Time is something we don't even have a bad definition for. Let alone a rigorous scientific definition.
Crystals In Time by Frank Wilczek, Scientific American, November 2019, p. 28.
- Crystals are orderly states of matter in which the arrangements of atoms take on repeating patterns. In the language of physics, they are said to have “spontaneously broken spatial symmetry.”
- Time crystals, a newer concept, are states of matter whose patterns repeat at set intervals of time rather than space. They are systems in which time symmetry is spontaneously broken.
- In physics Space Symmetry holds the Laws of Physics apply everywhere equally. Time Symmetry holds the Laws of Physics apply at any time equally. Time Symmetry is denoted by \(\tau\).
So what is time symmetry?
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