According to the theory of special relativity, time dilation occurs when an object or observer is moving at relativistic speeds relative to another object or observer. Time dilation means that time appears to pass more slowly for the moving object or observer compared to a stationary reference frame.
In the scenario you described, where someone travels through space at a very high speed (approaching the speed of light) and returns to Earth 10 years later from their perspective, the situation would be different for the observer on Earth. Due to time dilation, the observer on Earth would have experienced more time passing than the traveler.
From the perspective of the traveler, they would perceive that only 10 years have passed, as their own time is dilated or stretched. However, when they return to Earth, they would find that more time has passed for the people on Earth. The amount of time that has passed for the people on Earth would depend on the exact speed of the traveler relative to Earth and the duration of their journey.
This phenomenon is a consequence of the relativistic nature of time and is a well-established aspect of special relativity. It has been experimentally confirmed through various experiments involving high-speed particles and atomic clocks.