Watch this video which may just melt your brain, and note the 3D controls on the top left, which you can use to rotate the camera around in a very cool way (especially if you're wearing a VR rig):

Created by mathematician and longtime VR pioneer Henry "Seifert" Segerman, I keep watching and trying to describe what's going on in plain English, and came up with this: Henry has installed code which simulates a Mobius transformation in a special 360 degree spherical camera to create a single infinite time loop. I think that's about right, but let me let Henry himself explain. [Update, 3:55pm: Not exactly, see Henry's clarification below.]

"Just like in the ancient video game Asteroids, when you fly off the side of the screen, you reappear on the other side, and you loop around. In the same way, the camera in the video appears to fly out the window of my apartment, reappearing in through some sort of portal floating in the middle of the apartment.

"Except the camera only appears to move. In fact, it's always sitting in the same place -- you can see the top of the tripod in the middle of the floor. The Möbius transformations let me 'zoom' the spherical images, which makes it look like the camera is moving."

To help understand how this is done, here's the original raw footage:

Henry's application emerged out of a VR project to use technology like this in live video-captured virtual reality: