In the presence of gravity, both space and time are affected. Space can become curved, and time can experience a phenomenon known as time dilation. However, the nature of these effects differs.
When we say that space becomes curved in the presence of gravity, we mean that the geometry of spacetime is altered. Massive objects, such as stars or planets, create a gravitational field that curves the fabric of spacetime around them. This curvature affects the path of objects moving through space, causing them to follow curved trajectories.
On the other hand, time dilation refers to the stretching or slowing down of time in a gravitational field. It is a consequence of the curvature of spacetime. When an object is in a strong gravitational field or moves at high speeds, the flow of time for that object appears to slow down relative to an observer in a weaker gravitational field or at rest.
The reason time dilation occurs is linked to the principle that the speed of light is constant in all reference frames. In the presence of gravity, the curvature of spacetime alters the path that light takes. As a result, the path of light is "warped" or bent by the gravitational field. However, the speed of light itself remains constant.
Since the speed of light is constant, time dilation occurs to maintain the constancy of the speed of light. When an object is in a strong gravitational field, the curvature of spacetime affects the flow of time, causing it to slow down. This time dilation compensates for the warped path of light, ensuring that light continues to travel at the same speed.
In summary, while light is influenced by the curvature of spacetime and follows a warped path in the presence of gravity, time dilation occurs to maintain the constancy of the speed of light. The slowing down of time is a consequence of the curvature of spacetime and the need to preserve the fundamental properties of light.