>>16739065

First, consider this basic, stripped down scenario with just two portals and a cube in a blank void. Quick: what, if anything, is stationary and what is moving? Trick question; you can't answer that of course. Not only is it an impossible question, it's literally *nonsensical*. The word "stationary" has literally no meaning within this featureless white void. All we can observe is that there is *relative* motion between the cube and portals.
Note, also, that this motion is symmetrical: every part of the cube that goes in the orange portal has to appear on the blue side. This is, in fact, the only logical outcome: there is nowhere else for it to go. You may recognise this principle of symmetry as expressed in the game itself, "speedy thing goes in = speedy thing goes out".
Notice something else? Without any frame of reference given, this relative motion is just what we'd expect from portals. It's identical to what happens in the games.