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Some Consequences

The formulation of Einstein's equation we have given is certainly not the best for most applications of general relativity. For example, in 1915 Einstein used general relativity to correctly compute the anomalous precession of the orbit of Mercury and also the deflection of starlight by the Sun's gravitational field. Both these calculations would be very hard starting from equation (2); they really call for the full apparatus of tensor calculus. However, we can easily use our formulation of Einstein's equation to get a qualitative -- and sometimes even quantitative -- understanding of some consequences of general relativity. We have already seen that it explains how gravity attracts. We sketch a few other consequences below. These include Newton's inverse-square force law, which holds in the limit of weak gravitational fields and small velocities, and also the equations governing the big bang cosmology.


© 2006 John Baez and Emory Bunn