It takes only a moment or a second to reach the planet 500 light-years away by spaceship. At this time, if we return to the earth, from the earth's point of view, 500 years have passed. Relatives and friends are no longer alive, and the time your body has passed is only an instant, so it has crossed into the next 500 years.

Einstein's theory of relativity says that the scale of space-time changes with the speed of the observer. When anything approaches or reaches the speed of light, time will get slower and slower, and when it reaches the speed of light, time will stagnate. This is the time dilation effect.

Extended data:

The fastest manned aircraft that humans have reached is:

1, Voyager 1, about17 km/s.

2. New horizon number, about 21km/s.

3. Parker probe: the goal is to go to the sun orbit of the inner planetary ring and run at a speed of more than 200KM/S at the perihelion under the condition of conservation of angular momentum!

4. Highest theoretical speed: Break through the Star Shooting Program, which aims to send a micro detector to proxima centauri Centauri orbit, and the highest speed can reach about 20% of the speed of light.

The distance of a light year is not difficult to calculate, because the speed of light has been determined as 299,792,458 m/s, but the time of one year is actually based on a Julian year, that is, 365.25 days, 86,400 seconds per day, and the total number of seconds is 365,438+0,557,600 seconds. Then a light-year is a very simple multiplication:

1ly = 299792458× 31557600 = 9460730472580800 meters.