>>718464201
Now, we're going to make the cube "stationary". How? By adding a little background detail on the orange side, in the form of a friendly astronaut floating in the void, moving along with the cube. The cube can therefore be said to be stationary within the astronaut's frame of reference. But what does this actually mean for the cube? As you can see, the relative motion between the cube and the portals remains exactly the same. The astronaut merely being there does not change at all what happens here. Speedy thing goes in, speedy thing goes out.
I won't belabour the point by illustrating it but we could furthermore add more background details that move with the orange portal, or don't move with anything, and then we could say that the portal is stationary, or once again nothing is - depending on what you measure it against. The astronaut and cube could both be moving relative to something else. "Stationary", as you can see, is just a relative measurement that exists in relation to something else. It is not a property of the cube itself, and it does not change the fact that there is motion between the cube and the portal.
You should be able to see where this is going.
