I love this comment section. Perfect balance of people actually trying to discuss and people getting pissy because their answer can be the only right one.
I don’t know shit but when I try and picture it happening in my head I can only see A being correct, think Doctor Strange portals. When he moves a portal the person comes out stationary
I believe it should be A. People aren’t moving, and the portal doesn’t carry momentum. At most people would be appearing on the other side with very little delay between eachother resulting in the most recently teleported person violently pushing away the last one.
With the tennis racket analogy both portals would be moving. In the thought experiment from the image just one is moving, resulting in an unaccounted for momentum, unless the people shoot out the blue portal
How can it not be b? Every situation in the Portal games is already exactly like this, but with the portal fixed to a slab that moves with the rotation of the Earth, whereas in the drawing the portal moves as the sum of earth rotation + the movement of the train.
But if we use coordinates relative to the orange hole, the whole world, including the rails and people on them, is moving, and the people are moving towards the hole with a speed of the train.
But, “speedy” relative to what? Relative to the walls of the room your are inside? What if you are in a falling elevator? Relative to the rotating surface of the earth? To the center of the solar system? “Relative to the portal” is the only answer to that question that makes sense.
If the blue exit portal was behind the wagon and so moving at the velocity of the orange entry portal, then I would agree that it’s A because they move at the same velocity and in the same direction.
But since the blue exit portal is static and the orange one is moving, the people will enter the portal at a relative velocity to the portal which will be transferred to the blue one. Meaning B will occur.
If the portals were on two wagons going in the opposite directions at the same X velocity, then the people would enter at X relative velocity and exit at 2X velocity.
The portal is a hole. The hole is moving. The conservation of momentum is the hole moving as it continues to move along the track. If the people start moving, where does that momentum come from?
Imagine a tennis racket with no strings. Two portals are stretched across the space the strings would normally be, back to back, one orange one blue. If you threw a ball in the air as if you were going to serve and swung the racket, the ball would pass straight through the portals as if they weren’t there and would fall straight down due to gravity. The ball maintains its conservation of momentum, and the tennis racket holding the portals also maintains its conservation of momentum as it swings through the air. There is no force applied by a hole.
Lets say the tennis racket has 2 portals. One in the front and one in the back. When you swing the racket, the front portal moves forwards with some speed V. The portal on the back is moving backwards with the same speed, so -V (same speed V, but in opposite direction). A stationary ball, suspended in mid-air would have 0 speed. The racket portal approaches the ball at speed V, so the ball has a relative speed V to the racket. The portal on the back has a speed of -V and ven you combine that with the ball’s speed of V, we get -V+V=0. And so the ball stays put. The portals in the image are not both in motion. The front portal is approaching the people with a speed of V and so the relative speed of the people to the portal is V. The exit portal has a speed of 0, relative to the people. When the people go through the portal, their speed is 0+V=V, meaning they get launched out the exit portal with the same speed the entrance portal hit them.
Interesting way to look at it, but I still dont see where the force is acting on the object going through the portal. The object is not in motion and will stay in that state unless something acts upon it, so where is the energy coming from to act on the object?
To make it clear from the start: I agree 100% with B - there has to be movement, because without it, people wouldn’t come out of the portal at all. And if there is a movement, then the only reasonable speed would be that of the train.
But: Your question about the energy is still interesting. It must come from somewhere. And I think, the only source, from which it can come, is the train. That is, the train would lose energy and therefore slow down.
Do we agree that the massive block with the blue portal is not moving? So, imagine we are standing right in front of it when it happens - what happens exactly? How do the people appear?
The people appear because the orange portal is moving towards them, the people then, like through a moving door, just pop out the other side.
It’s a door way through space, not a momentum giving portal.
Can you not see the orange portal moving? They don’t jump through it, this carrying their own momentum through. They are stationary through it so coming out they will also be stationary
Of course I see the orange portal moving. So we agree the orange portal is moving, the blue is stationary.
So, when you’re saying “the people just pop out the other side”. What does that mean? Do they pop out one by one? So one moment, no one is there, the next moment one person spawns and after that the third person spawns? Or do they spawn altogether? Or does each person come from the portal centimeter by centimeter, atom by atom - pushing through the portal?
That’s not what I mean. Let’s just look at one person: the person will not just appear as a whole at the blue portal, right? First there will be, I don’t know, the left arm, then the left side of the torso, the middle part… and so on. That’s what I meant with centimeter by centimeter, atom by atom - pushing through the portal. Would you agree?
At least that’s how it’s in the game. It’s not that you are touching one portal, despawn and appear at the other portal, right?
Yeah they kinda lose ground under them as the portal goes through them, they aren’t pushed, they are moved through space. No additional force or momentum is ever applied.
In the game you aren’t pushed through ever, you walk through or fall through them. You appear at the other side of the door.
So, you say, they are moving without speed. Which could only mean when one person touches the portal in one millisecond, his complete body just disappears completely from the rails and in the same millisecond his body appears behind the other portal.
That’s not how portals in the game work. That’s rather how the transporter in Star Trek works.
Who even said anything about teleporting the whole body?
The portal is moving into him so as the parts of him go through they appear on the other side like a door
Think of it as a portal falling on you and another on the floor next to you, as it falls your head goes through and your head appears through the portal on the ground and the rest of the body goes through as it falls until the portal lands on the floor and you’re standing on that same floor but in the other place as the portals are still connected.
Nobody said it’s teleporting the whole body. But that was my only explanation of how something can move without speed.
But great, that’s what I wanted to clarify the whole time. I think my explanations were too complicated, sorry.
So, taking your example:
When the portal falls on me - as soon as it reaches my neck. Only my head is coming out of the other portal, literally right above the ground. Correct?
As the portal keeps falling down, more and more of my body comes out of the other portal until my whole body is out of it. Correct?
Which leads to the fact that my head was moving from right above the ground to the height of my body. Correct?
So my head moves upwards. And since it takes time for my head to move upwards, we can measure the speed of my head moving upwards. Wouldn’t you agree?
Yeah the falling down portal does help a lot with explanation imo
we can measure the speed of my head moving upwards. Wouldn’t you agree?
Fair point, we can measure that, it would match the speed of the portal falling. It still won’t launch the person as it isn’t transferred but you can certainly measure the speed of the portal using it.
That’d be gravity. But the difference is that we are not moving (at least not relative to the ground) before entering the portal, so gravity just keeps us at the bottom.
After entering the portal, we are having a movement to the speed of the entering portal as we already established. So, gravity has yet to work against this motion (which will, of course, eventually keep us on ground again because gravity does its thing. But temporarily, and depending on the actual speed, we might have a bit of air time in this scenario).
I have my doubts, that this will convince you now. However, I gotta say, it was a lot of fun discussing this completely speculative topic with you. Also, I give you, that - while I’m still 100% sure that B is the only sensible solution for this question - you helped me better understand why people might think A is correct.
Dont they need to be hovering mid air for either to happen? I am trying to imagine how would a moving portal teleport a person laying down without teleporting the ground beneath him. I think neither a or b would happen, I think they would be draggen on the ground and splattered, but if I HAVE to choose, I say A is more likely. Because they are laying and not hovering I dont think they will be launched.
However, the portal is moving. So if we look at this relative to the portal, they would moving into the portal. I imagine they would get shot out along with the rails. Of course, they’ll eventually plop back down, so it really could be A if the trolley was moving quite slow.
I agree, in the portal game they would be scraped/blended on the bottom of the support of the portal attached to the train. If they were in fact hovering in line with the portal I’m leaning towards, an object in motion will stay in motion. Given portal orange is moving and blue is stationary, objects entering the portal will exit at the same velocity and b would probably happen in game.
my brother came up with a great analogy - say you’re falling and there’s a portal below you also falling, just slightly slower than you. when you eventually fall through it - do you come out falling slowly or quickly?
it would have the be quickly. even though you and portal are moving slowly relatively to each other, your individual momentum is conserved, the movement of the portal is irrelevant.
Except there is no concept of “individual momentum,” it’s all relative to something. Not to mention, technically speaking, any specific reference point that isn’t the blue portal will actually show it has infinite speed as it instantly moves from one spot to another. I think the most intuitive answer is to imaging standing in front of the blue portal, and look through it. From your perspective, the victims are being hurled at you, propelled by the ground. As soon as they go through the portal, no linger being in contact with the ground, they are effectively projectiles. By no means a hard proof, but this video has a compelling argument for that interpretation.
in my interpretation of how portals work - by joining space together - moving through a portal doesn’t involve infinite speed because you haven’t moved - the portals have just changed the space you occupy.
a bit like the inertialess/ Alcubierre drive where you travel faster than light without breaking any laws because you’re not moving at all in your space, it’s just that the space you occupy changes.
in the reasoning the people hurling towards the portal only appear to do so, once they pass through the portal they’ll be as immobile as they were before entering it.
the minute physics video is fun though. love their stuff.
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