Light.
A word so simple it couldn't be simpler.
A phenomenon so common it couldn't be more common.
Yet it's a thread running through the entire history of human science, a mysterious fog that remains elusive well into the 22nd century.
When people mention light, what pops into most people's minds these days is probably wave-particle duality.
Then comes Ultraman Tiga, followed by the terms interference and diffraction.
Actually, though.
Human contemplation of the nature of light goes all the way back to BC.
For example, in the ancient East.
People believed the sun was a manifestation of deities—like Xi He, Sun Lord, East Lord, and the Golden Crow shot down by Hou Yi and so on.
As for the ancient West, at first Empedocles' views were most popular.
He thought the world was made of four elements: water, fire, air, earth. And that the human eye was ignited by the goddess Aphrodite using fire, with light belonging to fire.
