For your entertainment, I need you to imagine this Portal situation. Consider this: you have 2 portals, as usual, and one metal rod. The rod is just long enough for its ends to meet when put into the portals perfectly orthogonal. You adhere the two ends together to make one continuous, endless rod.
Now, here's the insane stuff.
What happens if you let go of the rod? Does it accelerate downwards, move at a constant speed or not move at all?
If one of the portal's surface is relocatable and free to move, what happens if you let it fall from its original location? How does it affect the rod?
If you have a portal gun and shoot one of the portals to a different location, what should happen to the rod?
My brother doing a university course in physics (real physics, mind you) gave up. If your mind hasn't been blown, congratulations. Speculation takes place in this thread.
The portals are both set up linked vertically, right? If you jumped into the bottom one, you would keep falling indefinitely, right?
I'd assume that portals provide a connection between two points in space, and not a connection between parallel universes, thus there is still only one rod of the same mass even when it is adhered. If you take the rod and divide it up into small elements, each element is connected to the rod above it and below it. Thus to draw a free body diagram of the element, there would be gravity acting downwards and equal tensile forces acting both downward and upward. Since the tensile forces are equal, they cancel out, thus the only force acting on the element of the rod is gravity, causing it to accelerate down. Because the rod has no end (they were adhered together), all elements in the rod act the same way, thus the entire rod accelerates down at g, the acceleration due to gravity. Of course, assuming this isn't done in a vaccuum, there will be drag associated with air viscosity which will eventually limit the velocity of the rod to what we call its terminal velocity.
If one portal instantly changes places to a point farther away, we end up with a complete rod of the original length. There is still an adhesion somewhere along its length, but when one portal was switched, it severed the connection between the two ends currently intersecting the portals, giving the bar back its ends.
Thus if the portal was moving in small increments, we would observe a bunch of chopped slices of the rod. If it was moving smoothly and continuously, we would see a fine dust of shavings of the rod.
*Slow Claps*
Well done sir.
This is child's play compared to the problem sets and research I do on a weekly basis.
If the pole was falling completely normal to the ground, would it have air resistance?
Since the pole is continuous, there wouldn't be air resistance against its bottom...
Does air resistance work against the sides too?
If the portal on the bottom was moved then the link would instantly be broken portals can be moved as a pair but not relative to each other. so moving the portal and breaking the link would cause the bar to be returned to the same length it was
Now to complicate things. Lets say you have two portals set perpendicular to each other in a corner you insure a rod into the exact center of the portal and the rod is just log enough so that half way into the portal the ends meet in a corner. this corner is fuzzed together. list all the ways the bar can move.
I believe so. This is called the laminar boundary layer and it is a topic of much debate.
Quote from: Aqua on September 14, 2011, 11:16:33 pm
If the pole was falling completely normal to the ground, would it have air resistance?
Since the pole is continuous, there wouldn't be air resistance against its bottom...
Does air resistance work against the sides too?
Yes, because of the friction between the rod and the air. It's not as big as direct air resistance, but it's there.
Quote from: Ryex on September 14, 2011, 11:39:12 pm
If the portal on the bottom was moved then the link would instantly be broken portals can be moved as a pair but not relative to each other. so moving the portal and breaking the link would cause the bar to be returned to the same length it was
Now to complicate things. Lets say you have two portals set perpendicular to each other in a corner you insure a rod into the exact center of the portal and the rod is just log enough so that half way into the portal the ends meet in a corner. this corner is fuzzed together. list all the ways the bar can move.
this depends on the orientation of the portals. for example, for one configuration of portals, the bar ends may move to the left, but rotate one of the portals 180 degrees and they may move to the right. or rotate 90 degrees and they may move up or down. If they are of different orientations, a moment could also be applied because the two ends would not be moving in the same direction, causing the bar to rotate.
oh god, I just realized how bad the spelling in that post was. in any case, winkio is once again a physics master. I intended that portals were set vertically in a corner like you would do to see yourself in the games. but winkio went above an beyond.
winkio, of course, is right on the money. The first two problems are simple enough; for the first one it would simply continue to fall and accelerate until it reached its terminal velocity, at which point it would cease to accelerate and just fall. The second one is the easiest, of course, the portal link would be broken. But forgetting that moving one portal's surface not relative to the other breaks the link, reconsider the problem.
The third problem is easily the most confusing. Ryex had the right idea, but it would only work in extremely considered conditions.
I've decided to give a little insight on the third problem. Consider the portals as wormholes that act around an event horizon and a naked singularity. If you don't understand, I envy you.
Now, when the connection between the entrances of a wormhole are disrupted in any way, anything between the entrances is systematically sliced in twain exactly upon the point of entering and leaving the wormhole. Good?
Thus, when a portal is shot anywhere, the connection between the two is disturbed, the rod is sliced in two and (here's the fun bit) falls through the portal, and simply lands on the ground below the new portal's resting position due to, you know, gravity.
If anyone has problems understanding this, or disputes my reasoning, feel free to give me your mind.