I has confuse

[Vegeta897]

It is simply re-oriented and re-positioned in accordance with the angle of the blue portal.

Why does it have a new orientation? Because the portals are in different orientations.

Why does it have a new position? Because the portals are in different positions.

Why does it have a different speed? Because the portals are at different speeds.

 

[Higlac]

The brokenness of the physics of Portal notwithstanding, the statement "speedy thing goes in, speedy thing comes out" tends to imply that the law of conservation of energy exists in that particular universe. The energy required to propel the cube at any velocity must come from somewhere. Either the energy must be provided by slowing the orange portal, or must be manifested from it's surroundings. There is absolutely no evidence to support that the cube or the portals are energy vampires.

That is assuming that the portal stops moving because the platforms collided and not through any interaction on the part played by the portal.

Surely we have some modders on the forums, can someone make a custom map?

 

[Vegeta897]

You ask where the new velocity comes from. I can ask you where the new position, or the new orientation comes from? That's just what portals do.

This ball is both 25 meters and 10 meters away from the star. How can it be both? Because of portals. An object can have two different relative positions, orientations, and speeds to another object in the same world. Because of portals. If the orange portal in that picture was moving toward the ball at 10m/s, the ball would have a relative speed of zero to the star, and also a relative speed of 10m/s. If it goes through the portal, it's going to keep that 10m/s relation to the star.


EDIT: Aaand yet another example, viper sent this to me.

Say you shoot a bullet at a portal'd surface that is moving away from the bullet at 1m/s less than the bullet.

You guys are saying that once the bullet reaches the portal, it will shoot out of the blue portal at a full 900m/s, because that is the exact speed it had relative to the world.

Think about how weird this would look, when you are looking at the blue portal. You look and you see the bullet slowly approaching at 1m/s. Then once it hits the portal, it shoots out at full speed? That's just crazy.

 

[Higlac]

Yes, they have two relative positions and orientations, however, that does not explain why one object can manifest the energy to propel itself like that. Portals can account for there being two sets of position and orientation, they do not account for a change in those factors.

 

[Vegeta897]

Portals can account for there being two sets of position and orientation, they do not account for a change in those factors.

I didn't say there was a change. Just like there isn't a 'change' in position. There's two sets of velocities, just like the sets of position and orientation.


Also I have an extension to the bullet example.

If I'm sitting near the blue portal, looking at the bullet as it approaches me, I could reach into the portal and grab it. This is because the part of my arm that goes through the portal is now travelling at 899m/s. But the rest of me isn't. Do you deny this? If you do, then are you saying my arm would get ripped off or something if i stuck it through? Why? That seems like a rather chaotic set of rules in comparison to the simple ones I'm proposing. If you aren't denying that I can reach in and grab the bullet, then where is the speed coming from that lets the part of my arm in the portal go 899m/s? Since you guys think there has to be some force that causes my arm to do that. What is the force? Where does it come from?


If I stick my arm through the stationary portal, the part of my arm that is through the portal will be moving, because the portal it's coming out of is moving. You can't deny this. Nothing would be 'pushing' my arm back out of the portal. I can keep my hand in there provided the moving portal doesn't lead me to an obstacle that my hand runs into it and forces me back out.

So what force is causing my arm to move? Why?

How can my arm be stationary from my point of view looking through the portal, yet moving in the world? Because the portal is moving.

 

[Krynn72]

his is because the part of my arm that goes through the portal is now travelling at 899m/s. But the rest of me isn't.

If your arm is travelling 899m/s on one side of the portal, wouldn't that speed transfer to your arm on this side of the portal once you pull it back out, if what you're saying about the box/bullet is true?

 

[Vegeta897]

Uh, no? That is what would happen if what I was saying WASN'T true. If I pull my arm back out at say 5m/s, then my arm is coming back through the portal at 5m/s relative to the portal, and so everything would be fine.

According to the other people though, my arm should be coming out at 904m/s, because that's its "actual speed", even though I'm only pulling at 5m/s. Thus you have the catastrophic contradiction.

I didn't say the proper outcome of the bullet scenario; what would happen is the bullet comes out of the portal at a mere 1m/s and falls to the ground. Because that was the bullet's speed relative to the portal.

 

[Bad^Hat]

We were talking about this in chat, and the more I think about it, the more I think that portals like this just shouldn't be allowed to move through space. The effects it would have on the material world and any object travelling through it seem too mind-bending to imagine as real, so I'm hesitant to think there's actually a sufficiently logical explanation for this (ignoring that it couldn't happen, of course).

I am beginning to think that Vegeta's explanation is the tidier solution, though, for one basic reason - the way in which objects would have to 'travel' between the two points on a material level. Someone brought up the point in chat that if you had an object travelling at 10m/s towards a portal which was also moving towards the object at 10m/s, it would have to exit the stationary portal at 20m/s. If you try to imagine the object entering and retaining it's velocity of 10m/s on the other side, you have to imagine that the object becomes compacted in some way as it's still technically entering at 20m/s, which is ludicrous. You could ignore this effect if you said that the object simply emerged from the stationary portal at 20m/s in order to come out whole, but then instantly returned to it's original velocity once it was 'complete,' but I can't imagine how this would occur either. When you think about something like this, it becomes a little more difficult to imagine the portals as simply a 'window' in space, as I had originally thought.

This becomes even more mind-bending when you apply non-linear speed to the portal or the object, or both, since any momentum already acting on the object would be acted against by the path of the portal relative to space... or something. I'm not even going to attempt to imagine both portals and the object moving. Anyway, returning to the original example, one curiosity to consider: what if the piston carrying the orange portal were to cease movement abruptly just short of halfway down the box? Would the momentum acting on the top half carry it the rest of the way, causing it to appear as though it were being 'sucked up' by the orange portal? This is the kind of thing that makes me a little unsure about either explanation, and you could get even sillier with it if you wanted to (but I won't).

Anyway, it's possible that I'm over-complicating or over-simplifying, or just fungling the physics altogether. I don't know. My brain hurts.

 

[Schweppe]

I have to say, Vegeta has totally convinced me of his viewpoint. I feel violated

 

[ríomhaire]

Vegeta in your first animation with the box flying off the pole the second one with the box staying in place actually does seem perfectly reasonably depending on how you consider portals to work. That said the space scenario occurred to me last night in bed and I guess that proves it. The orange portal would in this case have to force the blue portal out. I guess portals cause a non-inertial frame

In any case I'm pretty loath to admit you're right because you've been quite arrogant about this and I still think your "two worlds" perspective of it is very flawed, but the space scenario does clinch it.

 

[MuToiD_MaN]

Vegeta wins by Flash maneuver! As per usual. Portals break the laws of physics, especially conservation of momentum, and when they're broken, it's all or nothing.

 

[Vegeta897]

In any case I'm pretty loath to admit you're right because you've been quite arrogant about this

Haha, in what way? I wasn't the one trying to laud my education over you, as if that makes what I'm saying 'more right', or that I was offended by the fact that you disagreed with me simply because I was a physics student (your words exactly)

But, I won't deny that I can be an arrogant person.

and I still think your "two worlds" perspective of it is very flawed

How? I know you don't like the idea, but nothing about it causes any 'flaws', and it helps to understand how an object can have two different sets of relatives to a single world. Each set of relatives could be thought of as a sub-world. I'm not saying that by entering the portal you're 'leaving' the first world; you're still in it, obviously. You're always in both, just in different locations/orientations/speeds.


But anyway, I was having so much trouble getting to sleep last night because I keep thinking of scenarios that further supported my view, and I kept arguing with imaginary people in my head. I was dreading coming to this thread and seeing you specifically Riom continuing to argue against what I was saying (despite being pretty confident in my last posts) and so I'm so damn relieved I don't have to continue this awful shit.

I was arguing with Kinetic a ton in steam chat last night, I wonder what he'll say about this.

 

[ríomhaire]

Haha, in what way? I wasn't the one trying to laud my education over you, as if that makes what I'm saying 'more right', or that I was offended by the fact that you disagreed with me simply because I was a physics student (your words exactly)

I was offended because you said I didn't grasp the basic concepts of relative momentum.

 

[Krynn72]

Uh, no? That is what would happen if what I was saying WASN'T true.

Touche salesman. I went to bed this morning thinking you were wrong, but now that its not 4am in the morning, I understand exactly what you're saying. I am in agreement. Vegeta wins another one of these threads!

 

[Vegeta897]

I was offended because you said I didn't grasp the basic concepts of relative momentum.

My bad then What I should have said is that you weren't correctly applying the basic concepts of relative momentum.

Also stop saying I 'won' the thread, you guys make it sound like I'm acting all triumphant I'm trying to be as humble as possible here!

 

[Viperidae]

Vegeta had my moral and intellectual support. I'll take the winning trophy in his place.

GLOATGLOATGLOAT

 

[Vegeta897]

We were talking about this in chat, and the more I think about it, the more I think that portals like this just shouldn't be allowed to move through space.

But everything in the world is already moving. Not relative to the Earth, sure, but the Earth itself is moving, as is the sun, as is our galaxy.

Unless you mean, portals shouldn't be allowed to move in relation to eachother. But I still don't see any reason why not. At the end of Portal 2 you

Spoiler

shoot a portal on the moon. The moon is definitely moving in relation to the Earth,

so that right there proves it's possible even in game-canon.

what if the piston carrying the orange portal were to cease movement abruptly just short of halfway down the box? Would the momentum acting on the top half carry it the rest of the way, causing it to appear as though it were being 'sucked up' by the orange portal?

If the part that went through the portal had enough inertia (weight times its speed) to 'pull' the rest of itself through, then yes. But it would be a reduced speed of course, because it had to use some of its momentum to pull the stationary half of itself through.

 

[Krynn72]

Wait, i've gone and made myself unsure again.

Vegeta, I demand you tell me what happens in each of these scenarios:

 

[Vegeta897]

These scenarios are kind of ambiguous, and it's hard to show with words what will happen.

In A, does the piston keep going? He won't be 'sucked in'. His upper body will have the 10m/s speed, and that will try to pull his lower half right at where the portal 'split' is, but it may or may not be enough to pull him all the way through. Just like if you have a portal on the ground and the cieling, and you slump one end of a bendy object like say a blanket inside the portal. The gravity pulling on the half that falls through the portal might be enough to pull the rest of the blanket through the portal. Same concept here, except replace gravity with the horizontal velocity caused by the moving portal.

What you wrote in B is correct. If he's latching on to the piston wall like that, the part that is through the portal is stationary in the world, yet remains attached just fine to his lower half as it moves. Pretty basic.

As for C, if you jump at a portal that is coming at you, you'll come out of the stationary portal with a speed of your speed + the portal's speed.

And I already answered your bonus question when I responded to Badhat. And sort of in my answer to A.


If I stuck my arm out and a portal came at it at like 1000m/s and stopped right at the point where it only engulfed my arm, then it would probably tear my arm off. It would be as if that part of my arm suddenly gained the momentum of 1000m/s. Whether my arm is strong enough to stay together and pull the rest of me through or get torn off is arbitrary.

 

[Krynn72]

Ok, as I thought. So the moral of the story is never jump through a portal moving towards you, just grab onto the platform first, then let yourself through. You never know when that information might come in handy, thanks!

 

[StarBob]

I just now noticed this thread and haven't really read any of it, but I just want to type stuff.

From what I've seen I feel like A would happen in game because the portals act essentially as a window between two points. Their movement would be irrelevant to the game's calculations as to what the object going through them is doing.

The rest is confusing. At first I thought it would still be A in reality because of the nature of the portal essentially acting as a two dimensional object... so no matter what the scenario energy could not be transferred between them. Basically using he scenario of something like... a person outside of a spacecraft with an open door, then the entire universe moving everything except the person so that they're inside the spacecraft wouldn't make the person continue moving once it stopped. However then I was thinking about how the piston moving down would displace air and the air on the exit of the portal would have a positive pressure (as more air moves through it) and thus it would basically act as a pump... creating a vaccuum. Then I figured that if the matter that is the air would be moving through the portal relative to the exit, then any matter would...

I'm not sure what's most reasonable though. It just seems like movement requires energy and there's not really any energy occuring.

 

[Viperidae]

It's definitely messy and breaks all laws of physics. We've known since Portal 1 that they can create perpetual motion loops.

 

[Vegeta897]

Vegeta wins another one of these threads!

You never know when that information might come in handy, thanks!

This is how you make me feel.

http://www.pixelatomy.com/stuff/krynndoggy.swf

 

[Doomination]

I have a corollary for this:

http://www.freeimagehosting.net/uploads/5d08128ad3.gif

what would happen in this instance?

 

[Vegeta897]

Pretty much exactly what happens in that gif. Which is basically the same thing as if the portals weren't even there, just 2 walls coming in on you.

 

[ríomhaire]

Unless you mean, portals shouldn't be allowed to move in relation to eachother. But I still don't see any reason why not. At the end of Portal 2 you

Spoiler

shoot a portal on the moon. The moon is definitely moving in relation to the Earth,

so that right there proves it's possible even in game-canon.

Here too, and more obviously.

Spoiler

http://www.youtube.com/watch?v=IcLHaU6EVo8

 

[Vegeta897]

Oh shit, I totally forgot about that part.

Right, so if you through an object into a stationary portal and it came out a portal that was moving 10m/s upward, the object would gain that 10m/s upward velocity when it came out. There is no identifiable 'force' that gave it that velocity, it's just the way moving portals work.

 

[Bad^Hat]

But everything in the world is already moving. Not relative to the Earth, sure, but the Earth itself is moving, as is the sun, as is our galaxy.

Unless you mean, portals shouldn't be allowed to move in relation to eachother. But I still don't see any reason why not. At the end of Portal 2 you

Spoiler

shoot a portal on the moon. The moon is definitely moving in relation to the Earth,

so that right there proves it's possible even in game-canon.

Look, no, agh. We were discussing this as if it were in real life (except not really), you already acknowledged that objects wouldn't have this reaction in the game, so I don't know how the game canon is suddenly being put forth as proof. Anyway when I say they shouldn't "move" I'm imagining them in a vacuum, as that's really the only way you can neatly assess a problem like this - and like I already said, it can't really be neatly assessed, not absolutely. I merely said yours was the tidier solution as it didn't involve objects getting crushed as they passed through... but now I realise it actually means they can be torn apart, so it's on about even footing as far as maintaining the integrity of objects that pass through it.

That's a problem if you're trying to view the portals merely as a "hole" in space, as the hole itself shouldn't impart any energy on anything that merely crosses it's threshold. I realise you already have problems like perpetual motion breaking conservation of energy, but as I demonstrated in my post there are infinite amounts of bullshit you can come up with that have no rational (or at least easily explainable) explanation. You're not proving your point so much as saying "it doesn't make a heck of a lot of sense for it to happen any other way." Well, no way makes a heck of a lot of sense. I don't see what makes one set of physics-breaking propositions more accurate simply because they're more intuitively coherent. Granted, accuracy may not actually be the goal here as, well, it's impossible after all.

 

[Vegeta897]

you already acknowledged that objects wouldn't have this reaction in the game,

Because of the engine limitation, not by design.

so I don't know how the game canon is suddenly being put forth as proof.

Proof that you can have moving portals. Not proof that everything I said in the thread is right.

I merely said yours was the tidier solution as it didn't involve objects getting crushed as they passed through... but now I realise it actually means they can be torn apart, so it's on about even footing as far as maintaining the integrity of objects that pass through it.

They're getting torn apart for a good, natural reason. If one of the portals is going fast enough to tear an object apart, that's to be expected. You can't suddenly accelerate an object that fast in an instant and expect everything to be hunky dory. It isn't anything like how messed up and unnatural it would be if an object can enter a portal at one rate and exit at another rate.

That's a problem if you're trying to view the portals merely as a "hole" in space, as the hole itself shouldn't impart any energy on anything that merely crosses it's threshold.

The hole itself isn't imparting energy. The change in relative speed is what imparts the energy.

but as I demonstrated in my post there are infinite amounts of bullshit you can come up with that have no rational (or at least easily explainable) explanation.

Where? I don't see anything you came up with that doesn't have an obvious answer. Are you talking about the stopping half-way thing? What about my answer to that confuses you? You subject half the object to a higher relative speed, it's going to behave as if that half of the object suddenly has that amount of inertia in the given direction. If this higher relative speed is very, very high, then it may be enough inertia to either pull the rest of itself through the portal, or separate entirely from itself. Just like if you yank someone's arm off really fast, you're subjecting sudden inertia to their arm while their body is stationary. Yeah, that's 'messy', but it's not physics-defying messy. It can happen in real life and be understood in real life physics. There's no 'warping' or any other nonsense that is physically impossible going on.

You're not proving your point so much as saying "it doesn't make a heck of a lot of sense for it to happen any other way." Well, no way makes a heck of a lot of sense.

Every single situation I've posted works out cleanly, and it makes sense. Maybe you're not fully understanding it if you still think it doesn't make 'a heck of a lot of sense.' There really isn't much I can say.

 

[kineaesth]

I was arguing with Kinetic a ton in steam chat last night, I wonder what he'll say about this.

~

Portals break the laws of physics, especially conservation of momentum, and when they're broken, it's all or nothing.

It's definitely messy and breaks all laws of physics.

the box staying in place actually does seem perfectly reasonably depending on how you consider portals to work

Utterly unsatisfying explanations - "we don't know how it works, it disobeys multiple sets of rules, so if we assume it works like this, then certainly, the box must fly out!"

My bad then What I should have said is that you weren't correctly applying the basic concepts of relative momentum.

Or perhaps the basic concept of conservation of energy in a closed system...
HOLD ON

It isn't anything like how messed up and unnatural it would be if an object can enter a portal at one rate and exit at another rate.

Man, this is totally correct! Closed system, no net force, static object suddenly getting accelerated, that is messed up. But then

There is no identifiable 'force' that gave it that velocity, it's just the way moving portals work.

ad hoc

The hole itself isn't imparting energy. The change in relative speed is what imparts the energy.

How? I can't accept an explanation with all these bizarre "mystery-forces" at work.

There is no identifiable 'force' that gave it that velocity, it's just the way moving portals work.

Can I say ad hoc one more time? ? ? AD HOC





coda

Maybe you're not fully understanding it if you still think it doesn't make 'a heck of a lot of sense.'

:x

 

[Light_Science]

''A'' is the right answer in real life.The portal is pushed to the cube,the cube is not forced into the portal.If the cube was forced with speed into the portal then this will create a gravitational slingshot !

 

[bones_taw]

Gotta say B.
Shouldn't really matter if the Block is moving or the portal. Relative velocity is still there.
Since the portal moving down 'slams' into the platform with block, then we assume it doesn't slow down or stop until after block has entered portal.
PS I was a Rocket Scientist at Aperture for several years so I know what I'm talking about.

 

[ríomhaire]

BatHat, this is something that should have occurred to me earlier but I just forgot about it to be honest: sometimes forces in reality are not conserved in every reference frame. The coreolis force is an example. From the Earth's rotating reference frame there is no apparent cause but it.s still there.

 

[bbson john]

There is moving portal surface? where?

 

[bucketokarma]

Neither would happen in the game.... the portal on the moving surface would allow the box to come out of the sloped surface, but since the surface the cube is resting upon is flat, it will just stay in the center of the portal on the sloped surface until either, you grab it, or the piston, raises back up and the cube stays on the flat surface it was on originally. The cube was never in motion, so the thought of the cube flying out of the blue portal, just does not work. If, however, the moving portal slams the flat surface the cube is resting on hard enough to cause the surface to collapse, the cube might "jump" out of the second portal, but only relative to the amount of inertia the cube has, and how far/fast the surface it's resting on falls....

 

[ríomhaire]

There is moving portal surface? where?

8 posts above yours:

Spoiler

http://www.youtube.com/watch?v=IcLHaU6EVo8