Searching for Gravity's Hidden Strength

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Science  31 Oct 2003:
Vol. 302, Issue 5646, pp. 795-797
DOI: 10.1126/science.1090003

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Gravity is by far the weakest of the four known forces. The gravitational attraction between two protons is 35 orders of magnitude weaker than their electromagnetic repulsion. The weakness of gravity may not be an intrinsic property, however, but may result from the propagation of gravity in extra spatial dimensions. In his Perspective, Feng describes the search for strong gravity and extra dimensions that is now being pursued on many fronts--from tabletop probes of Newtonian gravity to searches for microscopic black holes in kilometer-scale cosmic ray detectors. Upcoming experiments will either exclude this explanation of the weakness of gravity or find evidence for a radically new view of spacetime.