Dear Yousuf Khan:

On Saturday, August 18, 2012 6:23:33 PM UTC-7, Yousuf Khan wrote:
On 18/08/2012 6:42 PM, dlzc wrote:
On Friday, August 17, 2012 4:23:08 PM UTC-7, Yousuf Khan wrote:
On 14/08/2012 6:12 PM, dlzc wrote:
On Tuesday, August 14, 2012 1:47:20 PM UTC-7, Yousuf Khan wrote:
On 11/08/2012 12:06 PM, dlzc wrote:
....
Well, now we're getting into science fiction.

What is writing an equation to predict
the probability of civilizations on other
planets, based on assumptions of
flatlanders like us?

That's just stastical extrapolation, based
on factors we are currently aware. As we
become aware of more factors, then those
factors get incorporated into the stats
later too. At some point there will be
enough factors accounted for that the
equation will be right.

So, you agree it is just science fiction, the way the masters do science fiction.

So what intelligence were terraforming
us? And who terraformed them?

I doubt they were interested in ending
up with us, just with our biosphere.

So where are they now?

Civilization dead and gone, on a exoplanet near us perhaps. But could easily be anywhere in the Milky Way.

If they spent all of that time and effort
terraforming us,

Its just launching a probe, a chemical release weapon.

then why didn't they stick around or leave any
archaelogical indications of their existence?

They probably did, on their planet. If some race were propagating this way, they did not have any better idea to get between stars than we do. For that matter a supernova might have simply done the "spraying" for them.

Viruses must've been changing lots of DNA
code prior to that, but Snowball Earth happened
only once (so far as we know).

We have tidal rhythmites dating back to 2.2 Gy,
not that that helps, but there were a few
periods of glaciation indicated there, when lunar
recession was nearly stagnant (no tides =
"Snowball Earth").

How do these indicate periods of glaciation?

Free surface water does not exist if we
are a snowball. No free surface water means
the tides are not large enough to accelerate
the Moon to a higher orbit.

Okay, but what are rhythmites?

I would have thought you'd at least look...
http://www.mantleplumes.org/WebDocum...derESR2004.pdf
http://www.colby.edu/geology/RAG_356...rEtAl_1995.pdf
http://geology.gsapubs.org/content/32/10/841.abstract

It is a fossil record of tidally-influenced sediment. A big enough piece gives us length of month, length of year, and the sediment itself gives us *when* it was produced. Get enough pieces from enough places, and you get a pretty thorough record.

....
That's assuming that panspermia is just allowed
to drift in randomly. If we were terraformed,
then it was probably aimed at us pretty precisely,
rifle-style, rather than shotgun-style. If rifled
at us, I doubt a puny little solar wind is going
to stop the stuff from coming in.

Would have to be to get past a stellar
sheath once the inner system was swept
clear, and planets had formed.

You can always bring it in on spaceships,
no worries about stellar winds then.

Not if you died because you traveled at 0.1c or higher (the protons look like radiation then), or if your "century ships" systems failed. Only an FTL drive could get "corporeal" terraformers here to leave traces.

David A. Smith