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Suppose we are in communication with aliens who live in a different universe. I know, that's impossible, communication requires the exchange of mass or energy, which implies that we live in the same universe. But suppose it is true. I am wondering, can we and the aliens, via this communication alone, ever come to an agreement on what constitutes a "right handed rotation thru a 30 degree angle"?. I sit here and imagine a vector pointing upwards thru the center of my mouse. Using the right hand rule, I rotate the mouse +30 degrees about that axis. Is there any way, talking to the alien without exchanging any mass or energy, that I can get the alien to do the same?
We can't use beta decay, because they might be living in what we would call an antimatter universe.
I mean, if we could exchange photons, I could send the alien what I call a right-handed photon, spinning right-handedly about a vector axis pointing in the direction of propagation and say "this is what I call a right-handed rotation" and then we could come to an understanding. I might do the same with a massive particle, but if the alien lives in what I call an anti-matter universe, there would be an explosion, the alien could report this, and then I would have to send a massive antimatter particle. Or tell them to use beta decay.
But without a shared physical example, I don't see how it can be done using communication alone. Have I missed something?
We can't use beta decay, because they might be living in what we would call an antimatter universe.
I mean, if we could exchange photons, I could send the alien what I call a right-handed photon, spinning right-handedly about a vector axis pointing in the direction of propagation and say "this is what I call a right-handed rotation" and then we could come to an understanding. I might do the same with a massive particle, but if the alien lives in what I call an anti-matter universe, there would be an explosion, the alien could report this, and then I would have to send a massive antimatter particle. Or tell them to use beta decay.
But without a shared physical example, I don't see how it can be done using communication alone. Have I missed something?
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