/sci/ - Science & Math

[Anonymous No.5968808]

[Anonymous No.5968817]

Only morons who don't understand relativistic physics will answer A.

[Anonymous No.5968824]

>>5968808

now back to /b/

>inb4 samefagging both sides of an argument just to self-bump

[Anonymous No.5968825]

B of course.

[Anonymous No.5968827]

>>5968808
You can't even place a portal there in the first place..

[Anonymous No.5968833]

>>5968827
you can in Portal 2 was level where portals were on moving platforms

[Anonymous No.5968836]

Can't say which.

The device violates our laws of physics to begin with, so trying to use our laws of physics to answer the question is pointless.

[Anonymous No.5968835]

This is the 928207474 time we have this discussion.

[Anonymous No.5968837]

>>5968824
>This result does not follow the conservation of energy
Then it's wrong. There is absolutely no difference between moving a cube through portals and moving a cube through a hula-hoop, except the location of the space on either side of the portal/hula-hoop. While the space above and below a hula-hoop are continuous and local, and the space on one side of a portal is disconnected and apart from the space on the other side, this disconnect makes no difference in the transfer from one space to another through a gap in an object.

[Anonymous No.5968841]

>>5968837
>>>/b/

You are not wanted here.

[Anonymous No.5968843]

>>5968824
>Portals don't follow conxervation of energy

[Anonymous No.5968845]

>>5968835
Momentum is a vector. Neither situation conserves momentum.

[Anonymous No.5968846]

>>5968837
>>This result does not follow the conservation of energy
>Then it's wrong.
Maybe if you had finished reading that sentence you would have learned that this isn't something uncommon with portals.

[Anonymous No.5968858]

A.
I made the map in Portal 2.

[Anonymous No.5968866]

>>5968845
Then that means that portals can give energy to objects.
Which isn't that hard to believe, since changing the location of an object can also be seen has providing work to it.

[Anonymous No.5968863]

>>5968841
If you had a brain you'd realize there is nothing wrong with what I said. B is true, nothing I wrote contradicts this.

>>5968846
It is inherently wrong to think portals contradict any law of the conservation of energy, was my point. There is nothing to contradict in a form that is a loop that has a different area of space behind it than the one in front of it, like even a hula-hoop.

Even for passing a cube through a hula-hoop it must exit one side at the same rate it enters the other. So what?

[Anonymous No.5968868]

>>5968843
>samefag

[Anonymous No.5968875]

>>5968863
>So what?
So the cube received energy from merely passing through the portal.
Once it passed through, there is no reason for it to suddenly stop moving.

[Anonymous No.5968927]

Now first of all, there is no right answer because the portals themselves violate some very basic laws.
Which one you deem correct is only dictated by how you look at portals and from what perspective do you look at them. From my perspective pieced together by looking at the forces at work here the solution is A. Let me elaborate:
The cube sits still on top of the table feeling the force of gravity pulling down on it and the table resisting. Now as the portal moves over it, which to the cube seems like a door frame would move over it, the only thing that changes from the cubes perspective is the angle of the force of gravity, and since the friction can not combat it it slides down. There is no force that would suddenly make it accelerate.
The cube feels the same effect as you would if you sat on a table which suddenly tilts for 45 degrees.

[Anonymous No.5968930]

Portal is a 2007 first-person puzzle-platform video game developed by Valve Corporation. The game was released in a bundle package called The Orange Box for Microsoft Windows and Xbox 360 on October 9, 2007[5][6] and for the PlayStation 3 on December 11, 2007.[7] The Windows version of the game is available for download separately through Valve's content delivery system Steam[1] and was released as a standalone retail product on April 9, 2008.[4] A standalone version called Portal: Still Alive was released on the Xbox Live Arcade service on October 22, 2008; this version includes an additional 14 puzzles. A Mac OS X version was released as part of the Mac-compatible Steam platform on May 12, 2010.[8]
The game primarily comprises a series of puzzles that must be solved by teleporting the player's character and simple objects using "the Aperture Science Handheld Portal Device", a device that can create inter-spatial portals between two flat planes. The player-character, Chell, is challenged by an artificial intelligence named GLaDOS (Genetic Lifeform and Disk Operating System) to complete each puzzle in the Aperture Science Enrichment Center using the portal gun with the promise of receiving cake when all the puzzles are completed. The game's unique physics allows momentum to be retained through portals, requiring creative use of portals to maneuver through the test chambers. This gameplay element is based on a similar concept from the game Narbacular Drop; many of the team members from the DigiPen Institute of Technology who worked on Narbacular Drop were hired by Valve for the creation of Portal.

[Anonymous No.5968935]

>>5968863
>It is inherently wrong to think portals contradict any law of the conservation of energy, was my point.

Well your point was wrong. Put the exit portal higher up than the entrance. Boom, conservation of energy violated. It's not that complicated.

[Anonymous No.5968937]

>>5968927
see
>>5968824

[Anonymous No.5968938]

>>5968937
As I said, there is no right answer. From my perspective this image does not change a thing.

[Anonymous No.5968944]

>>5968927
You should neglect gravity. Assume there is no pedestal and no gravity, just a stationary cube and a portal rushing toward it.

>Now first of all, there is no right answer because the portals themselves violate some very basic laws.

There may not be a right answer, but we can identify wrong answers. An answer must be wrong if it leads to a contradiction. The two options given are really proxies for two theories. Let the velocities before and after be v1 and v2 and the velocities of the portals be v_o and v_b (orange and blue). All velocities are measured in the lab frame, and directions for each vector are measured relative to the corresponding portal (positive velocity is the direction into orange and out of blue).

Theory A: v2 = v1
Theory B: v2-vb=v1-vo

Theory A leads to a contradiction in the case vb = 0, vo<v1<0. In this case, the box and the orange portal are moving down, but the portal is moving faster. Given the setup, the box must enter the orange portal. Theory A says that the box will exit the blue portal with negative velocity, meaning that it cannot exit the blue portal. So the box enters the orange portal but cannot exit the blue. A contradiction.

Theory B does not say this. The relative velocity of the box coming out of the blue portal will be positive under this theory whenever v1>vo, which is exactly the case in which the box enters the orange portal.

Because Theory A gives a contradiction while B does not, only B can be true. (Though it may not be; there could be a third theory. But none has been proposed.)

[Anonymous No.5968950]

>>5968944
Both contradict some pretty basic laws. If you look from the tables perspective the cube suddenly accelerates, which also contradicts all logic. Portals are immobile in the game because of this paradox. I stand my ground on the point that there is no answer to this puzzle because portals themselves are paradoxal.

[Anonymous No.5968953]

>>5968944
samefag from >>5968950
Your maths stand from the frame of reference of the orange portal but not from the frame of reference of the rest of the world. The clash of those frames of reference are the paradox here.

[Anonymous No.5968964]

>>5968950
I don't mean that they do or don't violate laws of physics. I mean, specifically, that Theory A is internally inconsistent. It says that things that go in one portal don't come out the other. Theory B is perfectly consistent.

In fact, I believe it is possible to work out a version of Theory B that really does work, in concert with at least Newtonian mechanics. This will involve the portals doing work on objects that pass through them, applying forces on those objects, and creating and destroying matter, but that's OK. For all we know, a real object *could* do all those things, but no real object could make something exit a portal and also *not* exit that portal.

[Anonymous No.5968970]

>>5968953
No, all measurements are in the lab frame (ignore the rotations necessary; consider this as a theory when the orange portal faces down and the blue portal faces up). Because theory B uses only relative velocities, it is the same in all reference frames.

[Anonymous No.5968973]

>>5968964
Okay you might be starting to convince me here. Good job. I am usually hard to be moved in my opinions.

[Anonymous No.5968979]

>>5968944
>All velocities are measured in the lab frame
I'm not a physicist, but is a frame of reference even meaningful for a space that is not simply connected?

The points of view of the two portals are at least locally simply connected. The viewpoint of the lab is not, in any way.

[Anonymous No.5969000]

>>5968979
We needn't assume anything about the connectedness of the space. We can just assume that it's a normal Euclidean space, but there are portals that, when a particle goes in one, it disappears and an identical particle comes out the other.

[Anonymous No.5969030]

The problem is that there isn't anything to make the cube move...

If you think about it at an atomic level, the portals are basically 2 dimensional, and since they're moving, over time they advance past a layer of atoms. Suddenly those atoms appear at the other portal, but that's it. The moving portal keeps moving, and the next layer of atoms appear at the other portal, but nothing has moved the first layer of atoms at all. Which means all that happens is the cube exits the other portal in a 2 dimensional form.

[Anonymous No.5969038]

>>5969030
>i'm still in elementary school

[Anonymous No.5969049]

>>5968938
>From my perspective this image does not change a thing.

Then you didn't read it. The answer is B.

[Anonymous No.5969053]

>>5969038

Take a planck slice being teleported, what makes it move afterwards?

[Anonymous No.5969062]

>>5969053
Any particle that goes in one portal is accelerated as it passes through so that delta-v_in = delta-v_out. For stationary portals, this simplifies to the well-established rule v_in = v_out.

[Anonymous No.5969061]

>>5969053
The other plank slice being forced inside the portal.
So basically, itself being thrust.

[Anonymous No.5969066]

>>5969053
the law of conservation of momentum

[Anonymous No.5969080]

>>5969066
>>5969062
>>5969061
>citing physics laws in a situation that obviously doesn't follow the laws of physics overall

This is all under the assumption that there's no interface discontinuity here

[Anonymous No.5969089]

>>5969080

[Anonymous No.5969098]

>>5969080
>This is all under the assumption that there's no interface discontinuity here
What do you mean by that?

>citing physics laws in a situation that obviously doesn't follow the laws of physics overall
I (>>5969062) didn't cite any laws of physics; I just gave a rule. Incidentally, that rule is the only one that works, since other rules lead to contradictions (see >>5968944).

[Anonymous No.5969103]

>oh look, this thread again
>open thread
>ctrl-f "hula"
>6 minutes in

goddamnit, /sci/, can't you pleasantly surprise me ONCE?

[Anonymous No.5969108]

>>5969103
>ctrl-f "hula"
Lost my shit.