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In Section XXII it has been already mentioned that according to

the general theory of relativity, a ray of light will experience

a curvature of its path when passing through a gravitational

field, this curvature being similar to that experienced by the

path of a body which is projected through a gravitational field.

As a result of this theory, we should expect that a ray of light

which is passing close to a heavenly body would be deviated

towards the latter. For a ray of light which passes the sun at a

distance of Δ sun-radii from its centre, the angle of deflection

(α) should amount to

image053

It may be added that, according to the theory, half of this

deflection is produced by the Newtonian field of attraction of

the sun, and the other half by the geometrical modification

("curvature") of space caused by the sun.