Quantum gravity is not a mystery that is, as yet, open to experiment. With a few exceptions such as inflationary cosmology and, quite possibly, the correct interpretation of dark energy (see Unit 11), thoughts about quantum gravity remain in the theoretical realm. This does not mean that theories of quantum gravity cannot be important and testable in some circumstances. In a given model, for instance, string theory models of particle physics make very definite statements about the origins of the mass hierarchy of fermions or the number of generations of Standard Model particles. But these problems mayalso have other solutions, insensitive to the structure of gravity at short distances; only in very few cases do we suspect that quantum gravity must be a part of the solution to a problem.
Posted on: Tue, 28 Jan 2014 15:32:37 +0000
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