Saturday, January 14, 2012
John Gribbin has done his own assessment and come to the conclusion that we are alone in the Galaxy for, among other reasons.
Gribbin points to the origin of the Moon by an impact with a Mars-size body over 4 billion years ago as a pivotal and yet very dicey event. The impact itself had to avoid destroying Earth’s spin (as apparently happened at Venus) and yet excavate and launch into space enough material to form an unusually large Moon that could gravitationally anchor Earth’s axial tilt. Without such a Moon our rotation axis would wobble chaotically due to tugs by Jupiter, Venus and other bodies, and undermine the long-term climate stability conducive to the development of high intelligence and civilization.Certainly the existence of our Moon is so extraordinary that no explanation exists that fully explains it. If intelligent life is that uncommon that would mean either Earth has 2 events which have astronomical odds against or that they are related. Personally I think the variable and high tides the earth has must have greatly eased, or made possible at all, the journey of life from sea to land. There may be other effects.
Dr Bruce Cordell's estimable site has also published his assessment of the odds under the Drake Equation and comes up with a highest estimate which is only a bit more optimistic.
Initial Kepler results plus the Watson/Carter model of intelligence appear to preclude other intelligent ETs in our Galaxy unless their L’s are in the millions of years. This was attained only by our species upper limit, using Gott’s technique; the closest ETs would be ~10,000 light years away. Other high-tech civilisation timescales — species LL, nuclear doomsday, and singularity — are consistent with the Rare Earth HypothesisIf we are alone in the universe, or at least sufficiently alone that we are never likely to face competition there are philosophical consequences. We alone are the carriers of intelligence. If we destroy ourselves, through comparatively meaningless squabbles, or limit ourselves to never getting off the planet we alone on this small planet will have robbed the universe of meaning.
On the other hand this greatly increases the chance that we will succeed. The simplest answer to the Fermi question and the only one that makes sense over eons, is that intelligent scientific civilisations wipe themselves out as their power increasingly exceeds their self restraint. However if we are alone the question never arises and there is no reason to believe we will not succeed in settling as much of the universe as we wish and achieving the fullest possible understanding and mastery of it.