>>16739070
Next, we replace our background with a different background detail: namely, the Earth, which is moving at 67,000 mph around the sun, which is going at 514,000 mph through the galaxy, which is moving at 1.3 million mph relative to the cosmic background radiation. But, relative to the cube, the Earth is stationary. So what makes it different from our previous background detail? What makes the Earth anything but another arbitrary reference point to measure the cube's motion against?
Nothing.
You can see that the relative motion remains unchanged. You've been seeing the same thing every time, which is exactly the one thing we know portals to do from the games, and logically the only thing they can do. We don't even have to add background detail to the blue side because it doesn't matter: either the cube moves against the background or it doesn't, but the one thing it necessarily does is move relative to the portal. So, for the cube to be stationary in one frame of reference, the blue portal can't be.