Circular polarization is something I’ve always wondered about but never knew was real. If electromagnetic waves have amplitude in one direction, why not two? or three? After all, there are compression waves, too.
So I would think, some nights when I couldn’t sleep: if a wave moving along the axis Z had a wavelength W along the perpendicularY axis, and a similar wavelength along the doubly perpendicular X axis, wouldn’t it propagate in a helical fashion? And if you change the phase, won’t it change the handedness of the helix? As it turns out, yes it does. I only just found out it’s an established phenomenon (as I might have guessed) while researching stereoscopic methods for a post.
Of course, it doesn’t have to be circular. The more general form is elliptical polarization, but that doesn’t look as cool.