Question: What is the theory of relativity?

Lyndsey Fox answered on 15 Jun 2011:

Oh wow seriously tough question! I’m probably definately not the best person to answer this. I don’t really fully understand it myself but this is how it was explained to me:

Einstein observed that the passage of time, which everyone had always simply assumed is constant and unchanging is not: it’s the speed of light that is.

So the theory of relativity shows how the speed at which time happens is liable to change;
that space and time are not discrete entities: time and space and motion (ie, movement through space) collapse into a fourth dimension, in which all act on each other.
So you can’t say “now” without saying “here” and “how fast”.

If you move fast enough through space, the observations that you make about space and time differ somewhat from the observations of other people, who are moving at different speeds.

For example:
Imagine you are on a space ship, and you travel at (close to) the speed of light in space, when you get back to earth, 10 years have passed and people on earth have aged 10 years but you have only aged a few days…

…Basically, due to the effects of relativity, the faster you travel, the more your spaceship’s timeclock slows down. Inside your spaceship, your perception of reality slows down to match the slowdown of the clock, so your time feels normal in every way to “normal time”.
But if an outside observer NOT moving at the speed of light could somehow peek in your spaceship’s window and watch the ship’s timeclock, he would say your clock is running slow compared to his, which is running normal to him. To him it would appear to be running so slowly that your clock would only advance a few days over a ten year period. That’s the effect of time dilation, one aspect of relativity.

If that didn’t make any sense think of it like this: If you put your hand on a hot pan, a second feels like an hour, if you put your hand on a hot woman an hour feels like a second. It’s all relative lol.