/sci/ - Science & Math

An object can change its momentum by going through a portal.
If yes: Go to >>4093431
If no: Go to #2

Two portals can have different momentums as long as one side is travelling faster than the other.
If yes: Go to >>4093436
If no: Go to #3

As long as you are going one direction through the portals, the orange portal and the blue portal can be referred to as the “entrance” and the “exit” respectively.
If yes: Go to >>4093437
If no: Go to #4

The blue portal and the orange portal can still be treated as separate objects.
If yes: Go to >>4093440
If no: Go to #5

Entanglement has nothing to do with portals. It is completely irrelevant to the topic at hand.
If yes: Go to >>4093441
If no: Go to #6

I can still introduce additional views or perspectives of the model that the OP has not considered.
If yes: Go to >>4093445
If no: Go to #6

Never Click a Link: The Game.

Portals can’t move in the first place. This entire discussion is pointless.
If yes: Go to >>4093447
If no: Go to #8

OP does not have every single argument planned out in advance, and he is a massive faggot for thinking otherwise.
If yes: Go to >>4093453
If no: Go to #9

Final statement:
As described in the OP’s pic, is A the more appropriate answer, or is B the more appropriate answer?
If A: Congratulations. You won!
If B: Please read the very last word of all previous “wrong answers” I have provided you, and you will receive a special message.

>False: Portals are explicitly stated to not affect momentum. “Speedy thing goes in. Speedy thing goes out.” Its inertial status does not change whatsoever by merely going through a portal. All changes are the result of outside forces. If you messed up this early, then there’s something wrong with you.

>Implying an object's speed completely determines its momentum.
Shoot both portals on the same flat wall. Choose an inertial reference frame in which the portals are stationary. Shoot an object into portal 1 such that it travels perpendicularly to the wall: its momentum is reversed after exiting portal 2. Hence the portals have changed its momentum.

You put all this effort in just to troll a bit, don't you?
It's obviously B, any idiot would get that.

>False: Momentum is strictly a property of matter. Both velocity AND mass must be accounted for, so no matter how much faster a portal is moving relative to another portal, their momentum remains constant: 0. On top of this, portals are Entangled, so even if they did have mass, their momentums are the same regardless. There’s no new momentum added to the block, because there’s no momentum to get.

> Implying massless objects cannot have momentum.
Also, how do you know whether or not portals are made of matter?

It's B.
/thread

Also, I'm just gonna let this thread moderate itself from this point forward. There's nothing left to say, so here's a picture of a cat instead.

nither happens..if a door comes flying at you do you suddenly gain its momentum?
NO
Now if the square was on a platform that was moving towards it..yes it gains the momentum.
QUESTION ANSWERED EVERYONE GO HOME.

Are we seriously still discussing Portal physics? Seriously?

>The blue portal and the orange portal are the same 2D object. Saying one portal is different is akin to saying “The heads side of the coin is flipping, but the tails side isn’t”.
That should have given you the hint that if an object enters one Portal at a given speed, it has to exit the other at the same identical speed.

>>4093525
Dude .... first of all ... you have too much time on your hands.

The box has mass... has a momentum(is moving)
Its momentum changes as the direction of travel changes.
Protals DO NOT conserve momentum...
First understand that and leave entanglement for later!

>>4093525
>In classical mechanics, linear momentum or translational momentum (pl. momenta; SI unit kg·m/s, or, equivalently, N·s) is the product of the mass and velocity of an object (\mathbf{p} = m\mathbf{v}). Like velocity, linear momentum is a vector quantity, possessing a direction as well as a magnitude.
>product of MASS and VELOCITY
And the most retarded post of the year award goes to...

THIS GUY!

>>4093541
The direction of travel never changes if you view the box as having 20 m/s. It's motion is always linear from its perspective. However, this momentum stops the moment the portal stops, as that is what it's momentum is in respect to. Meaning, once the portal has hit the pedestal, the box stops moving.

Further more, the box has no velocity or momentum in the first place when viewed from the perspective of the portals. Again, the box either goes through the portal at 0 m/s, or it goes through the portal at 20 m/s. It does not do both.

You can't save the "entanglement" issue for later. This has absolutely everything to do with entanglement in the first place.

Jesus christ niggers. draw a free body diagram!

The portal is one object, but each side can travel at a different velocity. The momentum of the cube is sustained in relation to the "other side" of the portal, assuming the portals maintain their velocity. Unless it is subjected to other forces, like gravity.

>>4093607
But if the portal stops moving the object will still keep its original momentum, unlike what this guy thinks for some reason
>>4093592

>>4093607
>>4093608
Do you, or do you not understand what Entanglement is?

Because this entire thought experiment revolves around it. Please answer me that, at least.

>>4093621
Are you saying anything that passes through a portal becomes entangled with it?

>>4093572
>using classical mechanics to talk about massless objects
http://en.wikipedia.org/wiki/Momentum#Momentum_in_relativistic_mechanics
And you have just proven that you know nothing of what you're talking about.

>>4093526
The cube has no momentum or velocity.
The portals velocity has no effect on how the object will pop out the other side.

>>4093628
No. I am telling you that portals are not 3D objects. Even relativistic mechanics do not apply to it. That's what makes them portals in the first place.

Maybe I'm over simplifying things, but reducing the case to one that is intuitively analogous and actually verifiable seems to suggest OP is correct.
Please, correct me if I'm wrong. (Though I don't think I need to ask.)

>>4093642
Both sides of the hula hoop are travelling at the same velocity, you can't use that as an example.

>>4093626
More or less. The portal is entangled with itself. The block is entangled with itself.

It's more like the block from "before entering" and the block from "after entering" are entangled. So in respect to the portal, the block momentum of the block must remain consistent, both before and after entering the portal.

>>4093638
> Identification of spacetime points
> Not considering relativity

FBD. wtf kind of retards do you need to be, to not be able to draw this.

>>4093644
See >>4093440
It's only natural that both hulahoops have the same velocity, because both "sides" of the hula hoop are entangled.

>>4093657
So you're saying that on the original problem, both sides of the portal have the same velocity?
If the second portal was travelling backwards at the same rate the first one is moving forwards, THEN the cube would fall straight down due to gravity.

>>4093651
Hey, whatever man. If it makes you feel better to think you know what you're talking about and I'm don't, be my guest.

But I'll give you a hint: You are getting 2 different concepts confused, and you're trying to apply relativity to an object who's entire existence is an affront to relativity in the first place. Portals are entangled, and even if you could attribute momentum to them, it does not make a difference: both exist in the same momentum regardless.

>>4093642
That hoop seems relevant. Though I'd say take two hula hoops one orange, one blue. Tie them together drop it. That's essentially what's happening. Except in the game you can untie the hula hoops and when you go through one hoop you enter the other as if they were tied even though they aren't.
Though the unintuitive part comes from the fact that in doing this you create movement with no additional momentum from the moving object.
Imagine if you will you that you place a wood plank over the blue portal in your picture. Despite the block not moving as it goes through the blue portal the plank is lifted, thus a force has been applied to plank and thus there is acceleration and an increase in velocity, but the box has no change in momentum despite it changing position and changing the momentum of another object.

OP thinks too simply, assuming that there is only 2 states either side of the portal with a null set for when the cube travels through the portal.

The time in which the cube travels through the portal is critical.

Assuming the portal to be 2 dimensional and no interaction between the natural state of space either side of the portal then B is the case.

Explained in short: At the point of travel through the portal where the orange portal contacts the pedestal the cube must be traveling at the speed of the orange portal normal to the blue portal as the cubes mass is entirely on the blue side of the portal

>>4093669
So you're taking objects that cannot exist given a set of rules, then trying to support your arguments using those same rules?

See:
>>4093537

>>4093665
Not quite.

Think of 2 boxes which are entangled: One box which is viewed by the orange portal, one that is viewed by the blue portal. As the blue portal is moving, the box it views appears to be moving with respect to it. But the box with respect to the orange portal is not moving at all.

One box is moving. The other box is not. However, they are still the same box, and they still have the same momentum. The momentum only changes based on the perspective you are viewing from, but the box itself never changes.

In the same respect, the box views the portals in the same way. They are the same portal, however, one portal appears to be moving, but the other appears to be standing still. In the end, though, they are the same portal.

Does that help?

>>4093680
http://www.nature.com/news/entangled-diamonds-vibrate-together-1.9532

This is not just portal physics. These are actual ideas based on observations in nature. Portals merely present it in a bizarre way, turning the "concept" of entanglement into an "object" which you can interact with. If you're upset with me breaking relativity, then take your beef with the scientists who observed it happen.

>>4093477
I'm not even good at maths or physics, and I know the answer is A.

>>4093652
>static reactionary force, how does it work?

>>4093683
I understand, but each "side" of the portal can be travelling through space at a different rate. Space bending into the 4th dimension can creating a 2 dimensional portal, much like how in a 2D universe, space could bend into the 3rd dimension to create a 1 dimensional portal. But the 2 areas of space could bend to cause different parts of space to be touching. Imagine folding over a sheet and rubbing it against itself. You could be touching the same area on one sheet while sliding the second one over it, creating the illusion of the portal "moving" through space.

>>4093690
The normal force is only equal to that of gravity. When the pull of gravity changes, that is what causes the box to slide. Because the normal force from the before pushes it slightly to the right.

Im pretty sure your momentum into a portal is conserved coming out the other side. This is high school mechanics

Its B

>>4093652
Problem is this breaks standard physics.

>First law: The velocity of a body remains constant unless the body is acted upon by an external force.

>It is well known that the first derivative of position (symbol x) with respect to time is velocity (symbol v) and the second is acceleration (symbol a).

So... the object is changing position but has no initial velocity? Did you cover that in physics class?
If we worked backwards calculating it's position from velocity and force after it slides down etc... the box couldn't have possibly come from below the ramp and yet it did.

What would happen if the orange portal stopped when the cube was only partially through (say halfway for example)? Would it be lifted off the ground?

>>4093696
I didnt know they taught portals in high school

>>4093695
hes wrong but u dont appear to know why.

Simply velocity is relative

>>4093696
The cube doesn't have momentum. It's resting on a platform. Gravity is acting on it. Nothing else.

As soon as the top of the box appears in the exit portal (at an angle) it is under the effect of gravity in a different direction. This is the only force that is applied to the cube. The air particles around the cube do not move either. They are transfered through the portal (wormhole, etc).

TL;DR the box 'appears' out of the exit portal fast, but is not moving relative to any point around the blue or orange portal, except with a slight pull of gravity.

>>4093692
I never disagreed with that. If anything, I'm glad you understand that perspective in the first place.

Think about it: The portals are the bend in space. Space bends at the rate which the portals "separate" from each other, meaning that the portals are not changing the momentum of the block. The are just "bending" it into a different location at a quicker rate. As long as the orange portal stops moving, The rate at which the bend in space "changes" becomes zero, and the block stops changing it's "position".

Meaning that as the orange pedestal collides with the pedestal, the block comes to a complete stop as well because space is not "bending" anymore. It's momentum was an illusion of that bend in the first place.

>>4093698
Nah, it would just sit there half-way through he portal, and just start sliding downwards like in the OP from the slight change in gravity.

>>4093704
Its not at rest relative to the portal on the orange side, why would it be at rest relative to the portal on the blue side?

>>4093705
Hmmm, I didn't think of it like that before. So the question is whether or not the cube continues to be affected by the "bend" of space. Why is the only the cube affected by this bend though? Wouldn't other objects suddenly start moving once space stopped bending, since they need to maintain their momentum?

I actually like this thread and OP is right about everything except entanglement. Entanglement has nothing to do with portals, and has nothing to do with the rest of your argument either.

Prove me wrong. Go ahead prove why the spin properties of the box in question has jack fuck all to do with the rest of it.

tl;dr portals aren't real.

Portal physics sort of stop working when you have moving portals. If you have two portals with rope inbetween and you stretch the rope with the portals what force is actually stretching the rope?

>>4093710
When 10% of the cube is sticking out of the orange portal, 90% of it is still at rest at outside the blue portal, and is still under the effects of normal gravity - 10%, which will pull it to the side slightly. This will increase and eventually make the cube tumble/slide down the orange portal.

Get a portal mod and make this experiment.

When 2 portals are static, throw an object in one, and the result is obvious. Not when it is the portal that moves. Much like the the ship warping in Homeworld 2.

Say you threw a baseball straight up, and a portal on a wall moves into the path of the baseball. Would the baseball just stop moving once it moves through the portal, or would it stay in the same spot from the point of an observer. For example say someone is looking into the orange portal from the left side, if A happened it would look to him like the ball suddenly started moving towards him.

>>4093732
>comparing source engine physics to real life

What if we get rid of gravity, and just say the cube is inert relative to the blue portal until interaction with the orange. Seems like A to me.

>>4093734


>>4093738
Pretty confident it would do the same thing. When cubes tumble through portals, they are acted on with gravity in their relative directions.

>>4093744
So it moves through the blue portal and stops for no reason?
Please provide an explanation.

>>4093750
What happened when it went through the portal?
Where did that motion go?
It just stopped moving on that axis for no reason?

>>4093732
I dont think the source engine accounts for relativity

>>4093754
The ball was never moving through the X axis, only the Y axis. The blue portal made the ball appear out of the orange portal at the same speed (until it was entirely though). There's a slight spin on the ball. The orange side ball should have a very slight angle, and thus a very small X axis momentum.

Also, they don't exist, and the ones in the game require solid surfaces.

>>4093744
The cube is never moving, the portals around it are moving instead. OP assumes the portals are one thing, so if the orange portal "eats" up the block, it will lose some momentum to the blue portal which will "spit out" the block (but not give it any momentum) and go in the opposite direction with momentum equal to the one lost by the orange portal.

>>4093768
You say the ball "appears" out of the portal. This would require the molecules to be moving.

ITT: people still don't understand momentum

>>4093776
The orange portal is just a reverse side of the blue portal. If you put them back-to-back and threw a ball through one, you'd have trouble seeing their effects. As the blue portal encompasses the ball/cube It passes through the back of it (the orange portal).

>>4093787
I've been over this. If they were back to back both sides have the same velocity. In my situation the portals do not have the same velocity.

>portals can be treated as two separate objects
lolno

>>4093791
I don't even know what you're talking about.

If the orange portal is ALSO moving, then that's different. But not much.

>>4093787
>implying the portals in the OP have the same reference frame
oh you

>>4093807
>I don't even know what you're talking about.
Exactly

>>4093803
I'm done explaining, gonna go fap on /e/
Seeya later /sci/

Hello everyone, I have a couple of points to make.
1- if I put a plank across portal blue, it would be pushed off when the cube moved.
2- the cube is made of atoms, which can be visualized as mutiple layers of atoms, each one atom thick stacked on each other. the first layer passes through, then is pushed by the next, and so on, this results in the cube gaining momentum.
3- the portals are flawed, very much so, a basic flaw is that a real portal would be open on both sides, and these portals do not at fucking all act like Onestone-Rose mountain bridges, which are 3 dimensional

Portal makes no sense.

Why don't gravitational field lines go through portals? They should.

Why are people even debating this?

What happens when you throw a ball through a door?

What happens when you throw a door at a ball?

>>4093823
If gravity was effected by portals wouldn't the earth pull the distance to the portals closed if they were vertically aligned because earths mass/gravity is pulling on each side? Couldn't you float if you jumped in between just right since because earth would be pulling at you from both directions.

>>4093833
The balls crashes through the door and now you have to clean up that splintery mess.

>What happens when you throw a door at a ball?
You piss of the house owner. So stop stealing my doors you little rat bastard.

>objects moving relative to themselves
Not reading the thread, sorry. Why do you guys still talk about this. I don't think this question even makes sense without inventing some kind of hyperdimensional definition of momentum.

>>4093848
Right.

That way you'd not be able to make one of those perpetual motion machines. You'd not be able to fall "forever" like you can now.

Which is why the physics of portal is stupid. It should account for potential energy and force lines.

By the logic of answer B if I throw a life preserver over someone they should fly into the air.

>>4093833
Well people arguing to the contrary would say that in the portal scenario both sides of the "door" do not move at the same speed and in yours they do.

>>4093877
How does that have any bearing on the problem?

WHAT FORCE IS ACTING ON THE BLOCK?

>>4093877
B clearly looks retarded. It implies that the cube is flying upwards in A, when clearly it isn't.

people know that in the game of the wall the portal is in the portal immediately closes, right?

eople know that in the game of the wall the portal is in MOVES the portal immediately closes, right?

The senaryo can't happen.

>>4093926
There is a single instance of moving portals in Portal 2, which is why these threads keep going.

>>4093928
Actually, I take that back. There were two.

>>4093910
I'm not entirely sure what you are saying but you would agree with "A" in the original pic but not in the "A" in the gif is that correct?

>>4093910
It is when the reference frame changes as the cube passes through the portal.

Reference frames really aren't that difficult to understand.
So I don't get it why so many people DON'T understand them and think that A is realistic.

>>4093724
"Spin" is the inherent momentum of a particle, regardless of whether it is "moving" or not.

Quantum entanglement states that when 2 objects are entangled, their momentum changes based on the particle you are measuring. Quite literally, this is the exact same process the box is going through as you view it from the perspective of the blue portal, and from the perspective of the orange portal. The inherent momentum(spin) of the boxes remains the same from
both sides of the portal: However, the portal you are "viewing from" changes the momentum(spin) of the box. The only thing that has actually changed is that momentum is now newtonian property rather than a quantum property.


As I have said before, entanglement has everything to do with this problem. Don't underestimate me.

But the system in question is in direct contradiction of conservation of energy. It's impossible for such portals to exist due to the potential energy of falling objects. Infact, it's more likely that moving one portal would infact move the other portal.

>>4093928
>>4093941
These threads keep going because entanglement is a real property, not a fictional one. Portals are quantum physics exploded and applied to a newtonian level.

The difference, though, is that Newtonian physics and Quantum physics are the same form of physics, viewed from entirely different perspectives. One being a macroscopic perspective, the other being a quantum perspective. The serious difference is that quantum physics normally ignores gravitational forces and relies heavily on probability, so the ideas presented don't translate well into newtonian physics.

The concept of portals does NOT come from Portal. It's been around for a long time, and simply goes by many different names and with slight modifications. Regardless of what the producers of the game say, it is not ridiculous for portals to move. It simply makes the differences between Newtonian and Quantum physics and their approach just that much more apparent.

>>4093728
>If you have two portals with rope inbetween and you stretch the rope with the portals what force is actually stretching the rope?
The forces of you stretching the rope is forced stretching the rope.

Whatever the tenacity of the rope is, that is exactly equal to how much force you need to apply to move the portals apart.

>>4093722
In a sense, yes. In another sense, no. It depends on which portal you look through. If you ever looked through a moving portal, it would look as though the entire universe itself was moving. Which is essentially what happens. Changing the momentum of a portal is, in essence, the same as changing the momentum of the universe itself.

Long story short, it's just like the boxes.

When you create the portals, either there is One portal and 2 universes, or there is One universe and 2 portals. And both of these view points are entirely correct.

>>4094108
Another thing I want to throw out there is that contrary to what most people would think, even Acceleration is relative. You just need the appropriate perspective.

Say there is a ball, floating somewhere in space. Suddenly, the ball unexpectedly and drastically accelerates in a random direction. The ball becomes distorted and elongated as a result.

There's 2 perspectives you can take: Some particle the ball is accelerating in the universe, or the universe is accelerating around that particle. If you pretend that every single other particle were to move at once, but that the attractive forces in the ball allowed it to only stretch and not escape entirely, you've just created a view in which infinite energy was applied to the system, but an infinite amount of energy minus the attractive forces withing the ball was applied in the opposite direction.

This means that each of these perspectives can contain the same momentum, despite their drastically different views. Now I know one of the biggest objections people will have is that I subtracted from infinity.

But frankly having closed system with no momentum suddenly gain massive velocity was just absurd in the first place. Whether you are subtracting from infinity, or if you are adding to zero, neither of these concepts actually work in real life unless we pretend they do (when we do that, we call them "closed systems").

Honestly, this is the biggest reason I think people struggle with higher math and quantum physics: They take everything that was once intuitive to us and shows how absurd it actually is.

>>4094061
Oh yeah, I just remembered: The really funny part about the momentum of the box?

It just so happens that each perspective is the "negative" of the other. The box viewed from the "blue" portal will have a negative "spin" of the box viewed from the "orange" portal. Is that shit crazy, or what?

I wish I could only describe how warm and fuzzy inside that makes me feel.

I should probably point out that you cannot place portals on moving surfaces. Apart from that one part in Portal 2 with Wheatley fruitlessly trying to hack a computer, but that bit was weird.

>>4094309
The portals we are describing are not the same portals from the game Portal. They are very similar, however, these portals are able to move. Using examples from the game doesn't really solve our problem unfortunately...

>>4093752
It's kinda been explained this whole thread.

See >>4093705