Mirror image inversion in the 4th dimension.

[Rocks64]

It is relative. If I were to be flipped in 4D into a mirror image of myself: 1) I would remain unchanged to myself, but it would appear that the world was backwards. 2) Anyone observing me would see me turned into a mirror image of who I once was.

 

[tade]

Not any weirder than looking out the train window and thinking that it could just as well be the landscape moving past. The unexpected bit is finding that there actually is an experimental test that can detect chirality reversal.

The concept of relative motion is easy to grasp, but relative chirality? That's mind-blowing.