According to the theory of relativity, specifically the theory of special relativity, time dilation occurs when an object is in motion relative to another object. Time dilation means that time appears to pass slower for the moving object compared to a stationary observer.
If you were to travel near the speed of light and then turn around and come back towards Earth, you would experience time dilation. As you approach the speed of light, time for you would appear to slow down relative to an observer on Earth.
From your perspective, you would perceive time passing normally on your spaceship, but time on Earth would appear to be moving much faster. This means that while you might have only aged a few years during your journey, many years or even decades might have passed on Earth.
When you turn around and come back towards Earth, the time dilation effects would reverse. Now, from Earth's perspective, time on your spaceship would appear to be moving slower, while time on Earth would seem to be passing at a regular pace. As a result, when you return to Earth, you may find that a significant amount of time has passed, possibly much longer than the duration of your journey.
This phenomenon is known as the "twin paradox," where one twin who travels at high speeds ages less than the other twin who remains on Earth. However, it's important to note that the time dilation effects become significant as you approach the speed of light, which is an extremely challenging feat for any object with mass to achieve.
In reality, achieving such speeds and conducting experiments near the speed of light is currently beyond our technological capabilities. The effects described here are based on theoretical predictions from the theory of special relativity.