There are so many potential reasons why life would be incapable of existing on a planet in the "Goldilocks Zone" that we can't even fathom. It could even come down to something as simple as the infinite potential variations in elemental composition for a given planet. Not to mention the sheer enormity of time required for something like abiogenesis to occur and those forms of life to evolve into something we could actually discover, even when the conditions are suitable.
We can't calculate those odds. We can't even start. It's like trying to calculate the likelihood that future AI will destroy humanity. We just can't know because it's so deeply theoretical.
For that reason, it seems absolutely absurd to me that someone would say with certainty that life exists elsewhere in the universe. We just can't know. The unlikelihood of its existence could be infinitely high and we might just be lottery winners. Who knows?
And frankly, I hope we're alone. I really don't want to share the universe. It would be so much nicer just to have it to ourselves. Let us do what we want, wherever we want, without interference until the heat death of everything.
Nobody says with certainty that life exists. But they do say the probability is so high that life in some form exists elsewhere, you might as well be certain.
As for not sharing the universe: what a depressing thought.
Why is that depressing? It's not like we would actually be ALONE. We have each other. We don't need Vulcans or whatever else to keep us company and suck up our resources.
When you put it that way, it doesn't actually matter. There's always going to be someone competing for resources. The only difference is whether they have hands or tentacles.
> For that reason, it seems absolutely absurd to me that someone would say with certainty that life exists elsewhere in the universe.
I'm not sure you have a conception of how truly BIG the universe is. In fact, according to current cosmological evidence, it is infinitely big.
But even if we confine our discussion to our Hubble Sphere, there is almost certainly life elsewhere in the universe. It's just that that life might be very, very far away.
My thoughts too. If we knew there were only 10,000 stars, it could seem likely that the chances of life existing are 1/50,000, and we happen to be lucky. But there are over 100 billion stars in the observable universe.
I think the law of large numbers applies here. The likelihood of life existing being high enough that we are the only ones, but low enough that our existence isn't winning some 1 in a googolplex chance just strikes me as an anthropocentric conceit.
The size of the universe is a large number, but the chance of life just forming from chaos is 1/(a large number). So the odds of life elsewhere in the universe is, roughly, a large number divided by another large number. The question is which large number is larger?
We don't know how difficult it is to create life. The universe is big, but the difficulty of creating life might be much bigger.
Thus. It is not certain that there is life elsewhere.
Just today we found the closest star to us to have a planet in the habitable zone.
The closest star. But, we struggle to observe it in any capacity. Indeed, only today we did. And that's nothing to say of the next closest star, or the next, or the next, ad (nearly) infinitum.
If planets in this zone aren't as rare as we think, life in the universe might also not be as rare as we think.
To me, the question is more "where," rather than "if."
The fact that life appeared on earth very shortly after it formed gives us a good indicator that Abiogenesis may not be that rare.
Something that's probably a lot more rare is favorable conditions over a long time period. It took a long time for life on planet earth to evolve into more complex forms.
I'm pretty sure we're not the only ones out there. But will mankind and our space neighbours exist long enough to facilitate communication?
Is every species that is competitive enough to subdue all other life on its planet doomed to disintegrate due to internal conflict?
Here's one possibility: intelligent life is sufficiently rare yet the universe is sufficiently large that the universe contains a very large number (possibly even an infinite number) of intelligent civilisations, but they are all sufficiently distant from each other in space and/or time that the odds of any of them ever interacting with each other (or even knowing of each others' existence) is extremely low.
e.g. imagine a universe containing a million intelligent civilisations, but each of those intelligent civilisations is in a separate galaxy at least 100 million light years apart. If that is our universe, we might not encounter any of those other civilisations in the next million years. The odds of human extinction could easily be higher than the odds of having any contact with them.
Oh sure it's a particularly human conceit that that number be exactly 1. But it certainly might be that the number is low enough that it will be very very hard for us to ever detect or interact with other life.
the number of stars out there is more like 1,000,000,000,000,000,000,000 pieces, or 1 billion trillion in observable universe. which is just a subset of whole universe. pretty good chances for something out there. hopefully not as xenophobix as humans these days (and more advanced at the same time)
Everyone always says this, but it seems to indicate more of an inability to grasp how much we don't know about other planets on your part than it does my inability to grasp how large the universe might be. It's entirely irrelevant if the universe is infinitely large if the probability of life arising is infinitely small.
If you think psychology is shoddy science wait until you hear some cosmology! The universe is very big so there MUST be life elsewhere. It just can't be otherwise!
Not quite. No one's publishing papers to that effect. What casual science fans and some popular scientists do posit is that the universe is so big, our solar system so average (as far as we know), so it's highly likely that life exists or has existed elsewhere.
The alternative is the anthropocentric view that the entire universe was created merely for our viewing pleasure on Earth.
Agreed with cmrdporcupine. The anthropocentric view is actually the idea that because life exists for us, it therefore isn't that special and is likely to have arisen somewhere else - we are anthropocentrically biased to think that life is more likely than it actually is because we ourselves experience it.
Or that the universe is so diverse and complex that assuming that this same rather random event occurs in the exact same way multiple times in many places is also quite arrogant.
No one is claiming that a random event (?) occurs the exact same way. They just use statistics, based on some known factors and yes, a lot of guesses.
We know how stars form, how galaxies form, how solar systems form. We know the general consistency of the galaxies around us, and some systems in our same galaxy. It's not a big leap to assume that some percentage of them will be hospitable (for a time) for life, at least life as we know it.
I'd say the arrogant views are that the whole universe was created for us, or that life must be thoroughly plentiful throughout the universe. The least arrogant view is that it's somewhere in-between, but more importantly, to always adapt to the latest evidence.
Pulling probabilities out of your behind is not statistics. Currently we have an anecdote and you want to extrapolate from that. That's shoddy science.
Even further, we know very little about abiogenesis. And even if we did that would only explain the development of single cell prokaryotes. Eukaryotic cells are of immense complexity, we haven't found anything "between" prokaryotes and eukaryotes, and I haven't heard many good working theories for the explosion of them, and then beyond that multicellular organisms.
So to try to extrapolate that to the "inevitability" of complex life in the universe is like saying that your name will be spelled out in ASCII in the repeating digits of Pi somewhere. Maybe? Can you prove it? No?
I'm not a philosopher of science, or statistician. But the assumption that somewhere there are things "like us" seems to be both arrogant and very teleological -- an implication that the universe proceeds towards an order very similar to us. (Popular science fiction is infested with this kind of telelogical narrative.)
And contrary to arrogantly thinking earth-life is special and unique my argument is that we are just one of a rather infinite variety of "things" in the universe. Life is amazing and complex -- but so are the clouds of Jupiter.
> But the assumption that somewhere there are things "like us" seems to be both arrogant and very teleological
Well, "like us", inasmuch as an entity that is self-regulating, and capable of response to external stimuli. The most basic assumptions for life.
So yes, at some level it is arrogant to assume there's anything else like us. Your view is very nihilistic. But, until we know of other sentient species, it is all about us. We are, as far as we know, very lonely, ex-nihilio orphans in the vast universe. It's only arrogance to nothingness to posit there might be more life in the universe. It is not arrogant to humanity.
So, yes, we are in many ways better than clouds of Jupiter. But of course it is us making that claim. So what? Allow humanity some slack. If we have offended some unknown creator with our supposed insolence, perhaps it should make itself more easily known.
Yes, because if we make it out there, I don't want to deal with having to get rid of the life there just so we can use the space. I am sure humanity will advance to use at least 50% of the space before our sun goes nova, if Moore's law is any indicator of technological advancement.
Liu Cixin's The Dark Forest has an interesting take on this. Basically it's conceivable that the game-theoretically optimal policy is to kill any other sentient species you come across, even if it means you lose access to whatever resources they currently have. This argument falls apart at some point, because it's (presumably) not optimal for all humans to try to kill each other all the time, but it's an interesting idea nonetheless.
actually, the odd thing is how seemingly quickly abiogenesis seems to have occured on earth; few 100 million years give or take. This may mean that given proper planetary conditions, life just tends to happen rather easily - ie for a quite sizablle fraction of candidates at least. Or maybe that it's not going to happen at all unless it happens improbably quickly.
Basically we can't say a much about what the fraction of planets that develop life to planets that have conditions for developing life is based on just one example, but there's no apriori reason for particular pessimism about that number just yet.
Now how likely the conditions are to begin with is a different matter. They've certainly improved in the last decade, since planets at least seem to readily form and earth-sized things too, and apparently easily end up in orbits that could allow for water to exist etc. There's clearly a bunch of other potential conditions that may be necessary for abiogenesis -- untill we know more about how exactly it happens, we can't tell (and actually finding separate origins of life would greatly help in undestanding what that is)
I for one think it very likely this particular planet isn't habitable, because Proxima is such a lousy star, but it's certainly not ruled out. But also that microbes are likely reasonably common in the universe. Around a small fraction of the total number of stars, only some small percentage of what we'd consider candidates today based on their sizes and orbits -- but still that leaves immense numbers.
If further climate outcomes continue to track Hansen's thus-far correct 35-year-old predictions [1], then we've already passed some kind of tipping point and "the heat death of everything" could potentially mean Venusian-style anthropogenic cooking of Earth in some worst-case scenarios, and mass population dislocations and mega-scale environmental disruptions in milder scenarios.
If it turns out that life as we know it is exceedingly rare (and I must admit that the more we find out about exoplanets, the more disconcerted I am while realizing that the hazy possible solution space to the Fermi Paradox is becoming rather uncomfortable as the resolution grows with each passing decade), then that would be truly a tragic outcome.
I believe GP was referring to the heat death of the universe [0], which might be paraphrased as the death of heat in the universe, rather than lifeforms on one planet dying when the environment becomes too hot for said lifeforms to survive.
I should have been clearer; I trying to note the irony of saying "heat death of everything" could be a much shorter timeframe than we usually mean when we say that phrase, if Hansen's forecasts turn out correct.
Why you don't want to share the universe? I think it will be so nice to have a company in this vast universe!
Somehow we always feel that aliens would be always bad to humans, there might be good aliens also somewhere who might help us in solving our current diseases/share advance knowledge or even give us new resources!
>>It would be so much nicer just to have it to ourselves. Let us do what we want, wherever we want, without interference until the heat death of everything.
For all practical purposes we have it all for ourselves and we are doing nothing with it.
There is no serious investment in seeking a different home outside of earth.
Give us time, sheesh. We only figured out how to write a few thousand years ago. If we've been here for a billion years and we still haven't gone anywhere, then you may complain.
We can't calculate those odds. We can't even start. It's like trying to calculate the likelihood that future AI will destroy humanity. We just can't know because it's so deeply theoretical.
For that reason, it seems absolutely absurd to me that someone would say with certainty that life exists elsewhere in the universe. We just can't know. The unlikelihood of its existence could be infinitely high and we might just be lottery winners. Who knows?
And frankly, I hope we're alone. I really don't want to share the universe. It would be so much nicer just to have it to ourselves. Let us do what we want, wherever we want, without interference until the heat death of everything.