The Portal Dilemma: The Case Of The Teleporting Cube

“PLOP” or “WHOOSH”?

The Portal Dilemma — Illustration created by the author

Imagine a world where portals exist. You could enter a portal from one location and come out of another portal in another location. Throw in a few science fiction elements to this imaginative setting, and you find yourself playing “Portal”, a simulated physics-based puzzle video game.

Portal, the video game, features a “portal gun”, which fires an entrance portal onto a surface on the first fire and an exit portal onto another surface on the second fire. The game requires the player to use this tool to navigate complex spatial platforming and problem-solving puzzles.

I have fond memories of playing this game as a teenager. Recently, I came across an interesting portal-based discussion. The setting of this discussion is as follows:

There is an entrance portal on the face of a moving piston that leads to an exit portal on the face of an inclined surface at, let us say, 60° to the floor. Now, as the piston moves fast downward, it moves toward a flat platform. On this platform, there is a cube (object).

You could imagine that as the piston moves downward with the entrance portal on its surface, the cube gets teleported out of the exit portal on the inclined surface. Given this setting, the question is if the cube comes out…