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New Theory Concludes That the Origin of Life on Earth-Like Planets Is Likely:
Does the existence of life on Earth tell us anything about the probability of abiogenesis — the origin of life from inorganic substances — arising elsewhere? That's a question that has confounded scientists, and anyone else inclined to ponder it, for some time.
A widely accepted argument from Australian-born astrophysicist Brandon Carter argues that the selection effect of our own existence puts constraints on our observation. Since we had to find ourselves on a planet where abiogenesis occurred, then nothing can be inferred about the probability of life elsewhere based on this knowledge alone.
[...] However, a new paper by Daniel Whitmire, a retired astrophysicist who currently teaches mathematics at the U of A, is arguing that Carter used faulty logic. Though Carter's theory has become widely accepted, Whitmire argues that it suffers from what's known as "The Old Evidence Problem" in Bayesian Confirmation Theory, which is used to update a theory or hypothesis in light of new evidence.
[...] As he explains, "One could argue, like Carter, that I exist regardless of whether my conception was hard or easy, and so nothing can be inferred about whether my conception was hard or easy from my existence alone."
In this analogy, "hard" means contraception was used. "Easy" means no contraception was used. In each case, Whitmire assigns values to these propositions.
Whitmire continues, "However, my existence is old evidence and must be treated as such. When this is done the conclusion is that it is much more probable that my conception was easy. In the abiogenesis case of interest, it's the same thing. The existence of life on Earth is old evidence and just like in the conception analogy the probability that abiogenesis is easy is much more probable."
Journal Reference:
Daniel P. Whitmire. Abiogenesis: the Carter argument reconsidered [open], Int J Astrobio, 2022. DOI: 10.1017/S1473550422000350
(Score: 3, Funny) by Runaway1956 on Wednesday October 05 2022, @06:27AM (1 child)
Life made earth earth-like, so yeah, if you find an earth-like planet, you're going to find life.
"Taxi, take me to the night life!"
"Sure Boss, I'll just look for free oxygen floating around!"
(Score: 3, Informative) by Immerman on Wednesday October 05 2022, @03:32PM
Mercury, Venus, and Mars are all regarded as Earth-like planets.
In astronomy "Earth-like" doesn't refer to anything life has done. Instead it means more geological composition - a rocky world rather than a gas-giant or ice ball.
Oxygen though is indeed considered likely evidence that an Earth-like planet contains life. Not because it's necessary (Life thrived on Earth for billions of years without it), but because there's not a lot of other ways to produce free oxygen over geologic time scales so that it can build up in the atmosphere. Free oxygen is so reactive that environmental oxidation will tend to rapidly strip it from the atmosphere unless large volumes are being produced continuously.
(Score: 5, Informative) by maxwell demon on Wednesday October 05 2022, @06:50AM (11 children)
We have exactly one data point about that question. Any conclusions about probability are on shaky ground here. All we can say is that the probability has to be non-zero (assuming there is only a finite, though possibly large, number of earth-like planets).
The Tao of math: The numbers you can count are not the real numbers.
(Score: 5, Interesting) by maxwell demon on Wednesday October 05 2022, @07:09AM (8 children)
Another point: The analogy he makes here is not correct, because unlike in the case of contraception, we do not know what affects the probability of life on an earth-like planet.
For example, earth has an unusually large moon. We don't know if that plays a role in developing life. But given that the only planet we know of that has life has an unusually large moon, using his own argumentation we should conclude that it is highly likely that a large moon is important for having life. But then, other earth-like planets are unlikely to have unusually large moons (that's what "unusually" means). Which would then hint at life on earth-like planets being unlikely (because a likely precondition is unlikely to be fulfilled).
The Tao of math: The numbers you can count are not the real numbers.
(Score: 3, Interesting) by bzipitidoo on Wednesday October 05 2022, @02:40PM (2 children)
We like to think we're special. I think that blinds us. Centuries ago, there was dogma that the Earth was the Center of the Universe, backed by threats to burn at the stake anyone who dared disagree.
One of the most interesting findings by the pioneers of CS is how shockingly little it takes to make a Turing complete machine. Just one kind of logic gate, or a cellular automata with one really simple rule, is enough. Supposing that life takes little more than that, I would therefore guess life in the universe is fairly common.
I would further guess that microbial life is far and away the most common, and that the biggest barriers to intelligent life is not life, but intelligence. It took billions of years for Earthly life to advance from mindless bacteria to multicellular life with brains, then another half a billion years for those brains to get smart enough to build a civilization. How inevitable such a progression is, is really hard to say. Will that almost always happen, given enough time? Or maybe, the universe is a little too harsh, and most life is destroyed before it can evolve intelligence. Life that evolves on a planet orbiting the wrong kind of star is screwed. Massive stars burn out quickly. The other extreme, red dwarfs, it seems they may be prone to life destroying flaring. Stars too close to the center of a galaxy may also be in a too harsh environment, with huge amounts of cosmic radiation ensuring life can't ever get started.
The moon is a most interesting variable. If that is necessary, to stabilize a planet and thereby give life a steadier platform on which to live, then that would make life a lot rarer.
(Score: 0) by Anonymous Coward on Wednesday October 05 2022, @04:26PM
Yep. The big step isn't biogenesis, that happened within a max of 200 million years after the planet was technically cool enough. The big step was from single cell to multicellular. That took 3 billion years.
(Score: 2) by mcgrew on Wednesday October 05 2022, @06:53PM
We like to think we're special. I think that blinds us. Centuries ago, there was dogma that the Earth was the Center of the Universe, backed by threats to burn at the stake anyone who dared disagree.
That statement argues against itself. If we though we were special, nobody would have been burned at the stake because even Galileo wouldn't have believed his own eyes.
One of the most interesting findings by the pioneers of CS is how shockingly little it takes to make a Turing complete machine.
That's offtopic, we're talking about life, not technology. If you know anything at all about how computers actually work you know they can't think. Before the late 1800s people would have been shocked to learn how easy it is to turn electricity into light. There's no difference between these two apples, your apple doesn't match your orange.
I would further guess that microbial life is far and away the most common, and that the biggest barriers to intelligent life is not life, but intelligence.
Now, that's not only 2+2 logical, but the single example of life we have here backs it up.
. Life that evolves on a planet orbiting the wrong kind of star is screwed.
Life will never start in a stellar system like that.
The moon is a most interesting variable. If that is necessary, to stabilize a planet and thereby give life a steadier platform on which to live, then that would make life a lot rarer.
Rather than stabilizing the planet, it makes it wobble and its tides stir the ocean waters. That is likely necessary for life to begin anywhere, but then, it could start in a place like Europa, a large satellite with planetary tides. In fact, I think if we find no life there, we're unlikely to find it anywhere.
But the fact is, we're clueless. Doesn't stop me and others from writing fiction about it, look at how closely this story [baen.com] written in 1946, the year the first computer was patented, describes the internet (except his internet was censored like everything was in 1946 and a manufacturing defect removed the censorship and caused the problems).
I'll bet he didn't believe for a minute how his story would loosely mirror his future, our presebt.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by Immerman on Wednesday October 05 2022, @04:16PM (4 children)
I think you're misunderstanding the argument.
The accepted wisdom is that since we have only a single data point, we can't conclude anything about the likelihood of life arising on Earth-like worlds.
His counterargument is that since we exist, we can infer that it was *probably* easy for life to arise here. Simply because if you look at all the (presumably numerous, potentially infinite) intelligent species in the vastness of the universe, most of them would have arose from worlds where it was easy for life to arise. So pick one species at random (us), and they'll probably be from somewhere where it was easy for life to arise. And that is true regardless of the probabilities involved, except in the extreme case where life is more likely to arise on "hard" planets than "easy" planets are to exist.
Now, you are correct that maybe things like our unusual moon is one of the things that made it easier, so we can't automatically assume that all Earth-like worlds are "easy" for life. However, making such assumptions without evidence because of a merely plausible hypothesis is poor scientific form.
Moreover, even if large tides are important for maintaining volcanic activity to feed early protolife, Earth-like moons around gas giants get similar tidal benefits, and judging by our solar system are likely far more common than Earth-like planets - we have over a dozen, at least two of which, Europa and Titan, look incredibly promising for life.
We also don't really know just how unusual our moon is - we've only got our own solar system for reference. We can barely detect Earth-like planets around other stars, moons are still far too small to detect.
And for that matter we don't even know how unusual life is within our own solar system - we've yet to really look for it. And the preliminary searches we *have* done keep hinting that life may actually be quite common - the few tests for life on Mars have all come back positive (though we've come up with alternate explanations that render those results inconclusive), and we've spotted some promising gasses in Venus's atmosphere as well.
Of course, panspermia within a solar system is actually fairly plausible, so we might find life throughout the solar system, all distantly related to us - in which case we can't assume that life actually arose on Earth. Mars is speculated to have been a warm, wet world back when Earth's surface was only beginning to cool enough for water to exist. And the various gas giant moons may have cooled enough even sooner than that. The fact that life was present on Earth almost as soon as liquid water existed hints that either life can arise very easily, or it arrived here from somewhere else.
Alternately, if we find any life that's NOT related to us (e.g. not DNA based), then that would strongly suggest that life can arise very easily, and the galaxy is probably jam-packed with it.
(Score: 2) by maxwell demon on Wednesday October 05 2022, @05:20PM (3 children)
And my argument is that this counterargument is wrong.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by Immerman on Wednesday October 05 2022, @08:11PM (2 children)
You just repeated my point with different words.
There were never any probabilities attached to "easy" - only that it's easier than "hard", so relabeling them as "very unlikely" and "extremely unlikely" changes nothing.
We know little about *how* easy it was for life to arise here, but we do know that it probably *was* easy, compared to most places.
And given that, it seems reasonable to assume that most planets like ours were similarly "easy" for life to get started on - whatever that means. A big moon is really the only characteristic Earth has that we don't have reason to believe are also common elsewhere. (And we have only very limited evidence from which to conclude that it might be rare)
Meanwhile - we know that life not only arose here, it did so almost as soon as liquid water existed on the surface. Which strongly hints that either it was *very* easy to life to start here, or it originated elsewhere.
Basically - if the odds of life arising are equivalent to rolling a die to get a million 1's in a row - then it *might* happen within the first million throws, but it's far more likely to require countless trillions of throws before it happens. And the safe bet is that it took a fairly "typical" number of throws in our case.
(Score: 2) by maxwell demon on Thursday October 06 2022, @04:46AM (1 child)
So you're trying to get out by redefining words? Sorry, "easy" has a meaning. And that meaning is not "all other options are even harder."
And the point remains that we can't say anything about the probability of finding life on other planets, which was Carter's point. We still can't tell because we don't know the probability life had on earth. So even in the unlikely case that Whitmire really meant it in the way you are now claiming, he's still wrong in telling Carter wrong, just for different reasons.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by Immerman on Thursday October 06 2022, @01:52PM
"Easy" and "hard" are a inherently relative concepts that can easily both be applied to the same task based on context:
To someone playing in a sandbox, moving a few dozen more cubic yards of sand is hard, while to someone operating a river dredge, it's so easy it's barely worth mentioning.
An "easy" Olympic figure skating performance is going to be nearly impossible for most skaters.
And when it comes to creating life - "easy" and "hard" are likely to mean very different things that they do for making bread.
(Score: 2) by Thexalon on Wednesday October 05 2022, @04:58PM (1 child)
Not exactly: We have, for instance, some evidence of potential organic chemistry having happened on Mars and Venus.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 3, Touché) by Immerman on Wednesday October 05 2022, @08:16PM
Hints are not data points.
Until we can conclusively state that Mars either did or did not harbor life, any such hints are only relevant to encouraging more conclusive studies, NOT to estimating the probability.
For that matter though, we haven't even established that the Moon doesn't harbor life, much less any of the other planets. We really do only have exactly one data point from which to extrapolate, and it's positive. All we can say about the rest of the solar system is that any life present isn't super obvious.
(Score: 2, Touché) by Opportunist on Wednesday October 05 2022, @08:00AM
Not every harebrained idea someone brushed out of his neckbeard after getting up deserves being called a theory.
(Score: 2) by inertnet on Wednesday October 05 2022, @09:04AM (5 children)
An interesting Cool Worlds video [youtube.com] by professor David Kipping on the subject.
(Score: 2) by mcgrew on Wednesday October 05 2022, @06:57PM (4 children)
If it's a talking head I'm not interested. I can read ten times faster than he can talk, unless he's a auctioneer, and if he is I wouldn't understand him. Facebook is for showing, not telling.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by inertnet on Wednesday October 05 2022, @08:31PM (3 children)
He usually explains his own or other people's scientific work on astrology, exoplanets and such. Not just a talking head, he visualizes the things he's explaining.
(Score: 3, Touché) by DannyB on Wednesday October 05 2022, @08:56PM (2 children)
What if I find astrology unconvincing?
To transfer files: right-click on file, pick Copy. Unplug mouse, plug into other computer. Right-click paste.
(Score: 2) by inertnet on Wednesday October 05 2022, @10:07PM (1 child)
Sorry, astronomy. Astrology has nothing to do with science, but I tend to mix up those words.
(Score: 2) by DannyB on Thursday October 06 2022, @07:19PM
Mixing them up makes sense because of the "logy" suffix witch means "science of" or "study of".
Anthropology
Biology
Epidemiology
Epistemology
Geology
Meteorology
Microbiology
Pharmacology
Proctology
It is unfortunate that the term Astrology became attached to something so bogus as the planets affecting our lives. (unless they are on a collision course with the Earth.)
To transfer files: right-click on file, pick Copy. Unplug mouse, plug into other computer. Right-click paste.
(Score: 2, Interesting) by khallow on Wednesday October 05 2022, @11:26AM (5 children)
Sorry, that's broken. First, you can't "assign values". There's only two relevant values to that mutually exclusive conception example - one scenario is true and the other false. There is no room for assignment of probability values and neither scenario is at all changed by old evidence. In order to have the ability to assign values as he does, you implicitly have additional evidence. And well, the additional evidence is what is shaping the probabilities not the old evidence.
What's particularly bizarre about the paper is that the treatment of old evidence has traditionally been that it doesn't distinguish between hypotheses that are compatible with the old evidence - the very opposite of the stance he is taking here. For example, if you have alternative plausible theoretical explanations for Mercury's precession than General Relativity, then those are just as valid until you come up with new evidence. Assignment of probability values is futile because the old evidence doesn't distinguish between these rival theories.
(Score: 2) by bart9h on Wednesday October 05 2022, @05:06PM (4 children)
I haven't read TFA, but TFS smells like BS.
The best origin-of-life theory I have came across is on the book The Vital Question [wikipedia.org], by Nick Lane. I highly recommend it.
(Score: 2) by mcgrew on Wednesday October 05 2022, @06:59PM
I did read TFA, and it is also hand waving and calling an untestable hypothesis a "theory". It's no more valid than Pizzagate, except that Pizzagate was easy to debunk.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by Immerman on Wednesday October 05 2022, @08:24PM (2 children)
Does he offer any interesting insights? From the Wikipedia page it looks like he just makes some descriptions of how life works today, along with some references to the hydrothermal vent origin theory which was already going mainstream at least a decade or two before before publication.
Presumably he tied it together with a nice "I don't speak science" bow to become popular, but does he offer anything of interest to people who *do* speak science?
(Score: 2) by bart9h on Thursday October 06 2022, @08:10PM (1 child)
Yes, he does.
The book is not light on science. I had a hard time following it.
(Score: 2) by Immerman on Friday October 07 2022, @04:03AM
Cool
(Score: 3, Interesting) by oumuamua on Wednesday October 05 2022, @01:35PM (17 children)
Life on Earth emerged, literally, just after the molten ball cooled off. Molten ball: 4.5 billion years ago, life emerges: 3.7 billion .
https://naturalhistory.si.edu/education/teaching-resources/life-science/early-life-earth-animal-origins [si.edu]
If abiogenesis was difficult, you'd expect life to show up billions of years after ideal conditions appeared.
It is like someone making a half court basketball shot on their first try.
(Score: 0) by Anonymous Coward on Wednesday October 05 2022, @01:56PM
Well, put even more simply, it is thermodynamically favorable. Therefore it happens everywhere all the time, as certain as planets revolving around stars.
(Score: 3, Interesting) by mcgrew on Wednesday October 05 2022, @07:06PM (10 children)
Those were almost certainly the conditions necessary. Note that as far as is known, life only began on Earth then and never afterwards. My question is, how old did the universe have to be for the right stars to go supernova to produce the nevessary elements that fused into various substances that are necessary for life?
mcgrewbooks.com mcgrew.info nooze.org
(Score: 3, Interesting) by Immerman on Wednesday October 05 2022, @08:32PM (5 children)
As far as we know, there's absolutely no reason to expect later-spawning life to survive. New life could be spawning every day on Earth, but it would have no chance to survive in competition with life that's already been optimized by billions of years of evolution.
And that'd be just as true after a thousand years of evolution. The only way a new form of protolife that just barely figured out imperfect self replication could compete with life that's been around for a while is if it had a *huge* innate advantage. And if it had such a dramatic advantage, then it would be reasonably expected to rapidly outcompete all pre-existing life once it had time to start evolving a few improvements. Resulting in exactly the same fossil record as if life had only arisen once.
(Score: 2) by mcgrew on Thursday October 06 2022, @04:07PM (4 children)
There was a billion years of life on Earth before evolution started 750 million years ago.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by Immerman on Thursday October 06 2022, @04:34PM (3 children)
What?
The first (definite) animals evolved around 750M years ago, but evolution started immediately after the first self-replicating pre-biotic systems started replicating 4+ billion years ago.
There's nothing magical or animal-specific about evolution - it's just the inevitable result of imperfect replication and death due to environmental factors.
(Score: 2) by mcgrew on Tuesday October 11 2022, @06:04PM (2 children)
Not according to that scientist, who studies ancient organisms. Life began, according to her, one billion seven hundred fifty years ago and didn't start evolving until life had been here for a billion years. Note by "life" it's not viruses, which aren't really alive, since they need a host to replicate. Oh, and if it's not alive it can't die, even if, like an automobile, it can seem to be alive ("it's dead, Jim." "Well, hold on... try it now).
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by mcgrew on Tuesday October 11 2022, @06:26PM (1 child)
Correction: one billion seven hundred fifty MILLION years.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by Immerman on Tuesday October 11 2022, @08:57PM
Citation?
Here's one of mine, with a links to many others: https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life [wikipedia.org]
If one scientist says something, they're probably wrong. Something like 80-90% of all published studies are later disproven - that's the whole point of peer review. And why you should take everything with a grain of salt until a concsensus of scientists agrees that something is true after it has withstood extensive challenges by experts in related fields.
(Score: 3, Interesting) by Immerman on Thursday October 06 2022, @05:16PM (3 children)
As to how old the universe had to be for life to form? First off, we can only talk about life-as-we-know-it - but that's built entirely out of light elements, so it could theoretically have formed as soon as the light elements were present in the universe, shortly after the first stars exploded at least 13 billion years ago.
The first generation of stars were formed from pure hydrogen (and possibly a bit of helium), somewhere between 100 and 400 million years after the big bang which was all that existed in the early universe. Fusion in their cores created lighter elements up to at least oxygen (the C-N-O cycle being the tail end of stellar fusion, though there's probably lots of incidental production of heavier elements), and the heavier elements (including the transuranics) were created in their death-explosions, which mostly happened a few million to a few hundred million years after the big bang for all the giant and hyper-giant stars. Even the smaller stars
The second generation stars formed from their remnants, and their dust clouds would have contained all the elements necessary to form rocky planets and life, though possibly not in great enough concentrations for either to be common. (Their spectral lines show their atmosphere is less than 0.1% "impurities" - aka everything heavier than helium). They produced even more light elements, and their death explosions created even more heavy elements.
Our sun, along with most visible stars, is a third generation star, whose atmosphere contains ~1% impurities, and whose pre-stellar dust cloud contained plenty of raw materials to produce rocky planets and life. They started forming about 9 billion years ago, while our own is about 4.5 billion years old (with Earth, and earth-born life forming within the next 500 million years).
So 9 billion years ago is probably a good ballpark guess as to when the probability of life forming on new planets reached approximately the level it would have been at when our sun formed.
The Fermi paradox exists because of the fact that millions if not billions of Earthlike planets in our galaxy were already as old as Earth is now before Earth even formed, and there's likely hundreds of billion more that formed in the billions of years in between.
(Score: 2) by Immerman on Thursday October 06 2022, @05:21PM
Bah - I hate catching editing errors after hitting submit.
>and the heavier elements (including the transuranics) were created in their death-explosions, which mostly happened a few million to a few hundred million years after the big bang for all the giant and hyper-giant stars. Even the smaller stars
Should be
>and the heavier elements (including the transuranics) were created in their death-explosions, which mostly happened a few million to a few hundred million years after their formation for all the giant and hyper-giant stars. Even the smaller stars were free of impurities, and thus would have burnt much hotter and faster than modern stars
(Score: 2) by mcgrew on Tuesday October 11 2022, @05:58PM (1 child)
Boron, Cadmium, Copper, iron... how old was the universe when these were produced? If it was 7 billion years ago, we could be the first, life on Earth started one billion seven hundred fifty million years ago, the sun about two or three billion when the Earth formed. You need the sun and the Earth for Earthian life to start.
mcgrewbooks.com mcgrew.info nooze.org
(Score: 2) by Immerman on Tuesday October 11 2022, @08:41PM
I just gave you the timeline. When the first generation hypergiants started exploding is when the first *everything* became available - from lithium to uranium and beyond. About 100M years after the big bang, or 13.7 billion years ago. But the amounts were pretty low.
Third-generation stars like ours, whose planet systems probably have element ratios similar to our own, started forming about 9 billion years ago, though the concentrations of heavier elements might not be quite as high as here, depending on the specifics of the protostellar cloud formation.
Where are you getting your numbers from?
Life started on Earth at least 3.42 billion years ago - the age of the oldest fossils, and it's suspected that the last common ancestor of all Earth (LUCA) life actually lived between 3.71 and 4.41 billion years ago - as early as a hundred million years of the formation of Earth, and about the same time liquid water began to form. https://en.wikipedia.org/wiki/Timeline_of_the_evolutionary_history_of_life [wikipedia.org]
Meanwhile, the sun is roughly the same age as the Earth and other planets, between 4.5 and 4.6 billion years old. Planets form from the same protostellar cloud as their suns, and once the sun ignites most of the remaining cloud is blown away by the photon pressure. Though the gas giants may have caught much of it as it blew out past them - the process likely took several million years.
https://en.wikipedia.org/wiki/Sun#Formation [wikipedia.org]
https://www.worldatlas.com/articles/how-old-is-the-sun.html [worldatlas.com]
(Score: 2) by captain normal on Wednesday October 05 2022, @08:54PM
Well there's a 100 billion first shots just in our galaxy.
When life isn't going right, go left.
(Score: 2) by legont on Thursday October 06 2022, @01:56AM (3 children)
Life did not emerge. It simply came here from somewhere else.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 2) by Immerman on Thursday October 06 2022, @05:46PM (2 children)
And when did it emerge there?
(Score: 2) by legont on Friday October 07 2022, @12:25AM (1 child)
Perhaps, even before the big bang.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 2) by Immerman on Friday October 07 2022, @03:44AM
Not unless it's high tech enough to have hopped into the universe from elsewhere hundreds of millions of years after the big bang - prior to that the universe was too hot for atoms to exist. And if you're hopping universes, then you run into the problem that there's absolutely no reason to believe the laws of physics are the same between any two universes. It's quite possible that out of an infinite number of universes, this is the only one in which atoms as we know them can exist. Kind of hard to colonize another universe when your constituent atoms cease to exist upon entering.
And even assuming it's possible - all your insanely magi-science equipped universe-hopping aliens have accomplished, from our perspective, is to push the origins of life back a little. At some point in the past life had to emerge from somewhere - unless you want to argue that life somehow predates not just our universe, but all of existence? And... that's a bit of a problem, as it certainly seems that life has its roots in physical reality.
(Score: 3, Informative) by mcgrew on Wednesday October 05 2022, @06:30PM (1 child)
Why is this incredibly weak hypothesis being called a theory? From TFA:
At best, he argued, the knowledge of life on Earth is of neutral value. Another way of looking at it is that Earth can’t be considered a typical Earth-like planet because it hasn’t been selected at random from the set of all Earth-like planets.
Not random? Am I dim today or is the author not communicating well?
As I've said before, until we have a clue about HOW abiogenesis started, and what conditions were necessary to to start, we will remain clueless about how numerous, scarce, or nonexistent life is outside our solar system. Fictional examples:
http://mcgrewbooks.com/Voyage/Contact.html [mcgrewbooks.com]
https://www.mit.edu/people/dpolicar/writing/prose/text/thinkingMeat.html [mit.edu]
mcgrewbooks.com mcgrew.info nooze.org
(Score: 3, Informative) by Immerman on Thursday October 06 2022, @02:14PM
Any data source pre-screened by any selection criteria is no longer truly random, and thus can't be assumed to be at all representative of the larger population.
For example: if you perform a random phone survey you'll find that roughly 100% of people own phones, even if only 1% actually do. That's one of the reasons that online surveys are generally regarded as unsuitable for most scientific purposes - you're pre-screening your sample population to include only those people from the target population that have internet access, visit someplace your survey is advertised, and are inclined to take online surveys - a subset that is extremely unlikely to be a representative sample of the larger population.
Similarly, if you survey a bunch of Earth-like planets with life on them (or just one) they tell you nothing about Earth-like planets in general, only about the pre-screened subset of Earth-like planets with life. Or in our case, specifically Earthlike planets that gave rise to intelligent, technological societies - which may be very atypical even among life-bearing worlds.
And since we can look around and see three other Earth-like planets (and over a dozen Earth-like moons) in our solar system that have no (obvious) life on them, we can be fairly confident in saying that Earth's vibrant ecology is NOT typical of Earth-like plant(oid)s.
(Score: 2) by SomeRandomGeek on Wednesday October 05 2022, @10:43PM (1 child)
Humans just seem pathologically incapable of saying "There is not enough evidence to reach a conclusion. Therefore, I don't know." Everybody, even people that should know better, people with scientific training, seems to say "There is not enough evidence to reach a conclusion. Therefore, here is my best guess." And then they proceed to act as if that guess is worth more than a bucket of warm piss. It is not. When you don't have enough evidence to know, embrace not knowing. Don't be seduced by the guess.
(Score: 2) by Immerman on Thursday October 06 2022, @02:37PM
>"There is not enough evidence to reach a conclusion. Therefore, here is my best guess." And then they proceed to act as if that guess is worth more than a bucket of warm piss.
You realize that's basically step one of almost all real-world scientific inquiry?
Step two is rigorously studying and expanding on the logical implications of your guess until you come up with something you can perform an experiment to test that will give different results than if the commonly accepted wisdom is true.
Step three is actually building and performing the experiment to find out if your guess was correct. To *generate* the evidence needed to reach a conclusion.
Step four is to publish and thoroughly examine the results of both your logic and experiments, looking for any flaws in either that could deliver the results you got despite your hypothesis being (in)correct.
Though usually the publishing bit only happens if your results confirm your guess, to the lament of a great many scientists. Among other things it means that the next person to make the same guess has to unknowingly replicate all your work rather than just looking up your results. But between ego and journals that are far more interested in positive results, that's the current reality.
(Score: 2) by legont on Thursday October 06 2022, @02:09AM (4 children)
There is exactly zero evidence that life emerged on earth. Meantime, if our rock were to be hit by another similar sized rock, our life would be spread all over the galaxy.
More than that, we probably came from space multiple times. We are too weak to walk on this planet and our skin can't take too bright Sun. Much more common little rock near a red dwarf is our birth place.
Lastly, Bible gives a rather interesting cosmology story starting with Big Bang and all the way to Noah.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 3, Interesting) by Immerman on Thursday October 06 2022, @03:08PM (2 children)
No direct evidence, but plenty of supporting hints in the form of various experiments suggesting the pre-biotic building blocks were likely all present on early Earth, along with plenty of environments conductive to self-organization into pre-biotic forms.
Meanwhile, Occam's razor comes down firmly on the side of abiogenesis occurring here. There's really only two options: either it occurred here, or it occurred elsewhere and managed to survive the intense heat and pressure of two independent asteroid impacts separated by months or decades drifting in interplanetary space. Well, I suppose there's also option three - intelligent aliens visited and either intentionally or accidentally introduced some early microbes (the "alien spaceship sewage dump" theory), but in the absence of any direct evidence, intelligent intervention is generally regarded as stretching Occam's razor to the breaking point.
Panspermia seems at least moderately possible within a solar system - rock structure could conceivably shelter pockets within it from the insane temperatures and pressures of impact, and we know at least some microbes can survive months or years in space with no more protection than the Earth's magnetic field - the inside of an asteroid should be survivable.
Between stars though is much less plausible for two big reasons. First is the impact violence - solar escape velocity is several times greater than planetary, meaning both asteroid impacts are going to be a minimum of dozens of times more violent, making it much less likely that anything would survive.
Second, the distance between stars is so great that any life would have to survive at least millions of years (assuming a direct trajectory to the nearest star) of drifting through interstellar space at temperatures close to absolute zero. Over those timescales, even deep within the asteroid, just the ambient radiation from the surrounding rock is going to completely shred any DNA, and at cryogenic temperatures even something like tardigrades with their incredible DNA repair skills is going to be completely inert, so no repairs can occur.
So, basically, for interstellar panspermia you need either an incredibly contrived asteroid that's sturdy enough to not be liquified by impacts at interstellar speeds, and radioactive enough to keep a colony of radiation-resistant chemovores warm and healthy... or an alien space ship. In that scenario, the space ship actually starts looking like the more plausible option.
(Score: 2) by legont on Friday October 07 2022, @12:36AM (1 child)
Once again, there is no evidence life emerged here while all the building blocks of life are likely presented in comet's ice.
As per surviving space and time, when a celestial body breaks for whatever reasons, there are small chunks and big ones. Big enough to protect life inside for indefinite time.
Finally, folks who lived before the big bang and wanted to survive it, likely took some measures.
Anyway, my original point was that there was not enough time for life to emerge here. The probability is just too low. See, we can't even do it on purpose.
"Wealth is the relentless enemy of understanding" - John Kenneth Galbraith.
(Score: 2) by Immerman on Friday October 07 2022, @03:32AM
If solid rock liquefies on impact because of the energy, or is subjected to enough temperature and pressures to convert carbon into rare forms of diamonds, then it can't protect anything. And that tends to happen even with normal asteroid strikes, much less those involving interstellar speeds. But yeah, it's not *impossible*
Crossing interstellar distances though? And all the radiation shielding in the world won't protect you from the radiation produced by the shielding itself. Carbon, potassium, etc. - pretty much *everything* is at least slightly radioactive, and that radiation will destroy any living thing in suspended animation for millions of years. It has to be alive and active to repair the damage, which requires an extremely contrived environment when in interstellar space, where ambient temperatures are cold enough to freeze hydrogen.
>there was not enough time for life to emerge here. The probability is just too low.
Since we know almost nothing about the actual probabilities, and have a window of hundreds of millions of years to work with, that seems like a completely unsubstantiated statement.
>See, we can't even do it on purpose.
Have we tried? We certainly haven't dedicated a planet-sized laboratory to the project for hundreds of millions of years - as was available on early Earth. "We can't do it" is a horrible argument for claiming "it can't be done". Especially when talking about a field where we're only just beginning to reach the level of making crude finger paintings. We still know almost nothing about biology.
(Score: 2) by Immerman on Friday October 07 2022, @03:55AM
Also, a correction - If Earth was hit by another similar sized rock, all the debris would remain within our solar system as it wouldn't be going fast enough to escape - unless the thing that hit us came from interstellar space - in which case the Earth would likely be liquefied if not vaporized by the incredible energies involved, reaching temperatures far too hot for life to survive (if you're boiling iron, nothing chemically active at water temperatures could survive)
A small asteroid at interstellar speeds could conceivably knock debris out of the solar system without liquefying the planet - but most of the asteroid and ejecta would still be heated to thousands of degrees. Life would have to be *insanely* lucky to survive that in some protected bit of debris that somehow didn't get hot enough to melt.