
490 Classical Mechanics
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using the equivalence principle, we conclude that in a gravitational eld, light will not travel along
a straight line, but its path will be curved (Figure 14.14b).
Although in the context of Newtonian gravity, we do not expect that gravity will inuence the
propagation of light, Newton somehow made a non-relativistic quantitative calculation of the bend-
ing of light in 1801. He got half the value given by the general relativity theory. We now make a
semiclassical calculation, which suffers from a foundation built upon a Euclidean space–time. Our
calculation is based on the following assumptions ...