The Anthropic Principle: Why Are the Laws of Physics So … Convenient?

Eternal Inflation The laws of nature that we have discovered work wonderfully to explain phenomena from atomic transitions to colliding galaxies. But those laws include many specific numbers that seem completely arbitrary: the masses of different particles, the strength of the forces holding atoms together, and so on. Our physical theories don’t explain why these constants of nature have the values they do, but we can show that if some of them were even slightly different then no complex structures could exist in the universe. So why do these numbers seem to have exactly the values we need in order for us to exist?

One possible explanation is the “anthropic principle,” which posits that in other parts of the universe these numbers take on other values. We observe the values we do because only regions with those values can evolve creatures capable of measuring them. In this talk I’ll explain the anthropic principle, discuss some of the many misconceptions about it that appear in popular accounts, and talk about what conditions would have to be met in order for this idea to work.

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