/sci/ - Science & Math

Here is my theory. At first I felt somewhat strong in it, but now I'm starting to doubt myself. I'm not sure if the movement through the portals would generate velocity and an instant acceleration for the cube as I formerly thought. I would appreciate some input.

First law of physics in the Portal universe: portals cannot have motion relative to each other.

The portals are like one solid object in spacetime. Every new Portal creates a new unmorphable object.

>>7899965
https://www.youtube.com/watch?v=mCQiwhik8nc

The cube has no momentum. Where does its momentum come from in scenario B?

Isn't this like HS Physics?

>>7899869
You can't solve this question with real life physics. It's pretty easy to see this. Consider the standard way to build up speed in the portal universe (two portals one directly above the other, separated by some hight [math] h [/math]). Start at [math] h [/math] and then fall into one portal, you'll convert your potential energy [math] E_{p} [/math] into kinetic energy [math] E_{k} [/math], but there's a problem here you'll continue to increase your velocity until you reach terminal velocity, but where has the extra energy come from? We started with some [math] E_{p} [/math] and ended with [math] E_{k}' [/math] which is much greater than the energy we started with. We've violated conservation of energy, now there are three options here:
>There's some non-trivial spacetime here which uses physics magic to allow all this to happen with out violating any conservation law.
>Portals can't work IRL (most likely) making this question pointless.
>There's some hidden action at work here conserving energy (and momentum for that matter)

>>7899876
Here you seem to have picked a particular rest frame to do all your calculations in, that isn't Galilean invariant.

>>7899869

Every time this is posted we fight about it, and every time B wins.

>>7899869
>>7899876

B is the correct answer, but your reasoning is not correct. Your problem is the same as most A-fags, in that you're not properly dealing with frames of reference.

There is no force applied to the block, ever (except for gravity), and the block never accelerates. It is ALREADY moving at high speed RELATIVE to the portal, and so it doesn't NEED to accelerate. This is easy to see if you imagine the view looking INTO the blue portal: you see a piston with a block approaching you at high speed. The block continues passing through at high speed (hence B) and the piston slams to a halt because it can't fit through the portal.

If you didn't know the orange portal was moving, it would be extremely straightforward. And it IS extremely straightforward, because it doesn't matter if the portal is moving or the block is, because all motion is relative anyway.

>>7900068
>>7900039
>>7900032
Thanks guys, I appreciate it. I know it's a fictitious trifle, but this kind of puts my mind at ease.

>>7899869
The solution is that "portals" as depicted in the image cannot exist. If they did, you could create the situation in this image. An object could fall forever, accelerating forever, generating infinite energy, violating thermodynamics.

So, since this kind of portal cannot exist in our universe, you can choose whichever option in OP's image you like, because they're both equally impossible.

>>7900079
>the situation in this image
aaaaaaaaaaaaaaand here is the image

>>7900079
>you can choose whichever option in OP's image you like, because they're both equally impossible.

It's called a thought experiment you stupid faggot. Nobody here thinks portals are real.

>>7900104
>It's called a thought experiment
No, it isn't. It's called science fiction and there's a difference between science fiction that might exist, some day, and science fiction that we can prove to be impossible within the laws of physics in this universe. This one is the latter, kid.

>>7900117

No, it's called a though experiment, kid. Virtually every thought experiment is not physically possible (e.g. frictionless surfaces, etc.). "but dat can't real" is just a cop out for dumdums.

>>7900068
You're wrong. The block has no energy. It doesn't continue passing through at high speed because it was NEVER moving at all, you fucking idiot. Don't respond to me with whatever retarded thing pops into your stupid head.

>>7900262
It was stationary relative to the portal
So when the portal is moving, after passing through it retains that velocity

So the portal essentially imparts velocity onto the block through its own movement.

>>7900262

b8 post

>>7900264
And how does it do that? What force is used to accelerate the block?

Let's say you have a block of wood on a table and a tube of cardboard that can fit the block inside its rim.

No matter how fast you slam the tube on top of the block, there is no force acting upon the block, so it doesn't move.

When the portal slams down on the plate holding the block, all that happened is the block *appeared* to enter the new frame of reference quickly, but was stationary the entire time.

Because the block isn't moving, the frame of reference is.

>>7900280
>Because the block isn't moving, the frame of reference is.

I think you should do some research about what a "frame of reference" is.

>>7900264
Not you idiot. Make a circle with your hand. No encompass something with your hand. No matter whether you do that fast or slow, that thing you pit your hand aroudn isn't going anywhere because it didn't move. You're so fucking stupid oh my god Jssus please come and kill these people.

>>7900280
This 100%. Tag teamed him.

>>7900279
On a bait board. Because a lot of people in this thread >>7900288 are hella dumb and these are the philosophical leaders of the age. God damn you all.

>>7900288
Alright, awesome. Not a physicist so I just wanted to be sure my reasoning was retarded.

>>7900289
A portal is not just a circle
A portal is a portal

The cube has velocity relative to the portal, it keeps that velocity as it teleports to a different location

>>7899869

This bait pasta has been posted on /sci/ nearly every day for the past couple of years, why do people even reply to it? Are you all new or there are simply no quality discussions going on on /sci/ board so the only thing left to do is shitpost in a pasta thread that has not had an conclusive answer for years now

I wish A-fags were as creative as flat earthers. This "hurr durr but if you drop a hula hoop" stuff is just boring.

>>7900305
Have you played the games? Portals don't teleport. Portals act like circles, but with one half of the circle in one location and the other half in another location.

IDK, if someone is dedicated enough to create a simple map in Hammer, we could resolve this immediately.

Otherwise, I think the entire problem stems from the fact that people are working with inconsistent definitions of portal behavior.

>>7900321
https://www.youtube.com/watch?v=UH6p-Ab9f9Y

I'd say, B. I say this because:

>As moving objects pass through portals, they come through the exit portal at the same direction that the exit portal is facing and with the same speed with which they passed through the entrance portal.

If that's true, then the block doesn't need to have the momentum itself, it matters how fast it passes through the portal. The portal "falling" on the object, makes the object move through the portal, at the same speed the portal "fell" on it.

>>7900068
Ridiculous. This would imply that the thing holding the cube would experience some sort of deceleration force

>>7900389
>This would imply that the thing holding the cube would experience some sort of deceleration force

"Deceleration" is not a thing, but yes, it does accelerate relative to the other piston, of course. They have a high relative velocity and then they have a relative velocity of zero. Acceleration.

>>7899869
We figured this out a long ass time ago. Its A. The cube isn't moving, the portal is. I'm also pretty sure someone already tested it and put it on youtube, but i'm too lazy to check.

>>7900322
portals don't move either

Its A you are all retarded the block isn't in motion...

>>7900453
No fucking way. So this is proof that physics student are literally retarded?

The thing that has portal and is moving towards the cube never directly touches the cube with something physical as to give it momentum. So when the cube passes through the portal the cube will just slide down.

t. Pure Mathematics major.

>>7899980
It also has momentum when it's emerging form the portal. Where does that go if it just flops down?

If you have moving portals momentum isn't conserved.

>>7900395
I think you meant that the block has a high relative velocity but and absolute velocity of zero. I,e, if you were to hit it, it would do the same damage as if it hit you but really it had no energy, just inertia.

>>7900462
You're stupid.

Why did I parents train us not to call someone stupid and stop talking to them. It is literally the most liberating thing in the universe. Are parents the OG SJWs?

>>7900461
Ok, as the cube is emerging from the blue porter it is moving with respect to the blue portal. It has momentum. You suggest as soon as it is leaves the portal it will stop. You're saying it will loose that momentum despite not having any forces acting on it.

That's even worse.

The reality is that if you had moving portals momentum is no longer conserved. Hence B.

>>7900483
>it is moving with respect to the blue portal.

And why would this affect the cube at all? The cube is completely inert as it passes through the portal.

If you had a portal moving horizontally, say... to the left. As it is approaching your horizontal position you run towards it as to go through it, when you come out the other side will you somehow start magically moving to the right?

>>7900128
This. Experimental data almost always has a %error compared the theoretical calculations.

>>7900470
>the block has a high relative velocity but and absolute velocity

There is no such thing as "absolute velocity."

>>7900461
You forgot to add "freshman" before "pure mathematics major"

>>7900499
And there it is. Relativism has made it into physics. Confirmed for not joining me in the awareness of absolute reality.

There is absolute velocity. You're just too stupid to know it.

>>7900492
>And why would this affect the cube at all?
Because the part of the cube that has already emerged has momentum in the lab frame. That doesn't just disappear the second it leaves the portal.

>>7900502
Just ignore him. He is just a retarded physics major. Too lazy to go full applied engineering and too stupid to go full pure mathematics. The absolute scum of this earth.

>>7900502
>relativity has made it into physics
>general relativity and special relativity
>all reference frames are equal
>acting like this is new
What highschool are you currently attending?

>>7899869
Why dont you just download garys mod and find out for yourself

>>7900507
I can't. I don't know why. I just can't. i want to save him from being so retarded and also because its a public forum I wanna save the lurkers too who see me comment and stop being dumb. Its my responsibility.

>>7900509
That is not what relativism means. Stay in your lane, squidward. Practice that clarinet and stop blaming spongebob for the fact that you suck.

>>7900514
Someone please do this and put it on youtube so these threads can die. It's A.

>>7900514
>Why don't we just use a vidya game to simulate a relativistic problem that involves objects that violate thermodynamics?

>>7900530
The ad hominem, it burns even more than the utter lack of intelligence.

>>7900536
>Why don't we use the source engine to figure out how the situation works within that frame.
Is how someone who isn't retarded understands the question.

>>7900536
>Why don't we just use a vidya game

Because this comes from a fucking videogame you moron. Unfortunately this board is filled with a bunch of physics major smug fucks that think that if they half-assedly apply the laws of relativity they can get the 'true, true!' answer but this is not what the question is about. This is a question about your understanding of the physics OF THE GAME.

This shows that physics students are so close minded that they cannot imagine a different system of physics and much less can they make predictions about what would happen in such universes.

Don't worry, I'm not saying that you are not a real girl gamer xD so please put back on your shirt about a game you have clearly never played and most definitely feel free to keep posting in discussions about a game that you haven't fucking played.

4chan used to be good.

>>7900421
nigga, >>7899974
they do sometimes in Portal 2

>>7900558
Just don't man. Stop fighting this pointless fight. These pseudo intellectuals haven't played the game but you know what they did? They watched DNews videos or minutephysics video about relativity so now they are top tier scientists and their only duty in life is to educate us peasants.

It is not even worth the bits of data we are occupying in 4chan's database to entertain this discussion with people who are so clearly uniformed pop scientists.

>>7900545
No this is a thought experiment involving an imperfectly simulated aspect of a game implemented in real life where physics isn't the product of an imperfect code designed to be used on a commercial grade computer.
>4chan used to be good
No it didn't

>>7899869
You cant move a portal like that. The wormhole is only stable as long as you dont move it.
Even the game got this right, so I dont see how this question could come up.

>trying to make this happen in Hammer
>create setup in Portal 1 editor only to realize Portal 2 is only version that allowed moving portals on brushes

>>7900603
The physics of the game are realistic. Either way you're a stupid retard and wrong.

>>7900604
>even the game got this right
>>7899974

>>7900608
Please do this so we can stop this dumb thread and maybe put some armchair physicists on suicide watch :))

>>7900617
https://www.youtube.com/watch?v=S85nudR6D-Y

There we go. Much realistic. The engine cannot deal with it.

This is why you don't trust the video game, because what you get out is simply the prescription put in by the developers. It's not necessarily general. Just about any simulation can give unphyisical results.

This is why cilicilised folks have actually been doing the thought experiment.

>>7900654
Nah, it can. It just can't handle a completely still object going through. If you move a bit while it's coming down (even crouch) it works. I'll post a vid in a little bit.

So many people are going to be mad.

>>7900654
So the game can't give us an answer because it's not programmed to take objects in portals like that.
But too bad that doesn't answer our question on how it would act if it could. Still, interesting video.

>>7900662
Yes, that's in the video (it shows the player being propelled faster than the piston) too but you're not understanding the point. If the engine blatantly doesn't work for an object at rest then it is wrong. Just because you can get it to work doesn't mean it isn't garbage.

>>7900674
Fair point.

So, in the end, there is no answer.

\thread

>>7900676
>>7900674
Not quite. We're still discussing what would happen using IRL physics. If the portals existed it would contradict the conservation of energy and conservation of momentum, but we are still trying to figure out just what would happen.

portals disapear when moved

>>7900759
read the thread

>>7900690
Oh my god your retarded.

Neither your fucking idiots, if a surface with a portal on it moves the portal dissipates.

>>7900766
lurk more

>>7900765
>your retarded
>your

>>7900665
He was just replying to the people that think using the game is a valid test of how it would actually work.

>>7900765
Were you born this stupid or did you have to work on it?

To all the B people.

If the portal is travelling at the speed of light, how can everything that passes through travel at the speed of light?

>>7901257
dude what? Nobody's going the speed of light. Slow down, man.

>>7899869
I thought you guys were supposed to be ultra awesome math geniuses? It's simple. Create a universe where this is possible, and calculate what happens.

>>7899869


IMAGINE A CUBE ON YOUR DESK

IMAGINE THAT YOU SLAM A CARDBOARD CYLINDER (LIKE FROM A TOILET PAPER ROLL) ONTO THE CUBE

IF YOU LOOK THROUGH THE TOP OF THE CYLINDER (BLUE PORTAL) THEN THE CUBE APPEARS TO BE MOVING TOWARDS YOU

BUT, WHEN YOU HIT THE DESK, THE CUBE DOES NOT MOVE

SO, THE ANSWER IS A

>>7901295
what is with the influx of people here who do not read the thread?

>>7901329
What? Where in thread is anyone doing anything remotely to my idea?
>hurr it's a gayme it can am no work.
>It violates my mother and the laws of physics.

>>7899869
Let's assume the Portal Gun has a built-in energy source that allows it to compensate for potential energy of the earth's gravitational field.
Because of this it is not possible to argue from conservation of energy.
However, let us consider the game mechanics:

One of the most important rules of Portal is that from the point of view of someone entering a portal, direction and amount of their own velocity relative to the area around both portals does not change.
In other words, there is no jump in velocity.
You don't instantly go from 0 to 100 because it would feel very wrong to the player.
If you jump from a platform into a portal to make a horizontal jump, it looks as if you're jumping towards the area behind the portal.

Now, imagine that a Portal, and by extension the area on the other side, is moving towards you.
You can see the area behind the portal coming towards you.
Ignore everything else and just focus on the area behind the portal.
If the portal were to finally touch you and make you pass it, to make things feel right from your point of view you would have to keep moving towards the world behind the portal, i.e. scenario B.

>>7901327
>I AM AN IDIOT BUT I AM ALSO A LOUD IDIOT SO YOU SHOULD LISTEN TO ME

>>7899869
answer B
becouse thing appears from portal sequentially rather than instantly
thats why velocity will be same.
/thread

It's A. Just like many people have said, just imagine the portal is any cylender that you can pass through. You moving that cylender has no effect on the cube.

Here's a super simple way to look at it, kids:

A wall with a hole in it is moving towards you, you step over the lower part of the hole so as to avoid touching the wall. The wall doesn't affect you in any way, right?
Now imagine the hole in that wall is made by two portals alligned perfectly to make a window.

Wowzers it still doesn't affect you.

Golly gee, guys, physics is hard.

>>7901823
but the wall doesn't teleport you to a new location. The two instances are not the same. I'm not going to insult you.

>>7901826
From an outsider's view someone stepping through a portal would seemingly be teleported, but from the "teleporters" view they are just stepping through a portal (literal definition, a fucking door m80). The entrance and exit of said portal being in two very different places does not magically add momentum or actually make the person teleport.

I am going to insult you, you're retarded.

>>7899869
proves its impossible to have a moving portal, because an accelerating/decelerating portal while object passes through would stretch/shrink a solid object on the other side.

>>7901833
So, from the teleporter's view, the entire world is rushing at them (not just a wall with a hole, but everything beyond that wall as well) and then suddenly stops for no reason, and all that momentum just evaporates magically?

Makes sense.

>>7901823
>A wall with a hole in it is moving towards you

Which is the same thing as you moving towards the wall. It's B.

>>7899869
As stated in Portal, passing through a portal has no effect on momentum, thus, the answer is A.

>>7901987

You mean the answer is B.

>>7901992
Actually, I was mistaken. You're right.

It's B.

>>7901926
Except the world isn't actually moving, so you're a moron

>>7901823
>>7901833
>>7902016
I'm 90% sure you're baiting, but I gave you the benefit of a doubt and made a small sketch for you.
In the upper picture a portal is moving in positive y direction with velocity v.
In the lower direction the cube moves towards the portal with velocity v, and the second portal also moves in negative y direction with velocity v.
The upper and lower picture depict 100% the same situation, except in the lower picture the frame of reference is moving in positive y direction with velocity v.
There is no gravity or air present.

Now, apply the logic of A (the velocity of the portals is irrelevant) to my thought experiment:
In the upper frame of reference the cube would be engulfed by the first portal and remain stationary outside the second one.
In the lower picture the cube would fly into the first portal and then leave the second portal with velocity v in positive x direction.
This is a clear contradiction, therefore A cannot be physically correct.

>>7902101

Relativity is a meme theory and it does not apply to real life or video games

>>7903787
Hit the brakes in your car without the seatbelt, see what happens :^)