Here's another link to the same animation:
https://gfycat.com/likelyfaithfulabalon ... ppy-aww-ok
In addition to each ball moving in a straight line, there's another interesting mathematical relationship in there.
A pair of balls on opposite sides correlate to sin and cos, where the two balls travel orthogonally to each other (that's 90 degrees to normal folks). When one ball is at the center (0,0) the opposite ball is at the max, either (1,0) or (-1,0), and vice versa, thus if one ball represents the sine, then the other ball is the cosine, or vice versa, depending on which side of the railroad tracks you were born.
As demonstrated by this animation:
Of course all that is already obvious to anyone familiar with the theory behind the Fourier Transform. I am, of course, referring to Euler's Formula.
Fourier Transform:
And then substitute Euler's Formula:
Easy Peasy.
