Gravity and Extra Dimensions

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One possible explanation of the hierarchy problem—why gravity is so much weaker than the other forces of nature—is that the force carriers of the strong, weak, and electromagnetic forces are confined to a three-dimensional brane on which we live, but the graviton is free to move in additional dimensions perpendicular to the brane. Hence, the gravitational force is diluted by the other dimensions while we perceive the other forces at full strength. (Unit: 4)