Scientists find promising hints of life on distant planet K2-18b

www.bbc.com

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I would be so happy if we did find life in the universe.
- Non-existence of life outside Earth is more outlandish than there being life out there, isn't it? It should be the default assumption.
  
  That's been the theory, but supposedly more and more scientists have been coming to the belief that if it was out there, we should have observed it in some form by now.
  
  We've barely been able to detect the most easy-to-detect exoplanets for just a few decades. I don't think anyone can say one way or the other yet.
  
  I agree
  
  It really just.. isn't. All our knowledge of statistics and probability are practically useless when faced with one, singular distinct data point and no understanding of how life started.
  We're not talking about farcically artificial stakes; if the probability of life appearing on any given square meter of any planet, every second, was, say, the odds of shuffling a specific set of cards. Then, even given 20 sextillion (2*10²²) planets, an optimistic 10³³ seconds until all stars and planets are gone, and 10¹⁴ square meters per planet, the likelihood of life appearing once, anywhere in the universe before heat death is still practically zero.
  But that's all a guess. So long as we don't know the likelihood of life starting, we simply cannot have a 'default assumption', it makes no sense. There is an altogether plausible reality where we are the be all and end all of life in the universe.
  
  We already know life happened once. I feel like that updates any prior enough above 0 that, given the literally (?) infinite number of planets, the probability of life occurring somewhere else is 1
  
  There are not an infinite number of planets, (in the observable universe, there are roughly 20 sextillion, which is why I chose that number) so I'm afraid not.
  
  I see sources with planets in the septillions? Larger than sextillion. And many more outside the observable universe. I think it is safe to call that infinite
  
  The point is, even if there were septillions OF septillions, the chances in my example are STILL basically zero. My example wasn't about specific numbers, but to exemplify how something seemingly likely (like 'life exists elsewhere') might actually be mind-bogglingly near-impossible. Just because I shuffled a specific card order once, doesn't mean it will (or realistically can) happen in all the universe for all of time ever again.
  Nobody can know what's outside the observable universe (and for all intents and purposes, nothing outside the observable universe really "exists").
  As far as we can (possibly ever) know, there are not infinite planets. Though it's a philosophically attractive idea, there is no evidence to suggest it's true.
  
  Exactly. Consider one observation about Earth life. We know that life started pretty early in Earth's history. It happened within a few hundred million years of Earth no longer being a ball of molten slag. But I can explain that observation with completely opposite conclusions:
  Life may be easy to start. It happened so soon, that life must form nearly anywhere once conditions are sufficient for it. Simple bacterial life is an inevitable process. It's likely our own solar system is brimming with life, with every deep Martian aquifer and outer system ice shell moon overflowing with simple life forms at a minimum.
  Life may be incredibly difficult to start. You'll have to scour a billion galaxies before you find a planet with life as complex as Earth has. But we can only exist on one of those lucky oddballs. The only chance complex intelligent life has of forming on a planet is if everything goes absolutely perfect. If the evolution of life were delayed by a billion years, we wouldn't exist. Within a billion years the warming Sun will boil away Earth's oceans. Our evolutionary time frame is freakishly fast compared to the average. The fact that life started so early is simply a selection effect. We can only exist on a world that evolved complex intelligent life, and that required breakneck pace evolution.
  Even this one observation, that life started early, can be explained with completely opposite conclusions. The simple truth is, as you note, we can't know anything about life's prevalence with a sample of only one. That's why we really should work hard to search the solar system for present or past life. It's one of the few shots we have short of interstellar travel of actually determining the prevalence of life.
  I'm also skeptical that we'll ever be able to prove life via chemical detections like this one. The problem is that while we may not know of a way for a compound to be produced without life, we can't ever be certain that there isn't some unknown non-biological route for that compound's synthesis. It's an unknown unknown. Maybe dimethyl sulfide can form without life, but in some odd conditions that just don't exist on our planet. We can't prove there isn't some non-biological way to form it. There are really only two ways to prove that a planet has life on it:
  Physically go there or bring back samples. Find said life, examine it with your own eyes or under a microscope, and directly observe it reproducing, reacting to its environment, etc.
  Detect radio or other signals or signatures of a clearly technological origin.
  This is why I'm a big proponent of SETI. Even beyond the prospect of making contact, detecting technosignatures is one of the few ways we could have truly unambiguous evidence of alien life. If you find some loud laser or radio beacon belching out long strings of prime numbers, well, you've just proven beyond any doubt that life exists outside of Earth. Maybe that life is long dead. Maybe the life forms were replaced by machines. Who knows. But if you find something clearly technological out there, you can know for certain that there had to be life involved somewhere along the chain from dead random matter to interstellar beacon.
  
  All true, though even "detecting signals" isn't so unambiguous, there was that hoohaa about 'regular radio signals' that turned out to be pulsars. I'm not sure I'd take a radio signal shouting prime number sequences as proof beyond doubt.
  Interesting point about finding past life, though. If we could find any proof that life even did once exist, we could actually start calculating probabilities of life out there.
- It'd be nice. A good chunk of my climate change despair comes from this planet being the only definitive source of life. Even if we don't find intelligent life, if there's some backup out there for it in general then we aren't extinguishing the only spark in the universe. It's a mixed blessing that this planet is too far away for us to fuck it up too, at least without multi-million year generation ships.
  
  at least without multi-million year generation ships.
  I mean this is probably a bit of an overshoot, its 124 light years. Maybe like 10k years at the current tech
  
  I was just roughly computing it off Voyager 1 at 17km/s. That works out to 2.19m years.
  
  Also within the next 100 years its likely we will put up sophisticated telescopes that use the sun as a lens, such an array could generate enough resolution to see the continents and the colors of those continents of planets within 100-200 light years. China has it on their far future plan iirc
  
  I don't think humans are capable of wiping out life on this planet for good. We'll really mess shit up, there will be untold suffering amongst human and non-human sentient populations alike, but anthropogenic climate change is something that will take care of itself in short (on geological timescales) order once it causes our population to collapse. Life on Earth has survived much worse in the past.
  
  humans ourselves are likely to survive and rebuild new civilizations anyhow. the problem to me isn't us going extinct completely it's all the dying that'll be done before the new world is on its feet

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