So, if I travel in a ship at light speed in a line from earth to space for 10 minutes. Than turn around and travel back at light speed for 10 minutes. To earth time, I would be gone 20 minutes... But everywhere I read people are saying that earth will be in the future by the time I come back. But I only raveled 20 minutes since light goes so fast. So why would earth be in the future? I understand that on the spaceship time stops. So in reality I should not of aged those 20 minutes while the people on earth have aged 20 minutes.. So how come when i research. Everyone saying that thousands of years would have went by.. But in reality light moves fast. And if time stopped. How does light go back and forth so fast if time is really stopping? Seems like light it self would stop if time stops right? Because it light is still moving that fast and can come back to earth in 20 minutes and observe the same earth as when the light left. Why does it change if a human is on board observing?