A light beam that is bent by gravity, as predicted by Einstein's general theory of relativity, would behave differently from a light beam that travels through an empty void with no gravitational influence. Here are the key differences:
Path curvature: In the presence of a gravitational field, such as near a massive object like a star or a black hole, light follows a curved path due to the curvature of spacetime. This bending of light is known as gravitational lensing. In contrast, in an empty void without gravity, light would travel in a straight line.
Deflection angle: The amount of bending experienced by a light beam in a gravitational field depends on the strength of the gravitational field and the proximity to the massive object causing it. The greater the mass and the closer the light beam passes to the object, the larger the deflection angle. In an empty void, without any gravitational influence, light would continue to travel in a straight line without any deflection.
Time dilation: According to general relativity, gravity affects the passage of time. In the vicinity of a massive object, time runs slower compared to regions of weaker gravity. This gravitational time dilation can cause light to experience a shift in frequency or wavelength, known as gravitational redshift or blueshift, depending on whether it is moving away from or towards the gravitational source. In an empty void without gravity, there would be no time dilation effect on light.
Gravitational time delay: Gravity can also cause a delay in the propagation of light. As light travels through a gravitational field, it takes a longer path due to the curvature of spacetime, resulting in a time delay compared to the light that traveled in a straight line. In an empty void without gravity, there would be no such time delay.
These differences in the behavior of light beams in the presence or absence of gravity have been confirmed through various observational tests and experiments, such as the deflection of starlight by the Sun during a solar eclipse. These phenomena provide evidence for the validity of Einstein's general theory of relativity and the influence of gravity on the path of light.