed here – rather than sticking purely to the implications of the Bayesian analysis itself.

      • SJStar says:

        Eh? What? I think and said the exact opposite of this..

      • Jon Souter says:

        I’m not sure what you’re saying, as you don’t ever really give a good or thorough account of your argument – instead just seeming to rant at people for being wrong, or failing to understand.

        I think you’ll find many of the people you’ve flamed fully understood the article, but then simply moved on to discuss side issues and their own feelings around this broad and fascinating subject, in a more generalised way.

      • SJStar says:

        You may have a point. I have been focussing on the central issue that people blindly think that life already exists in the universe. It doesn’t.
        I see it as another example of the rise of the anti-science movement, where anyone feels they can make a comment and imagine that it is of equal value to someone who has been trained and behaves as scientists should. (These are the same people who attack climate scientists.)
        The comments here really annoyed me. Instead of pausing a thing of the implications of what is being said, the commentary swings to just reject it. I disagree that “the people you’ve flamed fully understood the article”.

        There are time to come up to the plate. This is one of them.

    • bfmorris says:

      “To think we are the only biological sentient entities in the Universe is utterly retarded.”

      Therefore it follows that thinking there is only one arthur_gould in the universe is as utterly retarded as well?

  12. Brad351 says:

    Time and time again it has been proven that many aspects of our existance are not unique. Starting with the fuzzy nebulae that became galaxies just like the one we live in, continuing through the discovery that planets around other stars are not rare at all. That evidence of small rocky planets can now be seen by our most advanced scopes shows they too are not unique. I’m quite certain that we will eventually extend our family of facts to include planets with liquid water on their surface, atmospheres with the chemical signatures of life, if not life itself frozen on some asteroid or local planet. I most certainly prefer MY universe to be a glass half full. Your analysis is interesting… in a navelgazing kind of way. But what it really says is something that most of us already know: That the chances of encountering intelligent life during the span of our civilisation are vanishingly small.

  13. MD Nealy says:

    the idea that life has or could arise in an another Earth-like environment has only a small amount of supporting evidence, most of it extrapolated from what is known about abiogenesis, or the emergence of life, on early Earth

    The problem with that quote is we really don’t know much about abiogenesis. It seems rather disingenuous to throw that out there as evidence.

  14. squidgeny says:

    A lot of commenters here seem to be completely misreading the article.

    The scientists aren’t saying aliens don’t exist, or that they’re highly unlikely – they’re saying we have insufficient evidence to reach a conclusion either way. They’re criticizing the unscientific (yet completely human) optimism of others.

  15. lcrowell says:

    In connection with a study I did on solar system stability and the stability of extra-solar systems I did a Bayesian analysis with existing data to estimate the probability extra-solar systems might have a planet in an orbital configuration similar to Earth. I estimate there might be about 1000 such planets similar to Earth in our galaxy. This has some connection to the question of life in the universe. I suspect some subset of these planets may host complex life similar to what is seen here.

    The question before us is whether simple life is fairly generic. Suppose the probabilities for life occurring on a planet with conditions sufficiently similar to the early Earth are approximately equal, the joint probability (posterior probability) is sufficient to say the probability for life occurring on a wide range of probability may be bounded considerably above zero. This can only be determined by direct data, such as whether there is some life form in subterranean conditions of Mars, or in the geysers of Enceladus. If these outcomes obtain we may then be able to say that life is a fairly abundant property in the universe and that maybe a decent number of those ~1000 planets have complex eco-systems of life comparable to Earth. If we find no life on Mars and Enceladus, we may then not be able to draw this statistical inference.

    The prospects for ETI on other planets sufficiently close for detection is I think very low. I suspect the SETI program will only set lower bounds on the probability for intelligent life in the universe.

    LC

  16. Typhon1 says:

    Absence of evidence is not evidence of absence. These articles always stoke up the nay-sayers to screeching point. “No, no, no. There can’t be any life out there, there ISN’T any life out there. We haven’t detected it so far ergo it doesn’t exist”. They avoid the fact that we’ve only been actively trying for a few short years. Some try wrapping it up in fancy high sounding words, phrases and abstruse mathematics to prove we’re alone but in the end they have absolutely no idea. On the other hand how can anyone claim to be a xenobiologist? What, pray tell, do they study? But of course everyone is a bloody expert aren’t they and nobody likes to think that they may be in the dark.

    • SJStar says:

      “These articles always stoke up the nay-sayers to screeching point. “No, no, no. There can’t be any life out there, there ISN’T any life out there. We haven’t detected it so far ergo it doesn’t exist”

      To the contrary, no one is saying that at all!

      There is an absence of PROOF, but there is no absence of scientists (or people) looking for that PROOF. (Nor should there be…)

      Ergo. “Absence of evidence is not evidence of absence. ” Is quite irrelevant!

      Again read what the article truly says and is implying!! Please!

      • SJStar says:

        To quote an independent Wikipedia;

        You mean astrobiology NOT xenobiology.

        “Astrobiology concerns itself with interpretation of existing scientific data; given more detailed and reliable data from other parts of the universe, the roots of astrobiology itself—physics, chemistry and biology—may have their theoretical bases challenged. Although speculation is entertained to give context, astrobiology concerns itself primarily with hypotheses that fit firmly into existing scientific theories.”

        Xenobilogy pertains to;

        “…xenobiology has come to be used in a more specialized sense, to mean “biology based on foreign chemistry”, whether of extraterrestrial or terrestrial (possibly synthetic) origin. Since alternate chemistry analogs to some life-processes have been created in the laboratory, xenobiology can be said to be an extant subject.”

        None of the authors of this paper or story pertain to xenobiology. Just saying…

      • Typhon1 says:

        I know there’s no proof! I said that because there’s no proof the usual suspects therefore say life isn’t out there! It doesn’t mean life doesn’t exist elsewhere. Read what I wrote! Please!

      • SJStar says:

        I have. From this I can only concluded you don’t understand the story nor what people are actually saying here.

        Again, you said “…the nay-sayers to screeching point. There can’t be any life out there, there ISN’T any life out there.”

        Pray tell, who are the “nay-sayers” here who are actually says this??

    • jjbreen says:

      That quote – Absence …. – is getting seriously OLD. Sorry but it is.

      It’s become a too common ‘scape goat’ to try and ‘save face’ and make the other person ‘be quiet’ with a quote that offers NOTHING to the dialog. It is in fact a very empty quote .. that offers nothing. Certainly not for the person spouting it.

      At some point we have to accept the facts and/or the lack of.

      Now does that mean we stop?

      No…

      We do have to move on. Except that as of now – we have no proof of Intelligent Life out there. Sorry, but think about it. Not even SETI has found any signs and not for lack of looking.

      Think about it, we have been sending signals on purpose and not … out there for well over a century now. Now if there was any chance of Intelligent life out there – they too would have been sending on purpose or not – signals out as well, IF they were intelligent.

      But …….

      N A D A – Z I P – Z I L C H …..

      I am 57 years odd. So I grew up with Buck Rogers, Lost In Space, 2001 A Space Odyssey, Star Trek TOS – ALL the Atlas – Gemini – Apollo rocket launches, Star Wars, etc … So I have those very fond memories and such.

      But I read some books that presents a very compelling argument as to why we will not find INTELLIGENT LIFE out there in the likes of Star Trek – Star Wars – etc…. They all presented that the conditions have to be “JUST RIGHT” and all agree it had to be “JUST RIGHT”. One ‘degree’ off and that would have been it – NO LIFE.

      Look at Earth – IF another stray meteor had hit the Earth, it could have KILLED all hopes. If the temperature had been just a slightly too cold or warmer, again – POOF – we would not be here typing on this computer posting this thought.

      No, sometimes the absence of evidence is just that – you have no evidence – you have nothing to support your position except an ‘nice’ little emotional quip that really does not save face and it certainly does not give you any foundation for your ‘facts’ (or lack of).

      It is nothing – nada – zip – just a nice little emotional quip and nothing more. Sorry.

      Yes we will still continue to look and we should. But I feel in the next 100+ years the most we will find – and this too will be significant and very much so – Cellular, Microbial, simple life signs …. and again, that will be significant!

      • Typhon1 says:

        No need to apologise for saying the ‘Absence…’ quote is old. Just because it’s old doesn’t invalidate it. There IS no evidence, yet. I happen to believe, see the word, believe, that there is abundant life throughout the universe but the chances of detecting it directly are slim and meeting it slimmer still until someone develops the Bergholm Drive. Even ‘proving’ that an O2/N2 atmosphere exists on another planet doesn’t necessarily mean life as we know it/think it is there. We may appear to have absence but to suggest there really is absence seems ludicrous. Some of the nay-sayers almost appear to be quasi religious in wanting feel ‘special’ and be the only intelligent beings in the universe. I sometimes wonder if they have any idea how huge the universe is.

      • SJStar says:

        “Just because it’s old doesn’t invalidate it.”

        No it doesn’t, but it is not relevant at all to this paper or story!!
        Actually there IS evidence, but there is not proof!!

        Clearly “believe” is simply nonscientific.

        “We may appear to have absence but to suggest there really is absence seems ludicrous.”
        Another completely specious argument, which is ludicrous in itself!

        “Some of the nay-sayers almost appear to be quasi religious in wanting feel ‘special'”
        – Be more specific. Again, who are the “nay-sayers”??
        (No one here has said what you claim!!)

        – Also ‘feelings’ are irrelevant, as this debate is one evidence and proof. Again, there is no proof!

      • SJStar says:

        Just in case you don’t know the important difference here…

        evidence : the available body of facts or information indicating whether a belief or proposition is true or valid

        proof : argument establishing or helping to establish a fact or the truth of a statement

        There is support of life in the universe (Ie. Us) but there is no actual proof that it exists beyond the Earth.

        Get it?

      • SJStar says:

        Just to conclude this very important point, Spiegel and Turner says in the abstract;

        “Although terrestrial life’s early emergence provides evidence that life might be abundant in the universe if early-Earth-like conditions are common, the evidence is inconclusive and indeed is consistent with an arbitrarily low intrinsic probability of abiogenesis…”

        Note: The title of this article “We Really Hope ET is Out There, But There’s Not Enough Scientific Evidence, Researchers Say” is misleading. They actually don’t say that at all. The title should be something like “We Really Hope ET is Out There, But There’s Not Enough Scientific SUPPORTING Evidence, Researchers Say”

      • Typhon1 says:

        I’ll concede that ‘believe’ is unscientific but then so is “We really ‘hope’ ET …..”. Those who claim there isn’t any life out there ARE being ludicrous. There is neither proof/evidence for or against.

      • SJStar says:

        Sigh. “Those who claim there isn’t any life out there ARE being ludicrous.”

        Ever thought they might be right?

        Please go ahead, and prove me wrong!!!

      • Typhon1 says:

        I’ll concede that ‘believe’ is unscientific but then so is “We really ‘hope’ ET …..”. Those who claim there isn’t any life out there ARE being ludicrous. There is neither proof/evidence for or against.

      • jjbreen says:

        It does not ‘validate’ it either.

        It is an empty and meaningless quote.

        It offers nothing to the dialog. It is nothing more then a seriously empty circular statement. If the quote is the best one has to offer, then it becomes painfully clear, that person has nothing to offer to the dialog. Sorry, but please tell me what it offers?

        As for the “quasi religious” .. no more or less so then your needing to “believe”, if we are honest. Because you “believe that there is …” is well nothing more then “belief” – which is what “quasi religion” is … a “BELIEF”. So all you offer is your “belief” …. right?

      • jjbreen says:

        Okay – I Searched this and came up with everything and anything … but related to Space Exploration – What the heck is a Bergholm Drive?

      • jjbreen says:

        Okay – I Searched this and came up with everything and anything … but related to Space Exploration – What the heck is a Bergholm Drive?

  17. Typhon1 says:

    Absence of evidence is not evidence of absence. These articles always stoke up the nay-sayers to screeching point. “No, no, no. There can’t be any life out there, there ISN’T any life out there. We haven’t detected it so far ergo it doesn’t exist”. They avoid the fact that we’ve only been actively trying for a few short years. Some try wrapping it up in fancy high sounding words, phrases and abstruse mathematics to prove we’re alone but in the end they have absolutely no idea. On the other hand how can anyone claim to be a xenobiologist? What, pray tell, do they study? But of course everyone is a bloody expert aren’t they and nobody likes to think that they may be in the dark.

  18. SJStar says:

    In the linked paper, there are two mentions of published papers with a similar argument.

    The linked paper here says;

    “There are two unpublished works (http://arxiv.org/abs/0807.4969 and http://www.vixra.org/abs/1108.0003), of which we became aware after submission of this paper, that also conclude that early life on Earth does not rule out the possibility that abiogenesis is improbable.”

    * My own bold.

    Note: I also wonder why these last two were not published.

  19. Thomas Houck says:

    Don’t forget the time factor…life elsewhere in the Universe either has existed, does exist or will exist…I believe this to be a fact.

  20. SJStar says:

    In the link I gave earlier, there is a quote by Brendon J. Brewer from his conclusions in his paper “The Implications of the Early Formation of Life on Earth”, that says;

    “…unless there is a direct detection, the answer to the perennial question “are we alone” remains “nobody knows”.”

    Regardless of your point of view, this is the whole point!

  21. Aqua4U says:

    I for one believe that the entire universe is a living thing. Look up and view the body of god! HO!

    There is no doubt that life is everywhere. Unfortunately, most of it is bacterial or microbial and not into quantum mechanics per Se. so I feel in my heart of hearts that we are rare, but not alone…

  22. ToddReece says:

    Well, if life doesn’t exist elsewhere then we are the pinnacle of what the universe can produce…

    Ouch.

  23. tom s says:

    I know there’s life on other planets…I’ve seen too much science fiction to be convinced otherwise.

  24. We should all realize we won’t meet any aliens in our life. Aliens might be in another dimension, one we would never understand and we never knew existed.

Comments are closed.