The way that your pupils dilate, similarly, time dilates too when the speed of the object increases or if an object is subjected to an increased gravitational force. Basically, time dilation can be done in two ways.
The first is with speed. If you are sitting in an object that is going very fast. Like an airplane or a spacecraft. The faster something goes, the more would time slow down for it. Relative to a person who isn’t going as fast.
If we have to explain it with a practical example, suppose you have two clocks, we keep one clock with ourselves and put it on the ground. And we send the other clock with you on an airplane. The airplane goes around the earth once and lands back. If we then compare the two clocks, though the clocks showed the same time initially, but now the clock that you took with you on the airplane, the time it shows would be some nanoseconds behind the other.
The two clocks wouldn’t show the same time. Because one clock was travelling at a higher speed. It’s subjected to Kinematic Time Dilation. We’re not making this up.
There was an experiment in 1971. Atomic clocks were used. Because time was to be measured precisely. And it was seen that the clock that was in the airplane, the time it showed was behind that of the other clock. This was known as the Hafele Keating Experiment.
This had proved Einstein’s theory of time dilation. It doesn’t mean that time is actually slowing down for the clock, the one on the airplane.
