Final answer:
Time dilation occurs in orbits in the Schwarzschild metric, where both space and time are distorted near massive objects like black holes.
Step-by-step explanation:
According to general relativity, time dilation occurs in orbits in the Schwarzschild metric. Near a massive object like a black hole, both space and time are distorted. The Schwarzschild radius, also known as the event horizon of a black hole, represents the point where time dilation becomes significant. For example, in satellite orbits 20,000 kilometers above Earth, the orbiting clocks tick about 45 millionths of a second faster than they would on Earth, resulting in a net advance of about 38 microseconds per day. These relativistic effects must be taken into account to avoid navigation errors.