Time Dilation, Multiple Earth's?

Question

I was reading about time dilation and suddenly a question raised in my mind. (This might be a misconception but please do correct me if I am wrong)

I read that if we travel near to the speed of light,time will move slow.

My question is this.

Suppose a rocket is traveling from earth at a velocity near to light .Another rocket traveled to mars with ordinary rocket speed and suppose after traveling one year, both rockets had reached back to earth.So according to time dilation when the first one reaches earth, let's say that 50 years has passed on Earth. So the people on the first rocket will live on Earth after 50 years. But the second rocket did not went in the speed of light and will happen to see the same earth after 1 year. But how can both rockets see different versions of Earth at the same time?

There is big chance that this question is wrong, but please explain and correct me about time dilation.

Answer 1

Your statement "after traveling one year, both rockets had reached back to Earth" means different things to the two ships, because the clocks on the two ships keep time at different rates. After the fast ship has travelled one year according to the fast ship's clock, a clock on Earth will say that 50 years have gone by. But if the slow ship returns after a year has passed on the slow ship's clock, it will arrive on Earth after only roughly one year has passed according to a clock on Earth.

So if the two ships each travel one year according to their own clock, they won't arrive to two different Earths at the same time, because, according to a clock on Earth, the slow ship arrives back on Earth 49 years earlier than the fast ship does.

Answer 2

Your statement "I read that if we travel near to the speed of light,time will move slow." misses some important information. "Moves slow" relative to what? It doesn't say it, but it makes people think there is some universal time to measure the perception of time relative to. There is not. An observer in the lab (at rest in his own frame) sees fast moving clocks running slow. But also observer primes, traveling with those clocks will see the lab clocks running slow.