Alright - walk me through why it would lose speed going through a floor-ceiling portal system. If I kneel down next to the floor portal and peer down, I’m going to see a room below me with me looking through a portal, etc. It’s essentially a bottomless pit.
See my post above. Are we talking about the world of the game? Or a world where something like portals exist but energy is somehow conserved? If the former, you’re right: the object would fall indefinitely, constantly gaining speed. This is because the gravitational force is constantly doing work on it; it’s always moving in the direction of the force, which means that the gravitational force will always be doing positive work on it, and it’s a general statement that any object that has positive work done on it will see its kinetic energy increase.
If, on the other hand, we demand that energy be conserved, then it must be, somehow, that any positive work done by gravity at some point in the cycle must be balanced out by a corresponding negative amount of work later in the cycle. In other words, the object must, at some point in the cycle, experience a force that opposes its motion (this is the definition of negative work.) Thus, the gravitational forces must rejigger themselves in such a way that they slow the object down for part of the cycle, but speed it up in other parts.
But what would these forces actually look like, you ask? I honestly don’t know. It’s probably possible to solve Poisson’s equation in a space which has two portals in it, but you’d need to make them behave slightly differently in the game (if you approach the “floor” portal from below, you’d need to be able to come out the “ceiling” portal moving upwards as well, but this never happens in the game, so it’s unclear how well it matches onto the game’s mechanics.)
Simple way to put it: Gravity, like any conservative force, can be expressed as the gradient of a potential. High points are at higher gravitational potential than low points, and so to go from a low location to a high location, no matter how you do it, you have to be moving against the gravitational field at some point.
Fundamentally, portals like the ones in the game are impossible for the same reason that Escher’s continually-ascending staircase are impossible.
Sure you can - if the energy cost of maintaining the open portal includes it.
Fair enough. There’s no evidence of this in the game, of course, but maybe a star winks out somewhere in the cosmos every time you pass through a portal.
In some of the promotional material, there’s mention that the gun itself is powered by a small black hole inside of it (which could indeed be used to produce a prodigious amount of energy). It’s unclear whether energy is transferred from the gun to the portals every time something passes through, though. I suppose that wouldn’t be any more implausible than anything else in the game.
I was talking to someone in another board about this, found this topic here, and I spent a while thinking about the different interactions you’d get, so I figured what the heck, I’ll see how it goes as a first post here. Hullo folks! Pardon the text diagrams.
Again, if you arranged portals like so:
[Downward facing]
—Falling
—object
[Upward facing]
How is gravity supposed to propagate through the upward facing portal from the ground?
There would be a very complex gravitational field:
–[downward portal]
- ///-\||||//-\ \
---------/||
--------Object
---------||/
/-//–//||\ \ --\-
–[ upward portal ]
There would be a flux from the mass of the object interacting with itself, as well as the partially obstructed interaction from the planet which would induce lateral acceleration towards the outer edge of the bottom portal, additionally there would be acceleration towards the inner edge of the bottom portal due to the gravitational field being warped as it passes up and in past the bottom portal and up through the top portal.
In space there would only be the self-interaction with it’s own mass from the top and bottom (well, front and rear as there is no up or down in space) portal which would be very interesting as the pull from the rear portal would peak as you were about to cross the front portal, briefly vanish as you passed through and counteracted the effect, then the pull from the front portal would be peaking just after you crossed through, and weaken as the effect from the rear portal grew.
Essentially when you were directly in between the two portals you would be an equal distance from two objects massing the same as you do for a three body interaction, and when you were passing through the portals it would resolve into a two body interaction which would then transition back to the equidistant three body state as you neared the midpoint again.
–O--[-O–]--O–
—O-[–O-]—O-
----O[—O]----O
-
- -([)—(])- - -
O----[O—]O----
-O—[-O–]-O—
- -([)—(])- - -
It wouldn’t just be a three-body interaction: You’d also get interactions from more distant copies of the object. It’s similar in some ways to having two parallel mirrors, where you get an infinite number of images and images of images and images of images of images, etc.
Nothing so dramatic. It’s actually powered by a nigh-infinite array of really small potato batteries.
Yeah, but those would be overwhelmed by the lateral tug around the edges for most objects unless you had a black hole between them.
Indeed, though the array immediately collapsed into a black hole, but hey, potato… event horizon, what’s the difference?