Physicists are learning to live with Einstein's 'fudge factor', the cosmological constant. New thinking attempts to tie its value to other fundamental constants in elementary particle physics. The recognition, in the light of observational data, that Einstein's infamous cosmological constant might not be zero has changed almost everything about the way we think about the Universe, from reconsidering its origin to re-evaluating its ultimate future. But perhaps the most significant change in cosmological thinking involves a new willingness to discuss what used to be an idea that was not normally mentioned in polite company: the anthropic principle. This idea suggests that the precise values of various fundamental parameters describing our Universe might be understood only as a consequence of the fact that we exist to measure them. To paraphrase the cosmologist Andrei Linde, "If the Universe were populated everywhere by intelligent fish, they might wonder why it was full of water. Well, if it weren't, they wouldn't be around to observe it!".
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