General Relativity, formulated by Albert Einstein in 1915, is one of the most profound theories in physics. It describes gravity not as a force, but as the curvature of spacetime caused by mass and energy. This revolutionary concept changed our understanding of the universe, from the motion of planets to the behavior of black holes and the expansion of the cosmos.
In flat spacetime, objects move in straight lines. But when mass is present, it curves the fabric of spacetime itself. This curvature guides the motion of objects, creating what we perceive as gravitational attraction. The more massive an object, the greater the curvature it creates.
One of the most fascinating predictions of General Relativity is time dilation. Time runs slower in stronger gravitational fields. A clock near a massive object like Earth runs slower than a clock far away. This effect has been measured with atomic clocks and is essential for GPS satellite accuracy.
黑洞代表了时空扭曲的极端情况。在事件视界处，时空曲率变得如此剧烈，以至于逃逸速度超过了光速。史瓦西半径定义了这个不归点。光线在黑洞周围发生剧烈弯曲，有些被困在光子球面的不稳定轨道上。