The difference between "bending" and "curving" of light under gravity arises from the different descriptions of gravity provided by Newtonian physics and Einstein's theory of general relativity (GR).
In Newtonian physics, gravity is described as a force of attraction between massive objects. According to Newton's laws, light is not affected by gravity because it is considered to be composed of massless particles called photons. In this framework, light travels in straight lines unless it encounters a medium or an object that causes it to deviate from its original path. Therefore, the concept of light bending under gravity does not exist in Newtonian physics.
On the other hand, according to general relativity, gravity is not seen as a force but as a consequence of the curvature of spacetime caused by massive objects. In Einstein's theory, all forms of energy, including light, are influenced by the curvature of spacetime. When light passes through a gravitational field, it follows a path that is curved by the geometry of spacetime itself. This phenomenon is known as gravitational lensing.
The consequences of this difference are significant. In general relativity, the bending or curvature of light under gravity has been confirmed through experimental observations and is a key prediction of the theory. Gravitational lensing has been observed and measured in various astrophysical contexts, such as the deflection of starlight around massive objects like the Sun, the distortion of distant galaxy images by intervening clusters of galaxies, and the formation of multiple images of a single source due to strong gravitational fields.
The effect of gravitational lensing has practical implications as well. It allows astronomers to study and map the distribution of mass in the universe, including the presence of invisible dark matter. Gravitational lensing can also magnify and distort the appearance of distant objects, enabling us to observe and study otherwise faint or obscured astronomical sources.
In summary, the distinction between "bending" and "curving" of light under gravity arises due to the contrasting descriptions of gravity in Newtonian physics and general relativity. While Newtonian physics does not account for light bending, general relativity predicts and explains the phenomenon through the curvature of spacetime. This distinction has profound consequences for our understanding of gravity and the study of the universe.