The Anthropic Cosmological Principle and Related Issues

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The anthropic cosmological principle asserts that the laws, constants and basic structure of the universe are not completely arbitrary. Instead they are contrained by the requirement that they must allow for the existence of intelligent observers, ourselves.

Example: Why is the visible universe about 15 Billion light years in diameter? Because that means the universe is about 15 billion years old. Our sun is at least a second generation star because it contains Carbon, Oxygen, Silicon and other elements. It had to get them from earlier stars that had exploded--they were not available just after the big bang (which could only have produced Hydrogen and Helium). Hence the sun as we know it could not have existed much earlier in the history of the universe. Since we in turn require those elements, we could not have existed in a much earlier phase of the universe. You also have to allow a few billion years for evolution. We see a universe that is 15 billion light years across because the universe had to grow to that size to permit us to exist. We could not, incidentally, observe a universe that was a lot older, since by that time the stars will have burned out and there will be no available energy to support life. Many other examples are discussed in the following references.

There are lots of other facts in physics, astronomy, and chemistry, that can be interpreted in this manner. You can argue that this is all coincidence, and some of these observations have been referred to as "cosmic coincidences". You can also argue that this is obvious--nothing else would be possible. The subject is very controversial.

One aspect of this is that the Principle asserts that there is something special about our place in the universe. The example above shows that we must live in a particular segment of cosmic history. This goes against the general trend of science since Copernicus; that there is nothing special about our place. This makes a lot of scientists uncomfortable, but I think it is hard to dispute.

It may be that all of this is unnecessary, and that the cosmic coincidences can be derived from a physical theory, such as superstrings. This is the view of "The Beginning of the End of the Anthropic Principle". Thanks to Bernard Leong for bringing this paper to my attention.

Theologically, the anthropic principle has led to a revival of the argument from design, which had lost its intellectual respectability when Darwin came along. I think the mainstream theological community was taken by surprise when the physicists came up with this. John Polkinghorne has some good discussions of the theological issues. See, for example, The Faith of a Physicist (Polkinghorne was a prominent theoretical physicist before becoming an Anglican priest).

Fundamentalists with intellectual pretenses also like the anthropic principle, but they conveniently omit the relationship between the human evolutionary time scale (billions of years) and that of the universe (also billions).

The Future of the Universe and Life.

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©1996, 2002 by Glenn T. McDavid
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