Portal [Interesting Physics]

[darkshark]

Re: Portal [Interesting Physics]

If one were to very slowly position themselves to the midway point through both portals on the ground, do you float?

[Reincarnate]

Re: Portal [Interesting Physics]

In the game, you bob back and forth forever

[darkshark]

Re: Portal [Interesting Physics]

Worlds shortest particle (or hell pretty much any object) accelerator.



Red = Magnets

Or remove blue portal once the object is up to speed to create a ridiculously powerful railgun of sorts.

[_Stepdude_]

Re: Portal [Interesting Physics]

In the game, you bob back and forth forever

I guess it's because the momentum you have when you enter the portal never ends. If you put anything through the portal with x speed, it will exit with x speed and then fall back through the portal with the same speed as before. Even if gravity pulls it down through one portal, the exact same thing happens with the other portal, so they cancel eachother out. Creating the only variable to be the momentum.


I'm sorry, I'm really tired so I hope I made any sense >_>



EDIT


Though if an object were to be placed smack in the middle of 2 portals on the ground, I don't see why the object wouldn't stop.

[qqwref]

Re: Portal [Interesting Physics]

If one were to very slowly position themselves to the midway point through both portals on the ground, do you float?

I imagine you would. If you just put something in one of these portals, it would oscillate back and forth, but eventually air friction should bring it to an effective stop.

It's a bit hard to imagine a gravitational field that completely switches directions on a line, but it's probably easier to imagine an electric field with the same behavior (at least thinking theoretically). A point charge in that field would show the same behavior.

[Van T]

Re: Portal [Interesting Physics]

Say two spaceships fly off in opposite directions at speeds greater than .5c
The net speed between the two would be greater than c, so would each observe the other as going backwards in time?
e: For the sake of ease of communication/mingling, there are portals linking the two ships

[Ickalanda]

Re: Portal [Interesting Physics]

2. The second one doesn't work. If you were able to put the portal on the table then that means that the table is larger than the portal, meaning it wouldn't fit through another portal since they are all the same size in the game.

This is retarded. You're talking about portals, why limit them to the properties of the video game? Clearly if portals could exist, they would be able to be different sizes.

How is this retarded? If a portal is opened connecting two places in space, both the entrance and exit must be the same size unless they are modifying the spacing of the particles entering them, and either way this prevents the table deal from working.

As can be seen in the posted image, the table traveling through the portal will quickly be halted because the size of the table is determined by the portal on it (I am assuming the portal can not go beyond the edges of the table.

This means that the physical limitations of the table quickly halts any sort of exponential growth you might expect to occur from this situation, as I said in my original post. The table will collide with the other table (or itself o_0) much too quickly into the process, halting movement.

The only way to get this to work is to mess around with the sizing of the portals, making it make even less physical sense than the portals already do haha.

[~kitty~]

Re: Portal [Interesting Physics]

Wouldn't sound be able to travel through the portal?

EDIT: I would imagine portals being very very dangerous in real life. What would happen if a portal disappeared while you were going through it?

[leonid]

Re: Portal [Interesting Physics]

you will be cut in half

[qqwref]

Re: Portal [Interesting Physics]

Related: http://www.webcomicsnation.com/thors...&chapter=26170
(That frog thing is a living portal.)

[Reincarnate]

Re: Portal [Interesting Physics]

I imagine you would. If you just put something in one of these portals, it would oscillate back and forth, but eventually air friction should bring it to an effective stop.

It's a bit hard to imagine a gravitational field that completely switches directions on a line, but it's probably easier to imagine an electric field with the same behavior (at least thinking theoretically). A point charge in that field would show the same behavior.

Well the idea is that the momentum you have going through one portal is conserved, so you've basically got a velocity vector always pointing towards the ceiling and being pulled back down to earth, hence the oscillation (and, ideally, slowdown to a halt due to air friction).

However, it makes me wonder how forces work here since you're still feeling a downward force of gravity through the portal even though it's pointing up at the ceiling (meaning that the attraction between the earth and your body is somehow directly extending beyond the portal itself).

[qqwref]

Re: Portal [Interesting Physics]

Good point about gravity. It probably makes sense for gravity to extend beyond a portal; if we use the "2D rubber sheet" model the portal is a tiny cut in the sheet, and the area "behind" the portal is still affected properly, but if you think of gravity as relying on line-of-sight stuff, this breach in space would make the gravitational field beyond the portal really questionable. I wonder: if we put one portal on the ceiling, would someone be pulled towards the opposite portal? From the perspective of someone near the opposite portal, there is basically another earth beyond it, and it ought to provide its own gravitational attraction. The game seems to act like only matter and light can go through the portal (but not fields of fundamental forces), which is pretty odd from a physics standpoint.

I guess Portal physics is like a very tall cup with a hole at the bottom. If you look deep enough, you find that it doesn't hold water....

[LongGone]

Re: Portal [Interesting Physics]

However, it makes me wonder how forces work here since you're still feeling a downward force of gravity through the portal even though it's pointing up at the ceiling (meaning that the attraction between the earth and your body is somehow directly extending beyond the portal itself).

You probably just have a system where the object is divided into two by the portals (two lumps of group of atoms). Well, I think of portals as physical boundaries; forces/gravity does not extend past it, it just treats the portal as a solid barrier. Each half will independently experience gravity, however they are both linked by the portal so they exert a force of each half's own weight against each other. Equilibrium is reached when the plane of the portal cuts the centre of mass of the object; i.e. the total gravity force exerted by each half on each other is equal. If you displace the object slightly, the side with more mass will exert a slightly larger force (its weight) on the other side with less mass, thus oscillate

EDIT: On second thought, maybe forces do transmit through each other till a certain extent; since if you had a pole through a portal and you yank at it it pulls through (the atoms of the pole are all linked together by forces afterall). Maybe gravity does pull through to a certain extent? Or overlaps slightly on each other right on the portal

[Stewie7Griffin]

Re: Portal [Interesting Physics]

Two portal faces couldn't be pushed together with an object in between as the object would be pushing out of the other portal against itself, completely preventing you from pushing the portals together. Unless you can somehow defy the laws of physics by getting the object to ignore the it's own boundaries and go inside itself BEFORE you push the portals together, those portals are not going to go together.

[Izzy]

Re: Portal [Interesting Physics]

The portal has no physical properties. It is completely flat and can be described as only 2 dimensional. Having two portals push together would apply the same force the object in-between as if those portals weren't there. Except the left side is now pushing from the right and the right is pushing from the left.