In a Scientific American essay based on their new book A Grand Design , Stephen Hawking and Leonard Mlodinow are now claiming physicists may never find a theory of everything. Instead, they propose a "family of interconnected theories" might emerge, with each describing a certain reality under specific conditions. Most of the history of physics has been dominated by a realist approach. Scientists simply accepted that their observations could give direct information about an objective reality. In classical physics, such a view was easily defensible, but the emergence of quantum mechanics has shaken even the staunchest realist. In a quantum world, particles don't have definite locations or even definite velocities until they've been observed. This is a far cry from Newton's world, and Hawking/Mlodinow argue that - in light of quantum mechanics - it doesn't matter what is actually real and what isn't, all that matters is what we experience as reality. As
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