Kirito, think of it this way


We're currently attached to a rock that's hurtling through the universe at a very high speed, but the speed is somewhat constant so we're fine.

Fall out a building? Not the falling that kills you it's the sudden stop.

This is because of the 4 fundamental forces, Gravitation, Strong Nuclear, Weak Nuclear and Electromagnetic.

So if you're falling it's gravitation that's effecting you, and for the most part your fine. Hit the ground? That's Strong and Weak nuclear force acting which are the strongest of the forces, gravity being the weakest.

With enough energy, you can move at 0.99999999999999999999999999999999999999x the speed of light. In CERN they do this with very small particles. (I visited cern in February)
I study physics, by the way.