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Why is the universe the way it appears? Some scientists think that our very existence provides the answer. To them, many of the physical properties of the universe seem finely tuned for producing life. For instance, if the relative strengths of the four fundamental forces were slightly different, stars might never have formed and life as we know it would have been impossible. Or if the universe had expanded slightly faster than it did, matter would have spread out too quickly to coalesce into any significant objects. Conversely, if the expansion had been just a little slower, the universe would have already collapsed back into a “Big Crunch.”
These and other cosmic “coincidences” led some scientists to speculate that the universe is the way it is because we are here to observe it. This anthropic principle has two basic versions, the weak and the strong. The weak version, developed by Robert Dicke in the early 1960s, states that in a large universe, intelligent life can exist only during a narrow window of time. We shouldn’t be surprised at the universe we see because we could never be around to view it at a significantly different time. The strong anthropic principle goes much further. Proposed by Brandon Carter in the late 1960s, it states that among all the possible universes that could exist, only a special few have the right conditions that could give rise to intelligent life. The cosmic coincidences are then not some fundamental aspect of the way the laws of physics operate, but rather a prerequisite for the development of life. If the strong anthropic principle is true, then some would argue that the universe was designed with a purpose. If it is false, then a future “theory of everything” should be able to explain why the seeming coincidences that created life really are not. |
