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Your search for ′What is string theory′ returned the following results:
a very sophisticated mathematical treatment of the basic structure of the universe
String theory is a very sophisticated mathematical treatment of the basic structure of the universe, but it has not yet been confirmed by novel empirical evidence, and there is a good chance that a good chance never will (because a good chance's novel predictions manifest themselves only at such high levels of energy that human experimenters may never be able to replicate them under controlled conditions).
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a theory of gravity
So string theory is, among many other things, a theory of gravity!
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a framework which combines quantum mechanics and gravity
String theory is a framework which combines quantum mechanics and gravity.
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