X-Message-Number: 5537 Date: Wed, 3 Jan 1996 22:04:36 -0800 (PST) From: Doug Skrecky <> Subject: Re: nightmares In message #5519 wrote: >You want nightmares? I'll give you nightmares. >A couple of people recently on Cryonet (Clark & Metzger?) have >speculated on possible dark futures, one being related to the >apparent absence of superhuman extraterrestrials. >I have commented on this many years ago, as has Mike Hart in a >couple of his books. it is exceedingly difficult to account for >the absence of such superhuman interveners in any way consistent >with BOTH optimism about our future and the notion that intelligent >and technologically advanced races have preceded us. Unless we are >the first, it seems hard to avoid pessimistic conclusions about the >fate of technologically advanced peoples. Frank Tipler has advanced the view that we are alone because we are the first technologically advanced civilization to arise in our galaxy. ETI's never killed themselves off because thery never existed. The December issue of Equinox magasine contains an article entitled "Earth: There's No Life Like It" written by Terrence Dickinson, which outlines a number of reasons why the survival of life on earth can be regarded as an extremely low probability fluke. One fact that I had not heard of before is that in computer simulations in which the earth & moon are removed destabilises the orbits of the other inner planets. Since a stable orbit is needed to restrict surface temperatures between the freezing and boiling points of water the stable orbits of the inner planets might be regarded as being a very low probability situation, equivalent to flipping a coin and having it come up on its edge. This argument has not yet been fully developed and further computer simulations will be needed before the low probabilities of stable orbits can be confirmed. There exist a number of other apparently rare conditions upon which the development of intelligent life over billions of years is dependant on. These include the requirement of a Jupiter sized planet in the outer solar system to act as a shield against comets. Without Jupiter I have heard estimates of the time interval between comet hits on earth similar to the one which occurred 65 million years ago and wiped out the dinosaurs (and to comet Shoemaker-Levy 9 which just hit Jupiter!), of about every thousand years or so. No Jupiter = no intelligent life on earth. Astronomers have the capability to detect Jupiter type planets and have failed to find any. Jupiter seems to be a cosmic fluke. The massive collision between a mars sized body and the proto-earth which just happened to form a large moon in a close orbit around the earth has also been regarded as a very low probability event. Without a large moon to stabilize the orbit of the earth, the green planet would be an ice planet. No moon = no intelligent life on earth. If the earth were slightly more massive it would be like its sister planet Venus, which is a hellish inferno with surface temperatures above the melting point of lead. If an earth of mass were just 1% closer to the sun it would also be a hellish inferno. If the earth were slightly farther away from the sun it would have developed into an ice planet. Earth is just the right size and is in just the right place. Another cosmic coin flip landing on its edge. Finally after billions of years of placid existence the sun is alas soon to leave the main sequence and begin its slow increase in size to become a red giant. Original estimates of how much time life has left on earth ran to just 100 million years - that's all. However more careful consideration has upped this figuare somewhat. When one considers that evolution was basically at a standstill till just 600 million years ago (the Cambrian explosion) we might conclude that we just barely made it! Coin flips landing on their edge: 1. stable orbits of inner planets 2. Jupiter in outer solar system 3. earth has very large moon 4. just the right mass at just the right distance from the sun 5. Cambrian explosion started just in the nick of time. Rational conclusion: We are very, very lucky to be here. Our's is probably the first and only technologically advanced civilization to exist in our galaxy. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=5537