So this seems to be a perfectly ordinary three-dimensional world.

There are three ways I can go.

I can go forwards and backwards, side to side, up and down.

There can't be anything much more than that, can there?

So if I want to go up the tower, for example, over there, I go sideways, I go forwards, and I go up.

Seems to be the only possibilities.

But not necessarily.

If we could conjure up an extra dimension, it could explain how you get supergravity at the tiny scale.

Because, although gravity seems strong in our everyday lives, it's actually pretty feeble.

Gravity is a puzzle.