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Published on Mar 17, 2017
Matter is organized and held together by four forces: electromagnetism, weak and strong nuclear forces, and gravity. Each is built around a peculiar inner symmetry that fundamental particles seem to have. Depending on the type of symmetry and on the number of matter particles, at smaller distances such forces can get stronger or weaker, or even display scale invariance (just like in fractals). Extrapolating our current data to very small scales suggests the presence of a larger symmetry, which would underlie a single force unifying electromagnetism and the nuclear forces. Gravity behaves differently; unifying it with the other three seems to require the emergence of new physics at even smaller scales. One possibility is string theory, which predicts additional space dimensions whose shape would explain the forces and matter particles we observe, thus giving an elegant geometrical origin to the fundamental properties of the Universe's building blocks.