What is the theory of relativity?

The theory of relativity is a fundamental framework in physics developed by Albert Einstein that describes the relationship between space, time, and gravity. It is actually composed of two related theories: special relativity and general relativity. Special relativity, introduced in 1905, deals with objects moving at constant speeds, especially those moving close to the speed of light. It established that the laws of physics are the same for all observers moving at constant speeds relative to each other, and that the speed of light is always constant regardless of the observer’s motion. One of its key results is that time and space are not absolute — time can slow down and lengths can contract depending on how fast an object is moving relative to someone else. General relativity, published in 1915, expands on this by describing gravity not as a force but as a curvature of spacetime caused by mass and energy. Massive objects like planets and stars bend the fabric of spacetime, and this curvature affects the motion of other objects, which we perceive as gravity. This theory has been confirmed through many experiments and explains phenomena such as the bending of light around massive objects and the expansion of the universe. In essence, the theory of relativity revolutionized our understanding of time, space, and gravity, providing the foundation for much of modern physics and cosmology.