It’s a long sequence of random chemical reactions to result in the build-up of something advanced enough to fall under the heading of evolutionary advancement. But we don’t know what that sequence is nor how likely it is to occur. Assuming that because there are a trillion planets out there that the odds of that particular sequence of events MUST be GREATER in occurrence than 1 in 1 trillion is not science, it’s just hope. At the moment, we have no evidence that the odds of life forming, spontaneously, isn’t exactly 1 in the total number of planets in the universe, given that we only know of one planet that has formed life and we have no particular reason to think that the chemical sequence to have gotten to amoeba was anything less than stupendously complicated and improbable.
Now, given zero information at all, we would want to assume that we were an “average” planet. If you only have on sample to look at, “average” is the safest bet - but still a really bad bet.
We have better information than that, though. We can look out there and see if anyone is flashing us. If we were near average, we would expect about half of all stars to be sending out some signal. We would probably expect aliens to be stopping by to say hello every few decades. We’re definitely not near average.
At the moment, I’d say, the real question is not “how many planets are there in the universe?” The question is, “If I take some raw, unjoined atoms, stick them in a pot 10 foot square and 1000 feet tall, and put a heat lamp at one end, how long will I have to keep the system cooking before something knocks on the lid, asking to be let out?” Once you can math that, then we can start asking how likely life is.
I think sentient life in the universe is analogous to camera flashes at a large concert arena.
Each flash represents the rise and fall of a sentient species. So getting two of these flashes to flash at the same time, and then developing the technology to communicate with each other, in the relatively short time both flashes are still on is exceeding rare.
I believe microbial life is everywhere. I’d bet the farm you’d find it on more than one moon right here in our own solar system.
The belief in life elsewhere is the same as belief in God or belief in space turtles. A pleasant idea with very little evidence other than a useful explanation for how absolutely crazy it is that we’re here.
I come down firmly on the agnostic side of things. I have no reason to believe or disbelieve in planets full of space algae or what have you. Proof either for or against the idea would not surprise me. Good luck in your beliefs.
They talked to the experts and those said: you have to take time into account. There are many, many planets that could potentially harbour life, yes. But our kind of life is, on a cosmic scale, so recent, and so shortlived. It is highly unlikely that two or more such short sparks would exist in the same time.
I’m an agnostic about extraterrestrial life, and see no reason to assume thta the universe is teeming with life.
My two main objections :
-We’ve absolutely no clue about how likely it is that life can appear even if conditions for life to appear are nearly perfect. It could be one chance out of a trillion of trillion of trillion, for all I know.
-We’ve no clue what are the conditions required for life to appear. It could require extraordinarily rare circumstances. For instance, some people believe that our abnormally large satellite was necessary because it stabilized the condition on Earth. It could also be that not having even a single life extinction event on a planet is absurdly unlikely, to give another example.
Also, intelligent life is another kettle of fish. It appeared extremely late on Earth, and given how long life was thriving without a single intelligent specie appearing (as far as we know), it could have been this way until the sun expanded and fried everything. I’m also extremely pessimistic about the chance an advanced civilization has of lasting long. To be clear, I strongly suspect we’re going to off ourselves soon one way or another. We’re too intelligent and powerful for our own well-being.
On the other hand, I don’t think that interstellar travel would be a massive issue if there was actually a long lasting intelligent species. At some point during the next 50 millions years, we’d find a way if we were to last that long.
One of the most chilling hypothesis wrt to the Fermi paradox is that there are a lot of extraterrestrial civilizations. But they stay hidden. For a good reason.
Maybe we’re better off not making contact with anybody.
The fact that there is only one genetic code (with a few variations) is pretty strong evidence that all current life on Earth descends from a single origin.
It’s possible that life may have originated more than once, but there is no definite evidence it did so. If so, descendants of the other origins have disappeared.
There have been scenarios propoes in which life developed first on the surface, or first at hot sea vents, but even that is debatable.
It’s a common belief among humans, as this and many other threads attest.
But does the fact that this belief is so common say something about the universe, or merely something about humans? Given the actual evidence we’ve thus far been able to turn up, I’d say the latter.
There’s the old story about the Emperor’s beard: No one is ever allowed to set eyes on the Emperor of China, but the question arises: how long is the Emperor’s beard? An enterprising scribe undertakes to determine this by asking as many people as possible to give their answer, then averaging all the responses. The result is a length of amazing precision - that has no relationship to reality.
While I may not go as far as “every couple of solar systems”, I’m still leaning more to the “Yes, life is probably fairly common” side, just given how soon it arose in the prehistory of Earth. Basically, in geological terms, an eyeblink after the last major impact events stopped.
This is mistaken - I can’t think of any current credible proposal for life originating on the surface, it’s been proposed as either happening in shallow seas or vents, with some outside non-aquatic theories like Gold’s “deep-hot biosphere” and panspermia. But never just on the surface. Water being pretty essential for the current models of abiogenesis.
There is a crucial difference. There is zero evidence for gods or space turtles and no plausible mechanism put forward for their potential existence. I think it is a category error to place them in the same argument.
On the other hand, we* know for a certainty* that simple life arose at least once. Though we haven’t nailed down the “how” there are various plausible mechanisms hypothesised.
Cosmological investigations seem to confirm that our galaxy, star and planetary system…whilst all fascinating and unique, aren’t particularly remarkable. Given a hundred billion galaxies, each of 250 billion stars and perhaps 10 billion years to play with, it doesn’t seem particularly outrageous to consider that other life is out there (or out then!)
in the graped section, I think you might have overlooked the factor that a planet, and duration of time, provides many quadrillions of opportunities for random chemical reactions to try, retry and try again. Planets are huge, atoms are tiny - each planet isn’t just spinning the wheel once, then stopping.
I’ll have to do some research but I know I just recently watched a documentary (life from minerals? Or something like that.) where they hashed out life occurring on the surface and at the sea vents.
I suppose it’s possible I’m remembering some of the details wrong.
