/sci/ - Science & Math

ey yo wagwan blud it is gonna be A as the block has no momentum and therefore cannot shoot out unless the big red thingy with the orange portal fucking slams the stand the block is on giving momentum to the block

portals aren't real

>>9885437
define how portals work
are they simply a windowframe with some "program" or supernatural pheomenon of sorts attached to them that joins two points in space?

these arguments always turn into shitshows because people go into it with different ideas about how portals work and instead ignore the portals and treat the system using their normal understanding of physics or the world while taking the mechanics of the portal for commonly granted

>>9885479
I love how you're trying to respond reasonably to a troll thread.

I'm sure this will end well

>>9885479
>are they simply a windowframe with some "program" or supernatural pheomenon of sorts attached to them that joins two points in space?
And what's the difference?

>>9885717
I listed those as examples of the first type
I never mentioned an alternative view because desu I do not understand the alternative view that usually starts by repeating some newtonian preservation of motion or something and I can only assume it is because they have a different idea how portals connect stuff

I like to think of the case where a ball is resting on top of a very tall but thin pedestal and somebody slams a hoola-hoop portal down along the pedestal (the hoop does not stop sliding down the shaft of the pedestal, so at the other end of the portal it looks like the pedestal is rising up)
Would the ball suddenly launch off the pedestal according to view B? I have no idea

>>9885723
The way I see it there's mostly one sensible option really, the things that go into a portal must come out at the same rate through the connected portal, nothing else to it.

>>9885728

The fuckery comes in because, unlike the hula hoop example you gave where both "sides" of the portal are moving the same relative to each other, the picture shows only one side of the portal moving.

>>9885437
Portal do not conserve momentum.
this situation is not physical.

anything can happen depending on the rules for your imagination.

>>9885437
We can't make any assumptions on portals since they violate physics. But assuming the portal walls don't touch the cube, what would happen if you dropped an empty portal(window)over it?
A. Nothing
B. Cube goes flying up into the air @ g
>>9885756
And this.

>>9885756
>>9885798
Portals don't change physics in any way, other than allowing stuff that goes in them come out at a different location. That's it. It's a completely plausible thought experiment.

>>9885807
that's a violation of conservation of momentum. to think about this, you'd have to construct and entirely knew (fake) physical paradigm.

>>9885807
>Portals don't change physics
>But you can use them to have an infinitely accelerating object
Seems to violate conservation of momentum desu

>>9885818
>>9885816
portals don't change physics, OTHER THAN allowing stuff to go through them. b-bu muh momentum is irrelevant, since the law of momentum becomes "objects conserve their momentum, except in the case of portals where stuff goes differently"

>>9885825
you don't know enough about physics to have this conversation.

>>9885829
I see you ran out of arguments already, but nice cop-out

>>9885831
infant confirmed

>>9885437

In a world with portals, momentum is not conserved, since space isn't homogenous anymore.

Dev who worked on the actual game said that B makes more sense than A.

>>9885825
If you disregard conservation of momentum, that changes everything you unimaginable brainlet. Gtfo.

>>9885437
Paradox since the event changes depending on the reference frame, as one case would cause the other to violate cons of momentum

>>9885855
But it doesn't change anything outside of portals. If there's no portals around, everything keeps working fine and dandy. If there is a portal, it can break conservation of energy since that's what portals do, simple as that. Explain to me the problem here, other than "but it breaks what they told me about physics in high school :("

>>9885847
this nog too tries to force existing physics on it as if portals have to use what is currently known

>>9885864
>PORTALS DON'T CHANGE PHYSICS!!!!!
>Here's how they change physics
>But it's okay because they don't change physics!!!
This is you. You are what we colloquially call in physics a "fucking retard."

>>9885437
A

>>9886007
>PORTALS DON'T CHANGE PHYSICS!
>...outside of portals
good job consistently ignoring half of what I said, brainlet

>>9885847
>"B is consistent with the frame of reference of the blue"

Blue is in the same frame as the cube. This guy has no idea of even basic physics.

So this depends on which context and laws the cube is being subjected to.

If the cube automatically becomes subjected to the post portal world, then it is B, if it remains subjected to the pre-portal world, it's neither. It will just stay put at an angle.

You can solve this with another question.

Assume that the blue portal isn't accelerating downwards. Assume instead that it just approaches the cube slowly and eventually engulfs it.

Does the cube fall, or does it stay put?

That is in essence what is being asked here. This is why it is fictional, because you are drawing up imaginary rules for this portal without knowing what rules would have to be applied to get it to work.

Friends


Imagine dropping the empty ring, no portal, on top of the cube. the cube sits there, of course obtains whatever energy from the platform shaking.

Think about it this way, when you drop the portal on the cube, it "sits there," which, in the photo, is equivalent to being placed in the air out of the portal, being subject to g, and falling. NOT flying out, as that momentum is transferred to the platform.

>>9886269
A follow-up:

the REAL question, is, IF, at time t/2, half the cube is subjected to free-fall, and the other half is on the platform, does the half on the platform tilt on its side to some angle?

Portals can move objects to higher locations, which would require some energy input. They can do this indefinitely, so we can assume there is some (nearly) inexhaustible energy source in the portal gun.

Imagine watching the portal come down on the cube frame by frame. You could watch the cube come out of the portal at the same velocity as the other portal. It wont suddenly lose all of its kinetic energy once the entire cube comes out. B.

>>9885447
It needs momentum in A if it's going to exit the portal at all. The difference is that in A, that momentum is abruptly stopped as it finishes rising out of the portal, and in B it continues on with the same momentum it was traversing the portal with.

B is the easiest to explain by far, biggest issue with it, is the sudden jump in velocity when you are in the platform's frame of reference. Causality breaks down in both examples.

>>9886306
There isn't even an issue with the sudden jump in velocity. As the platform accelerates towards the box, the box is accelerating towards the platform from the platforms frame of reference. There is never a sudden instantaneous jump if you consider what is happening before the box touches the portal.
B makes more sense now matter how you look at it.

>>9885463
>portals aren't real
this is true

their existence creates space time paradoxes and other problems that have no answer like this >>9885437

the OP may as well be asking if:
>A) is green hot
or
>>B) is a square happy

neither answer can be a true statement because the questions are gibberish.

>>9886339
The box and the platform has the same velocity before the portal, but after they suddenly have different velocitys without either of them accelerating. You can't explain that without: "its just portals bro"

>>9885864
>explain to me what the problem is other than the very glaring obvious one

>>9886171
Portals completely break causality. Trying to figure out what happens next is utterly nonsensical. Stop pretending to understand even basic physical principles, because it's clear you dont.

Lets say you have an object in free space, and that the object has nonzero dimensions. Say you have two portals, one stationary and the other in motion at speed v. If the portal in motion passes around the object, the object will pass through it, keeping its velocity relative to the portal structure constant and be seen flying out of the stationary portal at speed v. But this relies on its speed being relative to the moving portal before the event, relative to the stationary portal after the event, and so relative to both of them during the event. This works fine as long as the portal isn't accelerating, but consider what happens if the portal stops moving halfway around the object. If what matters is the object's velocity relative to the moving portal then it stops halfway out of the stationary portal. If what matters is the object's velocity relative to the moving portal then it continues moving through the stationary portal, which would be viewed as it suddenly speeding up while halfway though the portal that's just slowed down. In practice I imagine the result will be akin to the average of these situations, since half the mass will relative to each portal, but it's a nonsensical situation to consider in the first place.

>>9885437

if u can predict what happens in this you solve all portal problems

>>9886306
nah it would just slide down as the base that the block was originally on blocks the blue portal

>>9885479
This.

Last thing i remember reading from somewhere was the only possible way of teleportation/portals was disintegration then recreate you on the other side

You people don't listen do you? Speedy thing goes in, speedy thing goes out. A portal in the Portal games is LITERALLY just a hole. It does NOT affect or alter the objects that pass through it in any way.

It is A. If you have a basket ball lying still on the ground, and you drop a hoola-hoop over it from high above, it doesn't matter what speed the hoola-hoop is going at. The basket ball won't move.

>>9887067
b-but muh frames of reference that I learned about in highschool

>>9887067

>>9887067
Then how do you solve >>9886695's accelerating portal?

>>9885437
Did you make this thread just to put it off OP?

>>9887067
How does A exit the blue portal when neither of them are moving? It has to move to even get through it.

So the question is then, when it has gone all the way trough the portal; does it then instantly stop in its place on top of the portal, or does it continue on with the same speed it was moving out of the portal with?

You have to address this.

>>9887546
I think >>9886695 actually has a good conclusion here.
>In practice I imagine the result will be akin to the average of these situations

>>9886724
Picture isn't very clear, but it probably would be like 2 pulleys
rope could freely move back and forth
if pulleys come closer, rope slackens
if pulleys go farther, rope tightens

not sure why the rope comes out the backside of the portal

>>9887078
>first principles arent important because you learn about them in high school
I guess the pythagorean theorem and quadratic formula are for high schoolers only.

>>9887067
>he believes forces acting on a portal's platform affect the other portal's platform as if they were one object

>>9885437
https://imgur.com/a/IYOWC
Read this around a year ago, may be worth the read.

>>9885437
hmmm,,, it really makes u think

>>9889314
how are you such a brainlet
do the same thing except with the blue portal moving upwards

>>9889316
Who's the real brainlet here?

>>9885437
It's simple, the cube emerges at the blue portal at the speed of the yellow portal which means that every particle that comes through is moving with that same speed relative to the blue portal. You can argue portal physics and say the cube doesn't gain momentum but then it just gets smeared around the blue portal because it can't emerge without momentum.

Here is a problem for B fags. Supposedly you can change the mass of the cube but it will still fly out at g, that obviously cant happen.

C the portal closes to avoid A/B aerguments

>>9889314
thanks for making this
although I wish the pillar was either vertical or the cube was sliding sideways in A

It's B

Here's how to figure this out. Make the yellow portal big enough to fit the entire stand inside it. The only difference here is that now the whole stand will go through instead of just the cube.

With this minor change, you can see that the cube would be shooting through the blue portal because the cube is coming through with momentum. The actual end position of the cube makes no difference other than to confuse people.

Just because the cube is stationary in reference frame 1 doesn't mean that it is stationary relative to reference frame 2, which is the blue portal.

>>9887067
That's wrong though because the basket ball and the hoola hoop are in the same reference frame, whereas a portal changes reference frames once it passes through.

This is why an astronaut and his space ship can be moving really slowly in space, but from the point of view of earth they are moving thousands of miles per hour.

>>9889555
Literally has nothing to do with anything.

>>9885437
Put your shirt sleeve over your arm super fast, see what your hand does

>>9889164
tl;dr "what you see is what you get" which is basically what I just tell people now after explaining it over and over again.

It's B.

>>9885437
Portals can't be moved. Therefore, the only way for first scenario to happen is to have the rest of the scene moving, so it's clearly B

why doesn't someone just build this level in the game and see what happens?

>>9886724
Is this a Neon Genesis Evangelion reference?

>>9890891
kys

>>9890580
Because youd have to code new physics for it to work. Then obviously it'll be whatever scenario the builder chose

>>9889679
Except that the blue portal is in the same frame as the cube and the stand, so relative to the blue portal, the cube has 0 speed.

>>9891245
>so relative to the blue portal, the cube has 0 speed.
Wrong The relative speed only matters for the entry portal and that information is transferred to the exit portal. Which is why you can place portals on opposing surfaces and walk through them.

A of course. My friends and i talked about this a long time ago, but i still remember it, 'cause i made the best argument and i'm still fucking proud of myself. Place your left hand palm up, then place smth on it, it'll be out "cube", then make an OK sign with your right hand and move it down, so the "cube" goes through the ring made by index finger and thumb. This is basically OP's picture, but handmade. The left palm is the platform, the inner side of the index-thumb ring (that's one where your right palm is) is the orange portal and the outer side is the blue portal. By "simulating" the pic you can see, that "cube" doesn't fly out of the "blue portal". So again, it's A. I know that i'm really bad, when it comes to explaining smth, so i also made a shitty illustration. Enjoy! P.S.: there's was a video of it made in Gmod, but Gmod is not real life so it doesn't cout + i couldn't find it

Drop a cube through a portal
>cube exits the portal at the same velocity that it entered

Drop a portal around a cube
>cube exits the portal at the same velocity that it entered

B

Stationary Block vs. Mass-less portal

M1(V1) = M2(V2)
M1(0)=(0)(V2)
0=0

A

>>9891268
That's a neat assumption, but not backed by evidence in game or in sr. Imagine there is no portal.

Anyone will tell you the ramp and the platform are in the same frame.

>>9891320
If the portals are not opposite each other, the velocity will change. For the same reason, momentum is not conserved.

You are disqualified from further posts.

>>9891352
The portals are not opposite of each other.

>>9885756
GLaDOS says in game that they do. That's how you're able to "fling" yourself after jumping into a portal at the bottom of a pit.

It would be A.
Just imagine dropping a hula-hoop around a basketball.

>>9891464
Consider an object in free space with two portals on it, at right angles to one another. Another object flies into one portal and out the other. The object with portals on it does not feel a force, because the second object does not accelerate at all, but momentum before is not equal to momentum afterwards, as a vector quantity it changed direction. Hence momentum is not conserved.

In the same vein of thinking, portals at different altitudes on a planet will have different gravity gradients, thus violating gravity being a conservative force and violating the conservation of energy.

The "dropping a hula-hoop" idea assumes the hoop stops at the bottom. But under your situation there would be a difference between whether the hoop stops or not, when in reality at the other side of the portal it doesn't matter which of the two happens because the box is already though the hoop portal. From the blue portal's POV, the box travels through it at constant speed, and there's no force whatsoever to slow it down.

Another way to look at it is that there's no difference between the orange portal being dropped down over the box and the box being dropped into the orange portal.

>>9891666
>666
evil trips confirm, B

Your friends are idiots and they deserve you.

>>9891375
Right. Therefore, the velocity and momentum of the object is different when it enters vs. When it exits.

It's not hard to understand

It is B it has been scientificially proven whoever thinks otherwise is a brainlet

>>9885756
This would mean after using portal you would be smashed by earth into dust or be thrown away in outer space in a milisecond since earth has momentum and you lose it entirely

>>9892484
>and you lose it entirely
That's not what he said, though

>>9885437
Anyone who doesnt answer either
>impossible to answer/violates physics
Or
>B
Is straight up pants on head retarded.
>but muh dropping a hula hoop over the cube arguement
If you drop a hula hoop over the cube, the cube exits a hole that is not stationary. It has to be B, because if you are only watching from the reference frame of the exit portal(forget whatever is going on at orange) you would see a cube exiting a hole at some velocity before its even all the way through the portal. That velocity multiplied by the cubes mass would give you its momentum. I guarantee you this number isnt zero, which means the cube launches proportionally to the velocity of the entrance portal. The orange plaform would experience a resistance proportional to the mass of the cube and the force of gravity. This means the cubes energy is obtained from the velocity of the orange portals platform.
>but it cant transfer energy without touching the cube!
Wrong. I can transfer energy from one magnet to another without them touching eachother, the “medium” through which this energy is transferred is the electromagnetic field. In the case of OPs portal question, the energy would be transferred via spacetime itself.

>>9892528
Nice try, but imagine the orange portal is so big that you can see the blue portal and the cube when you look in to the blue portal. Then you will see the cube and the blue portal getting closer and closer to the blue portal.

In this example, every frame will see a cube with 0 speed relative to the blue.

>>9892559
>In this example, every frame will see a cube with 0 speed relative to the blue.
That's not right.

Reminder that there is no such thing as absolute velocity or absolute momentum. Both velocity and momentum are defined relative to some other thing, not to the aether. Which means that any argument that talks about preservation of absolute momentum is bonkers.

Note further that in the actual game, portals do not preserve momentum relative to earth / surrounding lab; this can be seen unambiguously in flinging levels, where your direction-relative-to-earth when you enter the portal can be completely different from your direction-relative-to-earth when you exit the portal.

Indeed, the only form of preservation of momentum in the game --which GLaDOS refers to-- is that portals preserve momentum relative to the portal surface. That is, when you enter the orange portal and leave the blue one, your momentum relative to the orange portal before you enter is equal to your momentum relative to (the back side of) the blue portal after you leave. This is the behavior you see in flinging exercises.

Applying this to the OP's scenario yields B. A is physical nonsense.

>>9885437
It would be B.

Consider that when the orange portal moves towards our companion cube, the universe contained within the portal on the other side moves down with the same velocity as the portal itself, relative to the cube.

When the companion cube passes through the orange, it does not have any initial momentum in technicality, but the "universe" around it does, therefore it appears to have momentum relative to that universe. Thus, when it has fully crossed the portal, it continues moving with said relative momentum.

It is important to note that of course the two portals are in the same universe, however moving one portal moves the space around it relative to the other portal. In this case this is orange and blue respectively.

Thus, it would be B.

QED

>>9892559
>Then you will see the cube and the blue portal getting closer and closer to the blue portal.
>In this example, every frame will see a cube with 0 speed relative to the blue.
These two statements contradict eachother. You cant have something get closer to x without having velocity(or speed as you call it) relative to x.

>>9892566
>>9892604
What you see looking in to the blue portal has nothing to do with the placement of the blue portal itself.

Relative to the orange portal/piston, the platform/cube AND the wedge/blue portal are moving at the same speed.

>>9892657
Well, they both are, and aren't, aren't they?

>>9892179
Hey idiot, the frame of reference of the block entering the portal is that of portals opposite of each other.

>>9892779
And from the frame of reference of the block it will keep moving at the same speed.

>>9892779
>>9892787
The portal is at an angle on the wedge, it wouldn't go straight up. If it was flat on the ground, I'd agree.

>>9892672
If you're trying to say that there exists a frame in which the cube has 0 speed relative to the blue portal/wedge then yes.

It doesn't matter what speed the cube has relative to the blue portal, since it's going into the orange portal at speed v.

>>9892959
I'm saying that, if one portal moves and the other does not, then relative to both portals, everything is both moving and not moving, depending on which side of the portal you're on. There certainly exists a frame in which the cube has 0 speed relative to the blue portal but it is not the most relevant one.

Anyone here low dimensional topologists? I really like the field but it seems to be shrinking. No one seems to care about 3 manifolds anymore after Ian Agol's virtually Haken proof and the solution of the Poincare conjecture by that russian autist.

If you are, what are you working on? Are 4 manifolds more "in" right now?

>>9893405
>>9893937
That's a fair interpretation. I dont like it, but it is fair.

this question is a brainlet filter because its jibberish and there can be no answer

this thread exists so that smart people can laugh at idiots who arent smart enough to realize its a joke.

>>9894932
Doesn't stop it from being a weekly fucking thread.