[ExI] kepler study says 8.8e9 earthlike planets

[Kelly Anderson]

On Thu, Nov 7, 2013 at 7:55 PM, spike <spike66 at att.net> wrote:

>
>
> *From:* extropy-chat-bounces at lists.extropy.org [mailto:
> extropy-chat-bounces at lists.extropy.org] *On Behalf Of *Kelly Anderson
>
> The "earth like" definition used by the scientists that wrote the paper
> include approximately three variables. Rare Earth proposes around 12 such
> variables if I remember correctly…
>
>
>
> Ja, but the three variable case makes more sense for reasons I will give.
>
>
>
> >…For example, we need a molten core and plate tectonics in order to get
> the right metals to the surface…
>
>
>
> A molten core follows directly in most rocky core planets.  They have an
> enormous amount of heat from potential energy conversion as the rocky dust
> congeals.
>

And yet mars currently lacks a molten core. It also lacks the magnetosphere
that would protect martians from radiation. Would mars count as one of the
planets counted by NASA in this survey?


> >…provide both land and ocean (for the evolution of land animals, since
> hands evolving on a fish seems like a bit of a long shot) and other reasons
> …
>
>
>
> Perhaps.  But I haven’t been able to convince myself that intelligence
> could never evolve in the sea.
>

I think there are reasons that it is unlikely. One piece of evidence is
that the most intelligent sea animals are land animals that have returned
to the sea.


>
> >…Then there is Jupiter and Saturn filtering out the comets. Very useful
> that…
>
>
>
> Useful but not necessarily critical.  If you had a Goldie with oceans 50km
> deep, a good sized comet or other hunk of space debris could strike the
> planet without wiping out all the biota.  An ocean planet could still
> reasonably have ice caps, or for that matter be ice everywhere, with liquid
> oceans below.  Then it is conceivable that life could be air breathing on a
> planet with no rocky surface anywhere.
>

Sure.


>
> >…If you refigure all of the Rare Earth variables in with NASA's numbers,
> I'm guessing you would end up with a MUCH smaller number. –Kelly
>
>
>
> Ja.  I found Ward’s Rare Earth a bit too narrow minded on what kind of
> life forms could become tech enabled.  He might be right.  But it just felt
> like he was over reaching just a bit.
>
>
>
Probably. Rare earth is loved by creationists, which also makes it a little
suspect. I haven't read the book myself, so I dare not comment further on
the book itself.

-Kelly
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