Why do fighter pilots get paid so much to sit down?

Gravity may be the big force in the world most of the time - but a set of wings and an internal combustion engine can outdo it sometimes - watch this Red bull air racer:

  

The reason he's occasionally pulling a funny face and grunting isn't because he's pleasuring himself, or forgot to visit the men's room before he took off*. It's because the sharp turns his plane is making subject him to centripetal force - up to eleven gravities of it. 

 Centripetal force-  the stuff that's making everyone feel sick on this ride. And it's a force that can throw vomit a long way too....

Imagine if your eyeballs suddenly weighed eleven time what they normally do - it'd feel like they were being sucked out of your head.

Imagine if your poo did... no, don't.

Why should that happen? 

It works like this: If nothing's acting on them then objects either stay still, or go in a straight line with a fixed speed (Newtons first law). That's just one of them thar rules of the universe.

For something to follow a curve some force has to be pushing on it. The centripetal force making the plane turn is coming from its wings and engine, and being transmitted to the pilot through his seat. His body doesn't have its own wings or engine, so it's resisting that force, trying to follow the rules and go in a straight line. 

And because the curves he's pulling are so tight his body is resisting a lot - eleven gees worth of stubborn.The stubborn resistance to centripetal force is sometimes called centrifugal force, but it isn't really there, it's just a reaction to the centripetal force.

Confused yet? Watch what it did to Jeremy Clarkson (Britain loves watching this man suffer):

* I can't be certain of either statement, I just don't want to think about it....