There is no absolute, or "same," time
and space. This means time and space are different for everyone! How you experience events in time and space depends on TWO important things:
Where you're looking from. Imagine you're sitting on a
fast-moving train. You see your friend moving by you; your friend sees you moving by him.
How fast you're moving compared to the speed of light. Imagine you are still on the train
and two lightning bolts flash one in front of the train, the other behind it. If your friend sees them flash at the same time, you'll see them flash
at different times. Why? Because you're moving toward the light of one bolt and away from the light of the other.
been working on a thought experiment. Einstein and others have used them to try to explain how the universe works.
To perform a thought experiment, you don't need a
laboratory or machines just your imagination! Once, when someone asked Einstein where his laboratory was, he pointed to his pen.