Re: poly: polymath digest for 19 Jan 98

From: Damien R. Sullivan <>
Date: Tue Jan 20 1998 - 20:47:58 PST

On Jan 20, 4:38pm, d.brin wrote:

> the case in the proterozoic. Still, I have trouble believing it really was
> at the outer edge, since the transformation to low CO2 was non-linear. It
> happened pretty rapidly. The suddenness might have tipped Earth into a
> total ice age if Earth had really been toward the outer edge. Still Carl
> raises a good point
I'm some distance from my geology texts, so I can't check O2/CO2 dates,
although they may be still unsettled. But I know there's
evidence that a bit before the Cambrian the Earth was very nearly in a
total ice age. The Varangian glaciation, with glacial striations on
rocks thought to have been within a few degrees of the equator at the
time. One of my professors, Joe Kirschvink, was very big on this, so I
can't remember if this is an accepted fact or a controversial idea I was
saturated in. (And again, I'm behind the grinding edge of geology.)

All of which is to say I think there was a nearly total ice age, but I
don't know if everyone agrees, or what the relative timing of atmospheric
or orbital shifting was.

(Free oxygen itself is a couple of gigayears old, I think, but high
concentrations are rather more recent.)

> the entire series, because it sets up his entire premise for why the
> Foundation Universe is the way it is. (In that book, two robots deliberate

If Asimov had gone in for the fast replicators idea popular on this
list, he could have said "humans were first" and left it at that. :)
Strange how I've gone from "human only galaxy? Weird!" to "first come,
only served."

I only skimmed through Benford's book, but he seemed to be throwing out
his own explanation of the human only universe.

-xx- GCU Librarian Bound in Pale Leather X-)

For all the gold Ewan Gillies ever found
Could not buy him peace and freedom
>From the memory of the sound
Of the waves on St. Kilda's rocky shore.
Received on Wed Jan 21 04:50:14 1998

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