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Comment by caymanjim | Hacker News Reader

> So if they were inhabited, what happened to them? Are they exactly at our level of development? Earlier? Hopefully. Because later poses some real big questions - does technology top out about where we are now - no FTL travel, no really big radio transmitters or stellar engineering? No probes to nearby star systems? Did they even make it past the nuclear age, or avoid wrecking their climate?

You get more than one chance. While finding intelligent life would be great, finding any life is nearly as great. We might not catch them at a comparable technological moment, but over 8 billion years, intelligent life could have come and gone many times. All we need are some biosignatures to confirm that something's out there, and exploration will kick into overdrive.

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I think there’s no technological barrier there, but cultural choice: if there’s no good economic reason to go to space (ie That has a high enough rate of return within a short enough period of time), we may just die out before doing any of that stuff. I think about that every time someone argues human spaceflight is worthless. I don’t think they’re wrong in the short-term, but the societal consequences are the same as if the entire species just decides to stop having children entirely because there’s no good economic reason to do so.

Especially thinking about this near the anniversary of Apollo. What if that was the greatest extent of human travel in space? To me, that’s so sad.

https://m.xkcd.com/893/ “The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space--each discovered, studied, and remembered by the ones who made the irrational decision.”

Actually if we find life on other planets that is bad news for us as a species:

https://www.technologyreview.com/s/409936/where-are-they/

> While finding intelligent life would be great, finding any life is nearly as great.

That would actually be worrisome. If we found and detected microorganisms on nearby planet e.g 12 light years away from earth, then that means we are probably headed for extinction.

The reason is the theory of the Great Filter. Given that we have not been able to observe any kind of activity outside of our solar system, it means that either life is rarer than we think or that entire civilisations go extinct pretty quickly.

If we find microorganism on a nearby planet, the logical conclusion is that life is not as rare as we think but evolved civilisation such as ours simply go extinct in a relatively short amount of time.

The Great Filter may be ahead of us.

I think you have a slight misunderstanding about the great filter.

If we found only microorganisms on the other plant that should indicate that the filter is behind us, life having died out on that planet before even reaching large scale organisms let alone technology.

If we find ruins of civilization and technology on the planet at either about the same stage as us or more advanced, then we can assume that the filter is ahead of us.

Not so. All we know from finding micro organisms (or any other form) is that the filter is after that stage. It may well be between micro organisms and us but that seems unlikely.

Have we done anything that we'd be able to detect from 12 ly?

The window for detection at different power levels is probably quite small.

Very early radio would be somewhat weak. The middle phase of analog transmission probably has some higher power levels. The digital phase would coincide with rapid decreases in detectability.

That assumes every planet capable of supporting life a) has life and b) develops intelligent life. If only 1% of planets capable of supporting life develops life and only 1% of those develop intelligent life then it is extremely unlikely these two nearby planets would have any life at all. Even if you bump the odds to 10% or even 33% the odds are still against it.

For sake of argument assume we (or they?) won the lottery and intelligent life exists. Make an even larger stretch and assume that life is technologically capable, has been for 10,000 years, and didn't destroy themselves (achieving a stable population size and reasonable resource usage). Even then the odds are against us detecting any kind of radio transmissions.

Our radio transmission bubble is far beyond 12ly. The question is how sensitive an instrument we'd need to detect it. IIRC, there are some pretty big bursts in ther along with the general noise.

There'd also be significant signatures in the composition of our atmosphere.

ok, assuming you mean that nuclear war is the threat to all civilizations (because once we advance to the point of developing nukes, eventually some asshole deploys them irrationally).. why isn't this a solved problem? I.e: create underground societies that are nuclear-powered and sustainable for centuries, and impervious to nuclear attack?

Not necessarily. Live != civilization, so just because many planets may have developed live (or obtained it via panspermia) but only very few (or one) have developed multi-cellular live (which even on earth is quite recent) and even less a civilization comparable to us humans.

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