| GP is right. If aliens don't know about CP violation, there is no way to communicate rotational direction that preserves the absolute direction without some shared reference. Because CP-violation is actually the only detectable way to discern between right handedness and left handedness. That is, without CPv, we would have no way to know that we aren't in a hypothetical mirror universe with all rotations reversed. Every other physical interaction behaves identically left or right. So we have a few options to deal with our rotationally-challenged alien friends: 1. Hope they can parse far down enough into the dictionary to understand what CP is and either know it or can test it. 2. Communicate using a shared reference, like pointing out two quasars that rotate relative to each other. (Quasars are pretty good galactic reference points.) 3. As long as it doesn't affect giving directions, just don't worry about it, the physics works out the same. If we ever meet and they try to shake our left hand, well, they get their very own "oops I guess electrons are negative then" situation. "And that, kids, is why you always negate earth-radians before using them in a formula." |