I think the classic answer to the “Ozma Problem” (how to communicate to far-away aliens what earthlings mean by right and left) is the Wu experiment. Electromagnetism and the strong nuclear force aren’t handed, but the weak nuclear force is handed. Left-handed electrons participate in weak nuclear force interactions but right-handed electrons are invisible to weak interactions[1].
I think the classic answer to the “Ozma Problem” (how to communicate to far-away aliens what earthlings mean by right and left) is the Wu experiment. Electromagnetism and the strong nuclear force aren’t handed, but the weak nuclear force is handed. Left-handed electrons participate in weak nuclear force interactions but right-handed electrons are invisible to weak interactions[1].
(amateur, others can correct me)
Like electrons, right-handed neutrinos are also invisible to weak interactions. Unlike electrons, neutrinos are also invisible to the other forces*[2]. So the standard model basically predicts there should invisible particles wizzing around everywhere that we have no way to detect or confirm exist at all.
Besides gravity