

What Earth Tells Us About Life, Intelligence and the Universe - dnetesn
http://nautil.us/blog/what-earth-tells-us-about-life-intelligence--the-universe

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placebo
> Earth is about 4.5 billion years old, and early forms of life were
> definitely on the planet by 3.7 billion years ago. That bare fact seems to
> imply that it wasn’t hard to get life going on Earth; if initiating life was
> really improbable, then we should have had to wait a long time before its
> appearance.

I think that's a big leap to make in drawing conclusions exactly because of
the N=1 problem. If we had managed to reproduce a process by which a bunch of
organic compounds turn into a the simplest cell type then we could start
talking about probabilities of this process happening elsewhere in the
universe. It might very well be true that life would start just as easily
elsewhere but that conclusion can't be based on the amount of time it took
life to appear on earth. The fact that someone wins the lottery the first time
they buy a ticket does not mean its easy to win the lottery...

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throwaway_yy2Di
_" Earth is about 4.5 billion years old, and early forms of life were
definitely on the planet by 3.7 billion years ago. That bare fact seems to
imply that it wasn’t hard to get life going on Earth; if initiating life was
really improbable, then we should have had to wait a long time before its
appearance."_

I think it's a significant observation that there's just a single origin of
life -- that after a 4.5 Gy sample time, we only observe one type of
biochemistry. If you predict abiogenesis happens easily, you should expect it
to have happened again independently, many times, and expect to find distinct
classes of radically different, "alien" life on earth.

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cLeEOGPw
Not necessarily. It might have happened that different types of chemistry
appeared, but as life evolved, one type pushed out the other. So we can't
really tell if life happens easily or not from the fact that there's one type
of biochemistry here.

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ZanyProgrammer
Isn't the discussion about extraterrestrial life pretty much entirely
speculation?

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charlieflowers
I guess in the same way the Higgs Boson was speculation, or string theory is
speculation. It is a valuable hypothesis that is not proven yet.

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mod
IANAP, but I think the hypothesis is more that it's incredibly likely that
life exists.

We have no evidence that it does, only that Earth-like conditions are not
unique.

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millstone
A serious question: why are earth-like conditions suggestive of
extraterrestrial life and not, say, extraterrestrial McDonalds? The observed
frequency is identical so far.

I think the answer must be a bias towards believing in some essential
specialness or uniqueness of life, which isn't supported scientifically.

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givan
It tells us very little, there are more stars in the universe than sand grains
on earth
[http://www.npr.org/blogs/krulwich/2012/09/17/161096233/which...](http://www.npr.org/blogs/krulwich/2012/09/17/161096233/which-
is-greater-the-number-of-sand-grains-on-earth-or-stars-in-the-sky) and we
don't even have the technology to properly search our solar system, our sand
grain.

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cLeEOGPw
Considering prospects of living, stars in other galaxies are irrelevant,
because they are unreachable. We should, at least now, look at the closest
stars around us, which are very few. There's reason to believe even these
might be unreachable for us.
[https://en.wikipedia.org/wiki/Great_Filter](https://en.wikipedia.org/wiki/Great_Filter)

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vorg
There could be other filters not listed. I sometimes wonder why on the Earth
the observed sizes of the Sun and the Moon are the same, and recently wondered
if the effect is far better eyesight in some land animals, including humans,
than would otherwise be the case. If the Moon looked larger than the Sun, the
Sun would disappear more frequently and for a longer time in the daytime, and
there'd be no corona; if vice versa, the eclipse would only ever be partial.
Because the corona lasts 5 minutes only, once a lifetime, animals will stare
at it in surprise. Only animals with eyes which won't be damaged by sustained
bursts of daylight will pass on their genes. Perhaps it also gives rise to
animals which can see both in the dark and in the bright light. Is such type
of eyesight essential for higher intelligence? If so, it's part of the Great
Filter, reducing the odds of intelligent life by orders of magnitude.

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lordnacho
But all the intermediate steps suffer from the same n=1 problem. In fact,
those difficult hoops themselves cannot be identified when there's just one
experiment.

How are we to know that our experiment is not just an outlier in some way?

I guess there will be more data when we have a closer look at some of these
exoplanets.

