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In the first place, it can be compared with the reality. Although

a detailed examination of the question shows that the curvature

of light rays required by the general theory of relativity is

only exceedingly small for the gravitational fields at our

disposal in practice, its estimated magnitude for light rays

passing the sun at grazing incidence is nevertheless 1.7 seconds

of arc. This ought to manifest itself in the following way. As

seen from the earth, certain fixed stars appear to be in the

neighbourhood of the sun, and are thus capable of observation

during a total eclipse of the sun. At such times, these stars

ought to appear to be displaced outwards from the sun by an

amount indicated above, as compared with their apparent position

in the sky when the sun is situated at another part of the

heavens. The examination of the correctness or otherwise of this

deduction is a problem of the greatest importance, the early

solution of which is to be expected of astronomers.[16]