[ExI] kepler study says 8.8e9 earthlike planets

[spike]

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.

 

>.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.

 

>.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.

 

>.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.

 

spike

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