Earlier today I posted about a ginormous blob of gas 80% of the way across the Universe that’s emitting polarized light, and how that’s a dead giveaway it has galaxies embedded inside it. The fact that the light was polarized helped solved a ten-year-old mystery about what’s lighting it and other cosmic blobs like it.

Now, that’s great for something that’s 100 sextillion kilometers away, but what about here on Earth? Well, it turns out polarization works down here, too. It can make rainbows disappear!

[Set the resolution to 720p or 1080p to see it best.]

Here’s how this works. First, to quote my post from this morning:

Imagine two people standing on opposite sides of a tall picket fence. There are spaces between the pickets, maybe 5 cm wide and two meters tall. One person has a sheet of plywood to hand through to the person on the other side. If they hold the plywood horizontally, it can’t get through. Duh. But if they rotate the sheet so that it’s vertical, it passes between the fence pickets easily.

Polarized sunglasses are like that picket fence. They’re coated with a very thin sheet of molecules that naturally align ...