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A Lonely Universe

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Re: A Lonely Universe

#21

Post by pklausler »

Causality1 wrote: post #2

Either intelligent life is rare in the universe or there's something that happens to it that prevents it from what we envision as the future of our own species, i.e., colonizing and spreading among planets. Maybe 99.99% of species ruin their own climate before getting off-world. Maybe they all decide it's happier living as hunter-gatherers. Unless we're alone, there is some fate that's common to all intelligences and…

I agree; any galaxy that produces even one civilization capable of launching self-reproducing interstellar probes will never be the same afterwards; it's like a phase change. We don't observe any activity from Bracewell - von Neumann probes today -- nothing is rampaging through our asteroid belt turning it into new probes.

The thing to remember is that given enough time and space, nearly every event has probability 0 or 1. BvN probes are either impossible or inevitable.

Re: A Lonely Universe

#22

Post by lkrubner »

We know this much from planet Earth, and therefore this should be our starting point when considering life elsewhere:

The Earth is 4.5 billion years old.

Life existed by roughly 3.5 billion years ago, possibly earlier.

Multicellar life only got going about 0.7 billion years ago.

So, roughly speaking, 1 billion years to get to life, but 4 billion years to get to multicellular life. So we know that multicellular life is 4 times more difficult than life itself.

So for every 4 planets where we find life, we should expect 3 of those planets to only have single-celled life.

Of course, it is possible that life arose on Earth as early as 4 billion years ago. We have no record of that, partly because the Earth was still getting hit by asteroids that left craters 1,000 kilometers in diameter (we know this because we can see that the moon was hit with these asteroids, back at that time). Since such events would sterilize the planet, that would also imply that life re-started many, many times. But it would also mean that the single-cell/multicell ratio is more like 1 in 8.

Re: A Lonely Universe

#24

Post by lubujackson »

Causality1 wrote: post #2

Either intelligent life is rare in the universe or there's something that happens to it that prevents it from what we envision as the future of our own species, i.e., colonizing and spreading among planets. Maybe 99.99% of species ruin their own climate before getting off-world. Maybe they all decide it's happier living as hunter-gatherers. Unless we're alone, there is some fate that's common to all intelligences and…

The third option is that everything is simply too far apart and any detectible transmissions are either too faint or buried behind all those massive fusion furnaces.

For instance, if our best Earth tech was pointed at Earth from a distant star, how far away would we be able to detect our own traces of life? We know that life is "a little rare" at least, but there is a huge range of rarity where life is everywhere across the vast, vast universe but sparse across the dinky number of light years we could see each other. Maybe aliens have tech that is 10,000x better than ours but the scale of distance is just too big of an obstacle.

There is an assumption that alien races must have figured out things well beyond our understanding and be doing things like harnessing stars in some dramatic way, but maybe that just isn't a reasonable thing for life forms to do? Or if they do have that ability, they may operate on a much longer timeline, simply nudging things along in a way that escapes notice.

Re: A Lonely Universe

#25

Post by UncleOxidant »

api wrote: post #12
elorant wrote: post #5

Earlier quoted context omitted.

Actually, the universe might be too young for life, and we're one of the first. The further you go back in time the more violent events like supernovas you'd find which would make the universe a very hostile environment for life.

I think this is likely. Always remember that intergalactic travel is exponentially harder than interstellar travel and that is already brutally hard. We need only be among the first in our galaxy to explain the Fermi paradox.

I don't see how there could ever be intergalactic travel.

Re: A Lonely Universe

#26

Post by [deleted] »

lkrubner wrote: post #22

We know this much from planet Earth, and therefore this should be our starting point when considering life elsewhere: The Earth is 4.5 billion years old. Life existed by roughly 3.5 billion years ago, possibly earlier. Multicellar life only got going about 0.7 billion years ago. So, roughly speaking, 1 billion years to get to life, but 4 billion years to get to multicellular life. So we know that multicellular life i…

[deleted]

Re: A Lonely Universe

#27

Post by UncleOxidant »

furyofantares wrote: post #14
bitcharmer wrote: post #8

Earlier quoted context omitted.

> Personally I think just the fact the universe hasn't been eaten by Von Neumann machines means we're alone. Or maybe it'd make sense to consider how big the Universe is, how fast it expands and combine it with how very local is our perception of it. If you do that and account for how young our capabilities to hear and see stuff out there actually are, Fermi's paradox doesn't make any sense just like the certainty of…

The fermi paradox makes sense within "just" the milky way, so the size of the entire observable universe or the speed it expands doesn't seem relevant.

But what if he was overestimating the the frequency of intelligent life emerging? Yes, it's quite possible that there are many simple lifeforms spread throughout the galaxy, but what if we're the only intelligent life that's emerged in the galaxy? Sure there could be intelligent life elsewhere in the universe but we'd never find know about it because the distance between galaxies is so large.

Re: A Lonely Universe

#28

Post by [deleted] »

frazbin wrote: post #16

Fun! But if abiogenesis happened more than once, and we don't see any alternate-root lineages, then we've admitted the possibility that major advances towards complex life can have a resource lock out effect leading to the extinction of alternates; this could apply to any or all of the critical steps towards technological intelligence. e.g. did the evolution of homo sapiens and its subsequent monopolization of earth…

[deleted]

Re: A Lonely Universe

#29

Post by TrispusAttucks »

Causality1 wrote: post #2

Either intelligent life is rare in the universe or there's something that happens to it that prevents it from what we envision as the future of our own species, i.e., colonizing and spreading among planets. Maybe 99.99% of species ruin their own climate before getting off-world. Maybe they all decide it's happier living as hunter-gatherers. Unless we're alone, there is some fate that's common to all intelligences and…

> Maybe they all decide it's happier living as hunter-gatherers.

Wouldn't this be great! Screw universal dominance. Let's play in the woods and hangout with nature. Heat death is coming no matter what.

Re: A Lonely Universe

#30

Post by kingcharles »

Causality1 wrote: post #2

Either intelligent life is rare in the universe or there's something that happens to it that prevents it from what we envision as the future of our own species, i.e., colonizing and spreading among planets. Maybe 99.99% of species ruin their own climate before getting off-world. Maybe they all decide it's happier living as hunter-gatherers. Unless we're alone, there is some fate that's common to all intelligences and…

How about the possibility that perfect VR is invented, every person can live inside their own perfect universe, and the whole species just doesn't give a fuck about exploring the (real) universe?

That would stop a civilisation from exporting any spacecraft or signals outside its homeworld.

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