Comment on Which is it Lemmy?
mirshafie@europe.pub 1 day ago
B.
Momentum/velocity is not an intrinsic property of an object, it is a relative property between two objects in a frame of reference.
Behind the yellow portal is the part of the universe where the blue portal is. The yellow portal, and therefore the space where the blue portal is, has momentum relative to the cube.
Put yourself in the frame of reference of the cube. You see the yellow portal come toward you. Imagine there are objects on the other side of that portal. You see those objects rush toward you through the portal. Why would the objects just stop dead when you came through the portal? (If they did just stop, it would be as though you hit a wall, and you wouldn’t actually go through the portal at all.)
kryptonianCodeMonkey@lemmy.world 1 day ago
Also consider the duration of the time that the portal is passing over the cube. It is moving at speed, the entire way through the portal and out the other side and then it just stops dead immediately once through? That would hardly be a conservation of momentum anyway from any frame of reference and does not make any intuitive sense.
mirshafie@europe.pub 21 hours ago
This exactly. Consider an object that isn’t a point mass (like the cube) going through. As the first atoms go through, and thry just stopped relative to the portal boundary, that would suggest the next layer of atoms need to exert force on the first layer to push through. But portals in the game Portal do not have any resistance to objects passing through them.