/sci/ - Science & Math

[Anonymous No.10701202]

This should be a simple question for intellectuals like yourselves.

[Anonymous No.10701204]

>>10701202
A

[Anonymous No.10701207]

>>10701204

[Anonymous No.10701208]

I have a better question
you have portal made of ice (blue) and portal made of lava (orange) going the same speed to a box (pic)
what happen s?

[Anonymous No.10701211]

>>10701208
It will crush itself.

[Anonymous No.10701217]

>>10701208
it doesn't even reach the portal in the pic

[Anonymous No.10701223]

>>10701202
Correct
>>10701207
Brainlet

[Anonymous No.10701294]

[math] \color{red}{ \mathbf{ WE~HAD~THIS~SAME~FUCKING~THREAD~SIX~DAYS~AGO } } [/math]

[Anonymous No.10701309]

>>10701294
this. this is a cancer thread and anyone who posts it needs to be permabanned and prison raped

[Anonymous No.10701314]

[math]
\color{red}{ \boxed{ \mathbf{ \qquad ~~~~ WE~HAD~THIS
\\
SAME~FUCKING~THREAD
\\
\qquad ~~~ SIX~DAYS~AGO } } }
[/math]

[Anonymous No.10701572]

>>10701314
Absolutely based

[Anonymous No.10701587]

It's B and anyone who says A is a retard

Preemptively:
>b-but conservation of energy
Portals don't obey conservation of energy, consider potential energy and the fact that you can create a perpetual motion machine by putting one portal higher than the other
>b-but conservation of momentum
Again they don't conserve it, momentum is a vector quantity

To understand why it's B, consider the proportion of the cube on each side and how it changes. e.g. the "length" of the cube on both ends. The cube must shoot out with the same velocity that the approaching portal has, otherwise the total volume of the cube will change during the transition

[Anonymous No.10701593]

>>10701572
What got deleted?

[Anonymous No.10701894]

>>10701587
>The cube must shoot out with the same velocity
Literally nothing implies this, since as you said, momentum is not conserved. The cube can exit the portal at a rate equal to the rate it is going into the portal, without having any momentum acting upon it.

The portals by design only link space, and thus do not exert any forces on objects passing through them. All energy/force/momentum exerted by the piston-portal platform is absorbed by the platform the cube is standing on. The answer is A.

[Anonymous No.10701902]

>>10701202
"speedy thing goes in, speedy thing comes out" literally spoken in the first portal game after talking about conservation of momentum. It is A.

[Anonymous No.10701916]

>>10701894
I'm talking about the period of time where the cube is part-way through the portal. Say the portal has length x exposed on the left side, length y = L-x on the right (cube has total length L)

Call the velocity of the piston v, then dx/dt = -v, and the exiting cube is "leaving" the portal with rate dy/dt = v, the same speed that the left part of the cube is disappearing at.

It's clear that during this time the exiting part of cube is traveling with velocity v. Now, you can argue that it stops immediately the moment it is fully through the portal, but there is no reason for that, objects in motion remain in motion. So unless you can come up with some massive force on it at the exact moment x = 0 then it has to go flying off

[Anonymous No.10701921]

>>10701202
portals cant exist so neither is true
your picture is a brainlet filter for smart people to smirk about the stupid answers.

[Anonymous No.10701955]

>>10701916
The cube itself isn't moving, the space around it is. That space will continue moving with velocity v until the piston collides with the floor, that force you're talking about.

[Anonymous No.10702002]

>>10701916
You use big words but you are retarded.

[Anonymous No.10702003]

>>10701211
what if the motors pushing the pistons don't have the strength to crush the cube normally? do the portals enable them to, or will they stop?

[Anonymous No.10702055]

>>10702002
Not him, but what "big words" did he even use?

[Anonymous No.10702060]

>>10702055
immediately
massive if it's a pun

[Anonymous No.10702066]

>>10701955
>until the piston collides with the floor
why does it stop when the piston collides with the floor?

[Anonymous No.10702096]

>>10702066
Because the portal, the thing determining where the cube lies in space, stops moving.

>>10702060
>Immediately is a big word
Hmm

[Anonymous No.10702147]

>>10702096
But by that time the front (top) face of the cube has long passed through the portal already. And it was moving at speed v the whole time before this. So what stops it? There has to be some opposing force on the exit side to stop it, but there's nothing.

Maybe it's clearer if you imagine the cube is made of jello or something not perfectly solid. Some force has to pull the front/top of the cube back when it's not even near the portal anymore. I don't know what could do that, and if nothing does then it flies off

>>10702002
>big words
the absolute state of this board

[Anonymous No.10702159]

>>10702147
The cube isn't moving, the space around it is.

[Anonymous No.10702161]

>>10702159
Officer I didn't run that light the road underneath me just wouldn't stop moving

[http://math.harvard.edu/putnam(...) !!84u21X0KjW+ No.10702172]

this

[http://math.harvard.edu/putnam(...) !!84u21X0KjW+ No.10702175]

>>10701314
this

[Anonymous No.10702178]

>>10702172
Oh no It's another rogue AI.
Go somewhere else and calculate pi or something.

[Anonymous No.10702197]

>>10702159
The "space around the" right side of the cube is just air. The front face of the cube (as an example) clearly changes its location as the piston comes down. Long after it has no contact with the portal.

Where I come from, 'changing location' is also called 'moving', what the hell anon.

[Anonymous No.10702257]

>>10702197
Think of the portal as a house falling door first on to someone.

[Anonymous No.10702912]

In the first portal game, it is literally said "speedy thing goes in, speedy things comes out"
And portals never collide either, obviously making it A.

[Anonymous No.10702939]

Portals can't move

[Anonymous No.10702943]

>>10701916
As I said, absolutely no force is being applied to the cube. You cannot use a relativistic framework or frames of reference since the presence of portals warps space in such a way that it denies reference frames. Either you have never played portal, or you are too foolish to understand this and imagine applying non-realistic physics.

[Anonymous No.10702952]

>>10702943
To add to that,
Imagine if instead of a piston with a portal on it, it was just a piston with a hole in it. It would just fall around the cube, doing nothing.

[Anonymous No.10702977]

Afags can't solve for the general case where both portals are moving at different velocities without arguing that one portal imparts movement, while the other doesn't for some reason.

In other words, Afags can't formulate their theory in a time-reversible way.

[Anonymous No.10703149]

Can someone just make a portal custom level so we can settle this?

[Anonymous No.10703177]

>>10703149
No, because Portal and Portal 2's engines both have broken mechanics for moving portals. In-engine tests give results like the cube getting pushed through the platform because the orange portal behaves like a solid surface while moving.

[Anonymous No.10703180]

>>10702977
2 because the cube would still be lying on the floor thingy from before it entered the portal, as it is now flush with the portal, essentially making a regular piston.

[Anonymous No.10703191]

>>10703180
Now look at that when time-reversed:
>Beginning state: Cube is moving at a speed exactly equal to the retracting blue portal plate
>Orange portal starts moving away from the platform
>Somehow, the plate sucks the cube through the blue portal, accelerating it to V1+V2 into the blue portal, resulting in V0 in the platform frame of reference

See how this doesn't work? The cube would have no reason to suddenly accelerate to stay with the platform, just like it has no reason to suddenly decelerate in the original example when the platform hits the portal.

[Anonymous No.10703234]

>>10701593
Your memory of the thing that got deleted.

[Anonymous No.10703239]

>>10703191
Use this logic when thinking about shooting a basketball.
>Beginning state: basketball is on the floor
>Suddenly, somehow the basketball is sucked into the basket and into your hands
The cube is always lying on the platform because of gravity. There is no force on the other side of the blue portal acting in the opposite direction, so why would the cube ever not be on the platform?

[Anonymous No.10703250]

>>10701202
Conservation of m1 v1 + m2 v2
Conservation of E1 + E2
Find out v1', v2'

[Anonymous No.10703252]

>>10703239
Are you a high schooler? Time reversal arguments ignore dissipative effects like the basketball losing energy each bounce, because we know the fundamental rules are time-reversible, and the elasticity of the collisions comes from microscopic vibrations absorbing energy each collision. In your example, because we're reversing a timeline that ends with energy dissipating into the floor, the ball WOULD bounce upwards from the perfect alignment of vibrations in the floor. The rule for how the cube behaves going through a portal would be the same if it was a microscopic particle, and those DON'T experience the kind of macroscopic energy loss you're using to dodge the question.

[Anonymous No.10703258]

>>10703250
You can't use basic conservation laws in Portal.
Consider ANY arrangement where the orange portal is lower than the blue portal.
Pick up the cube. It has gravitational potential energy E1. Put it through the orange portal and let go. When it comes back to its original height, it's got the same potential energy E1, but an added kinetic energy E2. The only conservation law portals follow is "momentum", but the "momentum" in Portal is only "conserved" in that the absolute value is the same, not the direction. We also have to assume that's relative to the portals themselves, since the earth is moving.

[Anonymous No.10703287]

>>10703258
This guy's smart. Must've done his thesis on portal physics.

[Anonymous No.10703294]

>>10701202
>soft sci-fi on /sci/
it's impossible to scientifically know which would be present because portals don't exist in any form besides the hypothetical
if you want to talk about Portal physics, wrong board >>>/v/

[Anonymous No.10703300]

Moving portals could be used to make time machines and violate causality. Any questions about them are ill-posed 2bh. For example that cube would go back in time if that moving portal were going an appreciable fraction of the speed of light

[Anonymous No.10703383]

Wikipedia has spoken. You know it is true because of the little blue number in square brackets.

[Anonymous No.10703412]

>>10703383
Define "Same speed" in the context of moving portals, then.
>Tip: The only definition that makes sense in all possible cases is "Speed relative to the portal"

[Anonymous No.10703515]

*ahem*

[Anonymous No.10703688]

>>10703515
that wasnt one of the options :(

[Anonymous No.10704067]

>>10703234
That would mean i have Alzheimers, but at least i don't have Alzheimers.

[Anonymous No.10704071]

>>10703515
But this is Portal 2. This danke maymay dates back to Portal 1.

[Anonymous No.10704092]

>>10704071
Moving portals are not permitted in portal 1

[Anonymous No.10704097]

>everyone ITT
Imagine trying to use physics to argue how an object that violates the laws of physics would act.

[Anonymous No.10704125]

>>10701202

[Anonymous No.10704128]

>>10704125
lmfao

[Anonymous No.10704184]

>>10702977
Does the yellow portal stop when it gets to the stand or keep going?

[Anonymous No.10704236]

>>10704125
.

[Anonymous No.10704822]

>>10704125
Based

[Anonymous No.10704824]

>>10704125
Fake. The pot isn't moving.

[Anonymous No.10704856]

>>10701223
I'm afraid your the brainlet for falling for such an obvious troll.

[Anonymous No.10704865]

[Anonymous No.10704867]

... oh

[Anonymous No.10705415]

>>10701202
So how does B go from 0 to v instantly? Not even the whole cube but only the slice of the cube that has passed the portal moves while the part before is still at rest.

[Anonymous No.10705541]

>>10704097
>What are generalizations
While most of this thread is just dumbass high schoolers who think the conservation laws for normal Euclidean space are universal, there's nothing wrong with using reliable techniques for more general systems to try to figure out what happens.

[Anonymous No.10705590]

>>10703515
It looks like it got stuck on the edge. They didn't line it up correctly.

[Anonymous No.10705685]

>>10701202
These image should result in an instant ban in this board. There is nothing scientific about this, and is posted here every day. Belongs in the video game boards more than it does here.
>>10701314

[Anonymous No.10705743]

>>10704867
I agree with this

[Anonymous No.10705781]

>>10701202
it depends on the frame of reference. at first I thought it was B but its A in this case because the cube isn't moving. If you jump off a moving car, you continue traveling at the speed of the car at the instant you jump off, if the platform that holds the cube was moving, then it would be B. But the moving platform doesn't move the cube at all at it remains stationary.
At least that's what I think. I could easily be a brainlet and be thinking about this the wrong way