5 ms·
True. But we have prima facie evidence that advanced civilizations -- as advanced as we're about to be, in not very much longer -- are very rare.
by mnemonicsloth 7y ago
True. But we have prima facie evidence that advanced civilizations -- as advanced as we're about to be, in not very much longer -- are very rare.
- deleted 7y ago[deleted]
- nickthemagicman 7y agoFinding life on other planets means life was probably seeded on earth instead of the 'Spontanous Generation' theory of biology where RNA just happened on earth at some point. It also opens up the possibilities of life existing outside of earth. I don't know whats not mind blowing about that.
- mnemonicsloth 7y agoAs a biologist, it's pretty cool, although not quite as cool because it's the same life. Different life, evolved on different planets, would be cooler. It would use some of the same tools, like phosphates as signaling/energy molecules, because nothing else can do the job. But alien life could use different amino acids from the ones we use, or something different from amino acids instead. They would probably be linear polymers of related monomers though. The same goes for DNA: different base units probably, but still a linear polymer, and very possibly a helix (lots of things are helices). But the problem with all these instances of life is that all but n of them have to get snuffed out before they've developed much further than we are, and so far as we know n has to be either 1 or 0.
- aaronblohowiak 7y agoDon’t pressures and temperatures impact which chemical classes can do which job?
- mnemonicsloth 7y agoIt depends on how far out you want to get. It's possible life could exist on neutron stars, or in stellar photospheres, or in the atmospheres of gas giants. And life might not be obvious. Life as we know it is not an obvious prediction given carbon, hydrogen, oxygen and nitrogen as a starting point. So maybe it turns out that certain combinations of minerals do something interesting when you immerse them in an ocean of liquid chlorine. We wouldn't know. But so far as we know for sure, life has to start with liquid water, which narrows the range of admissible temperatures to 0-100 C and pressures around 1 atmosphere. Hyperthermophile bacteria can live in boiling water (up to 120C). We use some of their enzymes to do genetic engineering on normal cells. The temperature change isn't enough stop the hyperthermophile proteins from functioning (and they're pretty sensitive). Likewise there are psychrotolerant (cold-dwelling) cells that can live near 0C, using mostly normal proteins. So I think life as we know it is locked into one regime of "normal" chemical behavior.
- nickthemagicman 7y agoAlso as a biologist,finding life on other planets..no matter what the form...would be mind blowing as fuck to me. Sorry you're so jaded.
- sokoloff 7y agoDo we have evidence of that? It seems like we've not looked in sufficient detail at a sufficient number of solar systems to reach a conclusion of "very rare".
- lioeters 7y agoI agree, absence of evidence is not evidence of absence.