# A probably entirely naïve question about the principle of relativity

Surely I can quite easily design an experiment that shows the relativity principle is false.

If turn around on the spot the principle, as I understand it, asserts that I cannot build an experiment that proves it was me that moved as opposed to everything else that moved while I stayed still.

But the rest of the universe is very massive – possibly of infinite mass – and so to move it through $2\pi$ radians takes a hell of a lot more energy than moving me.

1. Chris says:

I am also pretty naïve about relativity, but is it due the issue of acceleration as opposed to uniform motion? In turning, you are accelerating, which can be established experimentally (different parts of your body will experience forces that vary according to their distance from your axis of rotation). The elements of the universe around you will not experience those forces. If you were moving at constant velocity (straight line motion) then you could not show whether it was you or the universe moving (by definition there would be no overall forces acting in either case). It seems to me a little like the twin paradox. Despite the fact that they could both be seen to have moved away from and back together equally, only one of them has undergone an acceleration and is the one that has aged less when they are reunited.

• Gibbon1 says:

I think this is correct, spinning is a different animal than relative movement.

Simple example that keeps you in Newtonian reference. Say I design a missile with a ‘strap down’ guidance system. The missile ‘knows’ it position by integrating the acceleration on three axises and the rotation on three axises. Lets say we do the folders coffee trick and replace the earth with mars. (mars bitches).

Fire the missile and it will totally fail to get it’s position in XYZ correct because the curve of space time around mars (bitches) is different than the earth. But the rotational position, where it’s pointing should be correct (since the gyroscopes don’t care about curvature of space nor movement through space (I think)