Tuesday, November 28, 2006

The following very short article relates to the development of planets around stars, about which I made a post some time ago. I'll quote the whole article, which appeared on globeandmail.com.

Planets really made from dust
Globe and Mail Update
Monday, October 09, 2006

Floating discs of debris do indeed turn into planets, and now the world finally has evidence to prove it.
Scientists analyzing data from the Hubble Space Telescope have at last confirmed the long-held belief put forward by philosopher Emmanuel Kant more than 200 years ago.
Until now, astronomers have detected more than 200 extra-solar planets and have seen many debris disks around young stars, but they have yet to observe a planet and a debris disk around the same star.

Again, this does not relate directly to biological evolution, but it shows that the universe incorporates evolution even in its non-biological history. This is a different meaning of evolution from the evolution referred to in natural selection. This is the more general notion that relates to things which change progressively over time and don't change back.

The idea that planets can form from space dust has been around for a while, as the article notes. Over time, more and more evidence has been produced and this process continues. Now we can safely assert that there are hundreds of billions of hundreds of billions of stars in the universe, and many, if not most, of these have planets around them.

The number I gave above is not just hyperbole of the sort associated with Carl Sagan. The accepted round number for stars in our galaxy is 100 billion. And an all sky survey that counted galaxies reached a similar number of galaxies in the universe. Some of these are smaller than the Milky Way but many are much larger. So a hundred billion hundred billion is accurate, to a few orders of magnitude.

We cannot yet determine if any of these other planets has life of any sort, let alone complex, possibly intelligent, organisms. But if we accept that the universe is a well-ordered place, with the same laws operating here as anywhere else, we can only conclude that there should be a great number of planets with life. Considering the number of animals on earth which have similar intelligence and social lives as humans (apes, dolphins, whales, and elephants), I think it very unlikely that we are the only species in the universe contemplating these same questions.

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