[QUOTE=Tamschi;52150372]I don't think that's really related, since in that case you have a pretty conventional system. (The main issue is that you'd need a curved hole in all cases that aren't pole to pole.)
Otherwise you're definitely right though, if the portals are fixed to each other and act like a 'too short' tunnel then there's no weirdness in terms of conservation of momentum (but conservation of energy is still broken).[/QUOTE]
That's what I thought. So probably we're limited specifically by how the specific lore would explain a portal existing. If it's a short hole like what would conventionally make sense then there's nothing to worry about momentum wise.
But if say, they have to worry about transferring your atoms through them at speed, probably to assure nothing gets clogged in whatever sub-space hell exists between portals, then you'd see things being shot out at the speed they're forced through the portal (example B) as the portal would be essentially sucking in whatever touched it. Basically if you shove your arm into the portal, all of you is going into the portal at that speed, or things are going to get ripped apart.
In the classical portal sense, such as the one given in Portal, you're able to stand half way through each portal, ergo we're having to operate on the short-hole scenario.
[QUOTE=Tamschi;52150344]Technically that's precisely the reason why it [I]would[/I] fling you out.
'Zero momentum' is very subjective even in our universe, and while games have a 'true' frame of reference for practical reasons, the physics are still usually invariant regarding its velocity (aside from air drag simplifications).[/QUOTE]
Yeah this is exactly it. Momentum is the product of velocity and mass, and there's no objective frame of reference for velocity. The interpretation that makes most sense for me is you measure the velocity of the cube relative to the portals, and I can't imagine how else you would define the momentum that needs to be conserved. Valve's Portal even tells us this is how it works, with the velocity of objects passing through portals being transformed based on the relative orientation of the portals.
[editline]25th April 2017[/editline]
If you believe A makes most sense, what would your answer be to this?
[QUOTE]What about if the entrance portal was on Earth, and the exit was on Mars? Does the universe care about the velocity of the portals relative to each other?[/QUOTE]
[QUOTE=F.X Clampazzo;52150396]That's what I thought. So probably we're limited specifically by how the specific lore would explain a portal existing. If it's a short hole like what would conventionally make sense then there's nothing to worry about momentum wise.
But if say, they have to worry about transferring your atoms through them at speed, probably to assure nothing gets clogged in whatever sub-space hell exists between portals, then you'd see things being shot out at the speed they're forced through the portal (example B) as the portal would be essentially sucking in whatever touched it. Basically if you shove your arm into the portal, all of you is going into the portal at that speed, or things are going to get ripped apart.[/QUOTE]
That last part depends on whether the portal is bidirectional. If these are Portal portals, then the space through them behaves normally and you can just pull out your arm.
Stargate is really inconsistent about the lore in this regard, iinm. Apparently objects that enter one don't experience time until they exit (some episode of I think Atlantis where one gets clogged), stuff that goes in the wrong way is destroyed, but you can also put your arm into the exit portal to trigger its safety and pull it back out later (Universe, an episode with an ice planet).
Well, if they work as short holes, then you'd just walk out onto mars with the same speeds at which your body was moving as it entered because there's no momentum to worry about, though you'd end up with maybe a slightly more forceful set of first steps since your muscles were moving to overcome earth's gravity and they're now subject to mars' gravity.
If we're saying that portals have to conserve all momentum, speed and mass from one end to the other, then you're going to get crushed on the edges of the portal or something because you're going to get flung in some funky direction due to planetary rotation, orbit speed, etc.
You could reasonably figure everything except the change in speed from planetary rotation based on the moon scene from portal 2, if it didn't model the aspect where all the atmospheric gasses were sucking into the vacuum of space.
[QUOTE=Tamschi;52150422]That last part depends on whether the portal is bidirectional. If these are Portal portals, then the space through them behaves normally and you can just pull out your arm.
Stargate is really inconsistent about the lore in this regard, iinm. Apparently objects that enter one don't experience time until they exit (some episode of I think Atlantis where one gets clogged), stuff that goes in the wrong way is destroyed, but you can also put your arm into the exit portal to trigger its safety and pull it back out later (Universe, an episode with an ice planet).[/QUOTE]
exactly, it's rather inconsistent, which makes answering the question hard because we don't have a consistent set of lore to answer with.
[QUOTE=F.X Clampazzo;52150431]If we're saying that portals have to conserve all momentum, speed and mass from one end to the other, then you're going to get crushed on the edges of the portal or something because you're going to get flung in some funky direction due to planetary rotation, orbit speed, etc.[/QUOTE]
Okay so here's the punchline: what are you conserving momentum relative to?
[QUOTE=Ziks;52149353]Imagine the piston is coming down super fast, like 200 Mph. Watching the orange portal, the cube would emerge at 200 Mph as it's "pushed" out. But then what do you think would happen when the piston reaches the floor? Would the cube suddenly decelerate and just tumble out as if the piston was only going 1 Mph? Or would the momentum of the cube relative to the portal be maintained?[/QUOTE]
Except the cube is not pushed, as there is no pushing of the cube. The cube would be moving only [I]relative[/I] to the portal, but since an object at rest tends to stay at rest, the only movement involved would be the gravitational effects on the cube as it passes through the exit portal, which would pull it downwards [B]not[/B] from the portal's perspective (that is, straight outwards) but towards the source of gravity, hence it would merely fall.
Imagine dropping a hula-hoop onto a cube so that the hoop falls [I]around[/I] the cube. The only difference here is the hula-hoop doesn't have some magical displaced exit point.
[QUOTE=Zero-Point;52150489]Except the cube is not pushed, as there is no pushing of the cube. The cube would be moving only [I]relative[/I] to the portal, and since an object at rest tends to stay at rest, the only movement involved would be the gravitational effects on the cube as it passes through the exit portal, which would pull it downwards [B]not[/B] from the portal's perspective (that is, straight outwards) but towards the source of gravity, hence it would merely fall.[/QUOTE]
Unless the universe this is in outright doesn't have atoms, and assuming there's not some other exotic back door, this outcome probably would induce nuclear fusion.
[editline]edit[/editline] Unless I'm misreading this, since this is [I]technically[/I] a description matching case B from earlier too.
[editline]edit[/editline] Rated programming king because I honestly can't tell what you're trying to say.
[QUOTE=Zero-Point;52150489]Except the cube is not pushed, as there is no pushing of the cube. The cube would be moving only [I]relative[/I] to the portal, and since an object at rest tends to stay at rest, the only movement involved would be the gravitational effects on the cube as it passes through the exit portal, which would pull it downwards [B]not[/B] from the portal's perspective (that is, straight outwards) but towards the source of gravity, hence it would merely fall.[/QUOTE]
If there is no pushing of the cube, why does it emerge from the portal instead of all its atoms being dumped on the plane of the exit portal with no velocity?
[editline]26th April 2017[/editline]
Ninja
[QUOTE=Ziks;52150511]If there is no pushing of the cube, why does it emerge from the portal instead of all its atoms being dumped on the plane of the exit portal with no velocity?
[editline]26th April 2017[/editline]
Ninja[/QUOTE]
For whatever reasons present that prevent any object passing through a portal from having all of its atoms dumped onto the plane of the exit portal with no velocity.
If the portal is to be considered a hole between two points, then having a velocity imparted on the cube with no physical interaction would violate conservation of momentum. Where would the energy be coming from? It certainly can't be from the piston moving, because there's no medium through which the piston (or the portal, which is, remember, essentially just a hole) can impart its energy into the cube, which is at rest, because the cube simply passes through the portal is though it were a hole, like one of my earlier examples where you essentially rapidly force an open door (or I guess door-frame to be accurate) onto an object: The door passes around the object, the object in question remains in place. Again, the difference here is that the exit portal can have an entirely different exit point while the door-frame cannot.
FantyM420's [url=https://facepunch.com/showthread.php?t=1554813&p=52149263&viewfull=1#post52149263]image[/url] explains it better.
I mean I get what y'all are saying about it having to exit the exit portal as the same rate that it enters the entrance portal, but that totally throws conservation of momentum out the fuckin' window because that implies that you can impart massive velocity into a lot of mass by simply moving a portal over it, which requires not nearly as much energy as it would to move the cube on its own.
I just wanted to point something out... If the piston is moving down, how does the energy transfer onto the object in the opposite direction of the piston? The top of the object is pointing towards the moving portal, the top of the object is then translated to the stationary portal first, where the top is pointing out from there, but due to conservation, the piston would transfer the energy downward on the object, not upward.
Also, wouldn't the portal just be pushing the air, so there's technically a hole there in the piston, so why would energy transfer in the first place? Sure, some energy, but a negligible air current.
My head hurts, please don't yell at me. :(
[thumb]http://i.imgur.com/AyAhfNs.png[/thumb]
Although I can see how an object translating through the exit portal faster would result in more momentum...
Be right back, going to find some drugs and test it for myself.
[QUOTE=Zero-Point;52150528]For whatever reasons present that prevent any object passing through a portal from having all of its atoms dumped onto the plane of the exit portal with no velocity.
If the portal is to be considered a hole between two points, then having a velocity imparted on the cube with no physical interaction would violate conservation of momentum. Where would the energy be coming from? It certainly can't be from the piston moving, because there's no medium through which the piston (or the portal, which is, remember, essentially just a hole) can impart its energy into the cube, which is at rest, because the cube simply passes through the portal is though it were a hole, like one of my earlier examples where you essentially rapidly force an open door (or I guess door-frame to be accurate) onto an object: The door passes around the object, the object in question remains in place. Again, the difference here is that the exit portal can have an entirely different exit point while the door-frame cannot.
FantyM420's [url=https://facepunch.com/showthread.php?t=1554813&p=52149263&viewfull=1#post52149263]image[/url] explains it better.
I mean I get what y'all are saying about it having to exit the exit portal as the same rate that it enters the entrance portal, but that totally throws conservation of momentum out the fuckin' window because that implies that you can impart massive velocity into a lot of mass by simply moving a portal over it, which requires not nearly as much energy as it would to move the cube on its own.[/QUOTE]
I suspect if someone were to run the numbers then you'd need a star's worth of energy to move one portal relative to the other or something. Anyway my point is that B conserves momentum whereas A does not. The cube doesn't change momentum as it passes through the portal, but it does change the frame of reference you intuitively use to measure its velocity.
[editline]26th April 2017[/editline]
Also the reason why atoms of objects passing through stationary portals don't all get dumped along a plane with zero velocity is the object must have non-zero velocity relative to the portal in order to pass through it. Shouldn't that also be the case when it's the portal moving over a stationary object? The atoms of the object have non-zero velocity relative to the portal, so shouldn't that be conserved on the other side?
[editline]26th April 2017[/editline]
Conserving momentum is a noble aim, but you need to define how you are measuring the momentum you want to conserve. What is the velocity of the object relative to?
Updated list of topics to avoid in WAYWO:
* Tabs v. Spaces
* Indentation Style (K&R vs GNU, etc)
* Moving Portals
[QUOTE=Ziks;52150308]What about if the entrance portal was on Earth, and the exit was on Mars?[/QUOTE]
[video=youtube;DAn87KyNjJ0]https://www.youtube.com/watch?v=DAn87KyNjJ0[/video]
[QUOTE=Fantym420;52149263]
So in the example animation the cube is resting on the platform, only being pushed down by gravity prior to portal contact. The piston comes down with the blue portal on it, but when it encounters the cube the piston makes no contact and imparts no force.
As the cube goes through the portal the forces on the orange side begin acting on the cube, and the cube starts appearing in the orange one, but it is still be held by gravity on the blue side. When a larger portion of the cube's mass is on the orange side, gravity would overcome the gravity on the blue side and it would tumble down the slope on the orange side.
Here is a rough sketch of what i'm talking about:
-img-
[/QUOTE]
This is the most correct as per portal 2's explanation of how they work. Besides, they specifically mentioned that you couldn't form portals on moving surfaces.
The disconnect comes from the two different intpretations where:
1) Portals are wormholes and do nothing but link otherwise distant spacial regions and orientations
or 2) Portals are objects which have their own velocity reference frames which must obey the conservation of force/momentum equilibria [I]including the portal [/I]when they move other objects.
The only thing that makes sense to me is that they are wormholes tied to objects of nearly zero mass. That would fix the "but earth is moving" argument.
[QUOTE=chimitos;52151057]This is the most correct as per portal 2's explanation of how they work. Besides, they specifically mentioned that you couldn't form portals on moving surfaces.
The disconnect comes from the two different intpretations where:
1) Portals are wormholes and do nothing but link otherwise distant spacial regions and orientations
or 2) Portals are objects which have their own velocity reference frames which must obey the conservation of force/momentum equilibria [I]including the portal [/I]when they move other objects.
The only thing that makes sense to me is that they are wormholes tied to objects of nearly zero mass. That would fix the "but earth is moving" argument.[/QUOTE]
But portals move in this section:
[t]https://portforward.com/games/walkthroughs/Portal-2/Portal-2-large-69.jpg[/t]
[QUOTE=paindoc;52150099]tbh this topic is making me want to start learning more of the formal maths too, since I plan on using traversable wormholes in the project I'm working on and I do like my hard sci-fi realities. This page was also exceptionally useful, and there's a link at the bottom to what seems to be a good textbook on this topic:
[url]http://www.webfilesuci.org/WormholeFAQ.html[/url][/QUOTE]
A couple of the Q&A in there seem to directly relate and might answer some the questions I'm seeing in here. Unless you want a much deeper dive into it, I think they were good enough? I'm not familiar enough with the material unfortunately to vet the answers. >.>
[QUOTE=Ott;52151149]But portals move in this section:
[t]https://portforward.com/games/walkthroughs/Portal-2/Portal-2-large-69.jpg[/t][/QUOTE]
Huh. Don't remember that bit. It's been a while!
Like Fantym said: it's a videogame! :v:
[QUOTE=chimitos;52151057]This is the most correct as per portal 2's explanation of how they work. Besides, they specifically mentioned that you couldn't form portals on moving surfaces.
The disconnect comes from the two different intpretations where:
1) Portals are wormholes and do nothing but link otherwise distant spacial regions and orientations
or 2) Portals are objects which have their own velocity reference frames which must obey the conservation of force/momentum equilibria [I]including the portal [/I]when they move other objects.
The only thing that makes sense to me is that they are wormholes tied to objects of nearly zero mass. That would fix the "but earth is moving" argument.[/QUOTE]
The FAQ I linked answers this question directly. Wormholes/portals can move and placing a portal on earth than on mars would be fine to transit between, as your reference frame would instantly change from that of Earth to that of Mars, so there'd be no artifacts of you suddenly changing your relative velocity and acceleration around the sun.
This is primarily because there is no true zero reference frame, as far as I understand it
[QUOTE=paindoc;52151303]The FAQ I linked answers this question directly. Wormholes/portals can move and placing a portal on earth than on mars would be fine to transit between, as your reference frame would instantly change from that of Earth to that of Mars, so there'd be no artifacts of you suddenly changing your relative velocity and acceleration around the sun.
This is primarily because there is no true zero reference frame, as far as I understand it[/QUOTE]
There we go, so that's B. And the Moon scene in Portal 2 is also B, since the surface of the moon has high lateral velocity relative to the surface of the Earth facing it but Chell comes out the other side with no sudden lateral kick.
[QUOTE=Ziks;52151765]There we go, so that's B. And the Moon scene in Portal 2 is also B, since the surface of the moon has high lateral velocity relative to the surface of the Earth facing it but Chell comes out the other side with no sudden lateral kick.[/QUOTE]
Except that's not how relativity works.
Two portals connect the spacetime of two distant places, causing their "frames" to become one. You can imagine this as both places existing at the same place at once, except that you can observe the other place only by looking through the portal. What happens is that when the portals do not move relative to their current frame, then both places act as if they're static to each other, despite the massive lateral velocity relative to each other.
Now this changes when one of the portals moves relative to its own frame. To make things easier we call the static portal A, its "frame" a, the moving portal B with the frame b. As an observer standing on the ground next to B, it moves relatively to b. Thus as an observer standing next to A, b is observed as if its in motion. What happens is that for the reality of a, the cube leaving through A already has a speed equal to the speed of the piston going down.
From where does the energy come from? It comes from the compression of spacetime that the cube experiences as it moves through the portal, similar but not entirely equal to how a warp drive functions.
In case things don't make a lot of sense, I'm trying to translate German terms into English.
Jelly stuff with LiquidFun
[vid]https://zippy.gfycat.com/RemoteInconsequentialBonobo.webm[/vid]
[QUOTE=Elec;52151816]Except that's not how relativity works.
Two portals connect the spacetime of two distant places, causing their "frames" to become one. You can imagine this as both places existing at the same place at once, except that you can observe the other place only by looking through the portal. What happens is that when the portals do not move relative to their current frame, then both places act as if they're static to each other, despite the massive lateral velocity relative to each other.
Now this changes when one of the portals moves relative to its own frame. To make things easier we call the static portal A, its "frame" a, the moving portal B with the frame b. As an observer standing on the ground next to B, it moves relatively to b. Thus as an observer standing next to A, b is observed as if its in motion. What happens is that for the reality of a, the cube leaving through A already has a speed equal to the speed of the piston going down.
From where does the energy come from? It comes from the compression of spacetime that the cube experiences as it moves through the portal, similar but not entirely equal to how a warp drive functions.
In case things don't make a lot of sense, I'm trying to translate German terms into English.[/QUOTE]
Maybe I read this wrong, but it sounds like you are exactly agreeing with me haha
[editline]26th April 2017[/editline]
Basically,
[img]https://files.facepunch.com/ziks/1b2611b1/portals.png[/img]
I understand what you are saying, I think, with the earth to mars experiment. That all objects on earth are moving with the earth and all objects on mars are moving with mars, and even though the portals are tethered to the respective planets an object moving through from earth(~30 km/sec) to mars(~24 km/sec) will end up on mars at earth's velocity. The object would go shooting out(~6 km/sec) and smash into anything in it's way, or just be ejected from mars if there is no object to hit.
If you went with this then portals would not work, thus destroying my fantasy with all your physics.
So, unscientifically( or just not discovered yet), I prefer to think that all objects entering and exiting portals keep only their velocity relative to it's planet. So if an object is at rest on earth its velocity relative to earth is 0. Then on mars when it exits, it would end up with a velocity that's 0 relative to mars.
The way i've thought of for this to work is portals are not flat, but instead egg shaped, it has an area of influence on each side which make the portal an ellipsoid and the portals them selves are a matched set of planes centered in this ellipse. This would allow the portal to rectify velocities between the two halves.
How do the portals rectify the velocity difference? Nano-bots, the matter/energy package shot out of a portal gun contains the materials to create a portal, and this includes nano-bots that line the edge of the portal and facilitate any calculations and energy redistribution that is needed. Also this is how they are linked, the bots facilitate that as well.
This might not make a lot of sense( or any), but this is just how my mind stretches to make this work.
This has been a fun discussion, and I kinda want to implement portals in my next project to play with these different ideas.
[b]Content:[/b]
I'm working on a new game after releasing Mine Field Crosser, this new game is a lot simpler, it consists of keeping a ball from touching the ground and also from flying off into space. Each tap of the ball pops it up, and depending on where you hit the ball from side to side as well. It's still in the early stages, but the two main challenges I've come up with are:
Clouds, these get in the way and stop you from tapping on the ball.
Gravity based taps, the higher you go the less gravity, less gravity means weaker hits on the ball.
You get points every tick, which is height times multiplier.
You increase the multiplier by 0.01 each tap on the ball.
Here's a few shots of it so far.
Just above start, the ground is below.
[t]http://i.imgur.com/RURTLkv.png[/t]
Transition area to super low gravity( a great place to raise the multiplier)
[t]http://i.imgur.com/7QNrfPy.png[/t]
The red zone, this is danger, half way in gravity stops and you lose the ball.
[t]http://i.imgur.com/jZZ99JO.png[/t]
[QUOTE=Fantym420;52152714]I understand what you are saying, I think, with the earth to mars experiment. That all objects on earth are moving with the earth and all objects on mars are moving with mars, and even though the portals are tethered to the respective planets an object moving through from earth(~30 km/sec) to mars(~24 km/sec) will end up on mars at earth's velocity. The object would go shooting out(~6 km/sec) and smash into anything in it's way, or just be ejected from mars if there is no object to hit.
If you went with this then portals would not work, thus destroying my fantasy with all your physics.
So, unscientifically( or just not discovered yet), I prefer to think that all objects entering and exiting portals keep only their velocity relative to it's planet. So if an object is at rest on earth its velocity relative to earth is 0. Then on mars when it exits, it would end up with a velocity that's 0 relative to mars.[/QUOTE]
I think I haven't communicated my position well enough. I would think that if you did the Earth-to-Mars experiment, and just walked through the portal on Earth, you would calmly walk out of the other side on Mars without suddenly gaining a huge velocity relative to the exit portal. That seems to be the interpretation that makes the most sense in a relativistic universe, and hence that would lead to outcome B of the original scenario being true.
I've made a large amount of progress on getting the GUI for my program at work up and functional. The "SVG" viewer works now, which lets a user view the individual layers of a print and what the toolpaths generated look at this layer. It still needs some work though, as getting the paths to draw in a "fit-to-window" kind of fashion is surprisingly complex and is making me go back and review some of my linear/matrix algebra stuff:
[t]http://i.imgur.com/xEJeFRv.png[/t]
The icons I added are currently missing, along with the fancy and pretty skin ([URL="http://i.imgur.com/hOapgKM.png"]link[/URL]). I've been unable to get the compiled resource package file working, and its not exactly a high priority right now. it took me long enough to figure out [URL="https://truth2.wordpress.com/2010/09/04/custom-build-rules-for-qt-under-visual-studio-2010/"]how to get the Qt Meta-Object compiler working[/URL] in a non-Qt project on VS2017 (no Qt extension yet afaik), and I still can't get incremental builds working so my build time has gone up pretty considerably due to that. The OpenGL viewer isn't ready yet either, as quaternions are giving me a hard time and an arcball camera is really the only option. It also took me a considerable amount of time to get Qt to play nice with context generation and acquisition, since it kept trying to generate an OpenGL 1.3 context (ewwwww) no matter how much I told it otherwise.
At the least, this should make debugging a lot of the profile and toolpath generation SO MUCH EASIER [I]holy shit[/I]. Previously I just exported HTML "SVG" files for each layer and part in a layer (each "island" of material is a seperate part), so on some large objects at high resolution I had thousands of HTML files to try to look through. I usually just ran through and sampled a few, but I realized this wasn't ideal at all for debugging. Using this slider + GUI window is so much easier, as I can pretty quickly spot errors. Like in the above image, something is causing the slicer that turns the 3D model into 2D profiles to decide to amputate part of this poor octopods legs D:
Here's a video showing some of the new stuff I added latelty, mainly an adaptive HDR pipeline, grass rendering, and volumetric clouds viewed from above.
[video=youtube;_Z_DLSnKi9E]http://www.youtube.com/watch?v=_Z_DLSnKi9E[/video]
Look at what you made me do, Unity
All I wanted to do was remove generic components from generic objects and look at what you made me do
[url]https://hastebin.com/jagefuqoze.cs[/url]
Since I was banned in November, I made these:
[b][url="http://youtubecontroller.com"]YouTubeController.com[/url][/b]
For people who watch youtube on their TVs by connecting an old laptop via HDMI cord. It send commands through websockets and you can send videos/playlist and control it using the "remote" section
[b][url="http://github.com/collinoswalt/books"]Books[/url][/b]
For reading text files page-by-page. Saves bookmarks and you can use custom sizes for your reader
[b][url="http://campustips.net"]CampusTips.net[/url][/b]
Submit local tips about your college campus
[b][url="http://barbcomstock.com"]BarbComstock.com[/url][/b]
Nothing really. I just redirected my local republican representatives name to donations for planned parenthood
[b][url="http://collinoswalt.com/woof/new.php"]Woof[/url][/b]
Just figure it out yourself I suppose
Also some other stuff and I got a job and it's great :toot:
[QUOTE=proboardslol;52154484]
[b][url="http://campustips.net"]CampusTips.net[/url][/b]
Submit local tips about your college campus[/QUOTE]
I dig this one. I could see it being useful as a mobile app.
Getting notifications when the Jimmy Johns guy is handing out free samples would be killer.
Plus, college campuses, inevitably have some legends that would be cool to read about.
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What are you working on? v67 - March 2017
