What is the thought experiment that proves the relativity of time intervals?

The experiment consists in the fact that the time interval between two events depends on the frame of reference, that is, it is relative. The proper time r is always less than the time interval between the same events, measured in any other frame of reference. This effect is called relativistic time dilation. Time dilation is a consequence of the invariance of the speed of light.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.