Science reduces the question What is light? to what it does but the mystery remains that what it does isn’t physically possible. Even after centuries of study, physics still can’t say why:
1. Light doesn’t fade. Every physical wave diminishes in amplitude over time but light doesn’t, even after it has traveled for billions of years.
2. Light has a constant speed. The speed of a wave depends on the medium it travels through but light goes at a constant speed in space that is physically nothing.
3. Light is a wave and a particle. It is physically impossible for a wave to act like a particle or for a particle to act like a wave but light is a wavicle that denies this.
4. Light always finds the fastest path. It isn’t possible for a physical particle to find the fastest path to every possible destination but light does.
5. Light chooses its path after it arrives. A physical particle can’t pick the path it takes to a given destination after it arrives but light does just that.
6. Light can reveal an object it doesn’t physically touch. In a purely physical world, it shouldn’t be possible to detect an object without touching it but light does exactly that.
7. Light vibrates outside space. Light vibrates into a dimension that doesn’t physically exist.
Most physicists think light is physical yet physical reality can’t explain what it does. The paradox that physical light acts in non-physical ways is exemplified by wave-particle duality, that light is like a wave sometimes and sometimes like a particle. A wave traveling in a medium doesn’t arrive like a particle at a point, but light does. A particle going in one direction can’t go in many directions at once like a wave, but light does. No physical wave ever becomes a particle and no physical particle becomes a wave, but light seems to exist as a mixture of both.