[PatrickHenry]

Lots of stuff left out. The website where the review is found has a heavy-duty copyright notice. I assume the little I've posted is "fair use" (whatever that means). The whole review is HERE.

[PatrickHenry]

SETI PING. [This ping list is for the evolution side of evolution threads, and sometimes for other science topics. FReepmail me to be added or dropped.]

[Skooz]

Call me when they land.

[Moleman]

Is there Anybody Out There
Just nod if you can hear me, is there anyone home (/PinkFloyd)

[edwin hubble]

Thanks for the post. (and ping)

The Drake Equation variables are constantly being revised:

Rare Earth now seems more likely...
for its unlikely causal chain:

very early microbial life-->
put oxygen in the atmosphere-->
ozone in upper atmosphere-->
ozone protects water vapor in atmosphere from destruction by UV over eons (this one is essential as all our planet's water would be gone by now - like Venus) -->
water retained in oceans -->
water facilitated tectonic plate movements -->
tectonic plate motion recycled and deposited minerals and metals -->
made technological (metal-using) civilization possible..

Many other unlikely chains of causation; among them:
* Almost circular orbit
* Presence of moon (collision with Mars-sized object) stabilizes the Earth's axis tilt.


Drake Equation:

N = R* • fp • ne • fl • fi • fc • L
Where,

N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable.

R* =The rate of formation of stars suitable for the development of intelligent life.

fp = The fraction of those stars with planetary systems.

ne = The number of planets, per solar system, with an environment suitable for life.

fl = The fraction of suitable planets on which life actually appears.

fi = The fraction of life bearing planets on which intelligent life emerges.

fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.

L = The length of time such civilizations release detectable signals into space