The deflection of the first beam of light in the gravitational field is simply that light is also a matter, so it will also be affected by gravity, and deflection will occur at this time. The premise is that such an object must be very large to have an impact on light, and only a large enough object can deflect light.

The second gravitational redshift, in short, is that the frequency of electromagnetic waves will become smaller due to the influence of gravity. At first, this could not be verified by experiments, and it was not until 1959 that the experimental conditions were available.

The third is the precession of Mercury's perihelion. The main reason is that Mercury will be influenced by other planets. Among the three major effects, this is the first proven theory.

Development process:

1905, Einstein published a paper on the influence of gravity and acceleration on light in special relativity, and the prototype of general relativity began to take shape.

19 12 years, Einstein published another paper to discuss how to describe the gravitational field in geometric language. At this point, the kinematics of general relativity appeared.

By 19 15, Einstein's field equation was published, and the dynamics of the whole general theory of relativity was finally completed.