Friday, September 28, 2007

Anthropic Principle

We should take into account the constraints that our existence as observers imposes on the sort of universe that we could observe.

"There exists one possible Universe 'designed' with the goal of generating and sustaining 'observers.' "

"Observers are necessary to bring the Universe into being."

"An ensemble of other different universes is necessary for the existence of our Universe."

"Weak" Anthropic Principle:

Roger Penrose explains the weak form:

The argument can be used to explain why the conditions happen to be just right for the existence of (intelligent) life on the earth at the present time. For if they were not just right, then we should not have found ourselves to be here now, but somewhere else, at some other appropriate time. This principle was used very effectively by Brandon Carter and Robert Dicke to resolve an issue that had puzzled physicists for a good many years. The issue concerned various striking numerical relations that are observed to hold between the physical constants (the gravitational constant, the mass of the proton, the age of the universe, etc.). A puzzling aspect of this was that some of the relations hold only at the present epoch in the earth's history, so we appear, coincidentally, to be living at a very special time (give or take a few million years!). This was later explained, by Carter and Dicke, by the fact that this epoch coincided with the lifetime of what are called main-sequence stars, such as the sun. At any other epoch, so the argument ran, there would be no intelligent life around in order to measure the physical constants in question-so the coincidence had to hold, simply because there would be intelligent life around only at the particular time that the coincidence did hold!

The Emperor's New Mind, Chapter 10

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