Relativistic speed

So, you know how you can run really fast, and when you do, everything around you seems to be moving slower than you? Well, that's kind of like what happens when things go really, really fast, except it's not just you running, it's things like electrons and light.

You see, the faster things go, the more they warp the space around them and the slower time moves for them. It's kind of like if you were in a car going really fast, and you looked at someone outside walking, they'd seem like they're moving really slowly.

But when things go REALLY fast, like almost as fast as the speed of light, weird things start to happen. Time seems to slow down a lot, and things get shorter and heavier. And if something were to go at the speed of light, time would pretty much stop and it would become infinitely heavy.

So basically, relativistic speed is when things go really, really fast and strange things happen to them, like time slowing down and objects getting heavier.