The bending of spacetime and the existence of time dilation are consequences of the fundamental principles of Einstein's theory of general relativity. In this theory, gravity is not considered as a force acting at a distance, but rather as the curvature of spacetime caused by the presence of mass and energy.
According to general relativity, massive objects like planets, stars, and galaxies create a gravitational field by curving the fabric of spacetime around them. This curvature affects the motion of other objects, causing them to follow curved paths or orbits around the massive objects. The more massive an object is, the greater the curvature of spacetime it produces.
As for time dilation, it arises due to the relationship between gravity and the geometry of spacetime. In regions with a stronger gravitational field, spacetime is more severely curved. When an observer is located in such a gravitational field, the curvature of spacetime affects the passage of time.
To understand time dilation, imagine two observers—one in a weaker gravitational field and the other in a stronger gravitational field. The observer in the stronger gravitational field experiences a more significant curvature of spacetime, causing time to pass more slowly compared to the observer in the weaker gravitational field.
In addition to gravity, relative motion also contributes to time dilation as described by the special theory of relativity. When two observers are moving relative to each other at different speeds, they perceive time passing differently. This is known as velocity-induced time dilation.
In summary, the bending of spacetime and the existence of time dilation are inherent consequences of the way mass, energy, and motion affect the geometry of spacetime, as described by the principles of general and special relativity. These effects have been supported by numerous experimental observations and are fundamental to our understanding of the universe.