Carl Mäsak wrote: >"Far out in the uncharted backwaters of the unfashionable end of the >Western Spiral arm of the Galaxy lies a small unregarded yellow sun. >Orbiting this at a distance of roughly ninety-eight million miles is >an utterly insignificant little blue-green planet whose ape-descended >life forms are so amazingly primitive that they still think digital >watches are a pretty neat idea." -- Douglas Adams, The Hitchhiker's >Guide to the Galaxy Earth is a unique planet not because it has liquid water, but because it has large continents. The only conceivable way to create the continents was a collision between the proto-Earth and a huge atmosphere of a proto-Moon, which (in my opinion) was originally at the same place as Ceres, but was knocked into different orbit by the enormous gravity of Jupiter. The fact that the Earth orbit is nearly circular and that the Earth has captured the Moon means that there were at least 2 collisions between the Earth and the Moon. The Earth is a unique planet because the probability of these collisions was extremely low. Another proof that the Earth is a unique planet is the absence of extraterrestrial civilizations. About one percent of stars in our galaxy has planets that have liquid water. This fact suggests that life is common. Unfortunately, nearly all of this life is primitive, single cell, marine life powered by chemicals spewed from thermal vents. There is no life near the surface of their oceans because important minerals (mostly iron) are missing near the ocean surface. They don't have technological civilizations because they cannot smelt metals at the bottom of their oceans. (Can you make fire at the bottom of an ocean?) IBM's BlueGene/L supercomputer has more raw processing power than human brain. This supercomputer is used as an artificial brain by Swiss scientists who work on the Blue Brain project. I believe that by the end of this century artificial intelligence creatures will dominate the Earth. Will they use the mechanical clocks?