204143Re: Universal language for communicating with space aliens
- Jul 26, 20142014-07-23 20:30 GMT+02:00 Warren D Smith <warren.wds@...>:
> The "rare earth hypothesis" is discussed here:And how could anyone be convinced of either of them?
> I personally am unconvinced of its truth or falsity.
>Aren't penguins impressive?
> There are too
> many uncertainties which are too large. It seems clear that advocates
> of both this hypothesis and its opposite have, historically, made
> large errors. Many of the claims that have confidently been made were
> just wild guesses which probably were quite wrong. I find it
> possible that Earth's might be the only life in the entire universe,
> or that intelligent life might be pretty common, with a
> million places in our galaxy harboring it; and everything in between.
> It has been estimated, based on extrapolating from planet-hunter data
> to estimate all the planets we did NOT see
> (planet hunting techniques can only detect planets a small fraction of the
> those fractions can be estimated a posteriori) that 22% of stars have
> an Earth-size planet in their "habitable zone." In fact, by
> correcting for detectability biases they attempt to understand the
> whole distribution of planet sizes, etc. That is explained in
> (click "Full Text").
> It would however, be more convincing if we actually had detected a few...
> Catalogs of over 1000 known planets:
> Also, the whole idea that Von Neumann machines are going to do this or
> that faces the objection that nobody has ever built one, and perhaps
> they just can't both exist and work very well. I do not know the
> answer to that either. Life itself is a Von Neumann machine which,
> even 3Gyr ago was far more capable than anything we can build, and in
> 4 Gyr it has not managed to spread beyond Earth as far as we can tell,
> nor has it even managed to do anything impressive in (say) current
> Antarctica -- which compared to the Oort cloud or Mars seems a very
> hospitable place...
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