Portal [Interesting Physics]

[Oni-Paranoia]

Re: Portal [Interesting Physics]

Someone please get this guy a science book.

http://en.wikipedia.org/wiki/Asexuality

I think dorby was referring to this. Any time I hear "asexual" I think of that definition, not the actual asexual definition.

[qqwref]

Re: Portal [Interesting Physics]

I was thinking about Phynx's 3rd question in more detail (that's the one where you have two parallel portals being pushed together) and I realized that it really comes down to the fact that the space between the two portals is basically a tube of variable height which "wraps" from top to bottom. If we imagine drawing that tube over and over again to make an infinitely long one an object can fall through forever, then anything inside it will appear infinity times, each one a certain distance (the distance between the two portals) from the next. So far so obvious.

The thing is that when that distance gets very small the object doesn't have a lot of room. Imagine we're using a 10-cm ball. When the distance is 10 cm, there is just enough space in the tube for the one copy, and in fact the ball will be touching the next and previous versions. So what happens when the distance is decreased to 9 cm? Even though the ball is still falling at high speed, it's being compressed, against copies of itself, to 90% of its original diameter. Remember, though, that it takes a certain amount of force to compress objects - if it didn't, you could create elastic potential energy for free, which seems like it shouldn't be allowed even under Portal physics - and this force has to come from somewhere. It's certainly not coming from the portals, since they're just big openings. To me, it makes the most sense to say that this force has to come from the person pushing the two portals together. That is, in this ball example, it will require the same amount of force to push the two boards with portals together, as to push two regular boards together. To go from 10 cm to 9 cm, you still have to provide enough force to compress the ball, and to keep it at 9 cm you need enough force to keep the ball compressed. So, about the 0 cm idea, it's not as easy as just putting the portals next to each other - there is a very strong elastic force preventing you from doing so, the same as it would be to bring two normal boards together with something between them. You would never be able to put the two portals to a distance of exactly 0 cm because of the stuff between them (which has to go somewhere after all) but if you input enough compressive force you could get very close.


tl;dr: Pushing two portals together, with a falling object in between, will eventually result in compressing the object. It should require as much force to do this as it would take to compress the object between two flat surfaces. Pushing those portals to a distance of 0 would require a huge force, and would end up with the same result as doing it with boards: lots of tiny pieces of the object trying their best to escape from the area being compressed.

[Reincarnate]

Re: Portal [Interesting Physics]

Ahh good point

[Sephiroth28]

Re: Portal [Interesting Physics]

I like qqwref's explanation. It makes sense. At least when I read it it does

[Reincarnate]

Re: Portal [Interesting Physics]

technically speaking, perpetual motion machines would be possible (free energy) with portal technology to begin with

[qqwref]

Re: Portal [Interesting Physics]

Yeah, as soon as you put one on the floor and ceiling you get free energy.

Still, it's fun to imagine that the standard laws of physics are obeyed except when they aren't. I guess you can't get very far without that

[Mans0n]

Re: Portal [Interesting Physics]

Someone please get this guy a science book.

Someone please get this guy a science book. ^^


Since he has no idea what the **** he's talkin bout.

[fido123]

Re: Portal [Interesting Physics]

Definitions of asexual on the Web:

not having or involving sex; "an asexual spore"; "asexual reproduction"
wordnetweb.princeton.edu/perl/webwn
Asexuality (also known as nonsexuality) in its broadest sense, describes lack of sexual attraction, or interest in or desire for sex. Sometimes, it is considered a lack of a sexual orientation. One commonly cited study placed the incidence rate of asexuality at 1%.
en.wikipedia.org/wiki/Asexual
The terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota.
en.wikipedia.org/wiki/Asexual_(fungus)
A person who lacks interest in or desire for sex; Having no distinct sex; Without sexual action; Lacking interest in or desire for sex
en.wiktionary.org/wiki/asexual
asexuality - having no evident sex or sex organs
wordnetweb.princeton.edu/perl/webwn

Yeah, AxZ's definition was correct, and Dorby's post should apply to himself.

Anyway would pushing a table with a portal on it through a portal crash the game?

[leonid]

Re: Portal [Interesting Physics]

[Reincarnate]

Re: Portal [Interesting Physics]

new portal experiment

fire portal against wall

fire portal inside a spaceship

get your twin to step inside the ship, but looking back at the portal towards you so you can see each other at all times.

have the spaceship zoom off into space at some significant fraction of c (for a couple years), turn around, and come back

WHAT HAPPENS

[Reincarnate]

Re: Portal [Interesting Physics]

new portal experiment

stand on a stationary train platform with Portal A-1 on your left and Portal B-1 on your right.

have a friend go inside a train car with Portal A-2 at the back and Portal B-2 at the front.

portal A-1 goes to A-2, portal B-1 goes to B-2.

your friend stands in the middle of the traincar and has a light emitter that fires two beams of light -- one towards B-2 and the other towards A-2. The train is moving at a significant fraction of c.

meanwhile, you stand between A-1 and B-1 with photodetector plates aimed at each portal. If they both detect light at the same time, nothing happens. But if one detects light and the other does not at the same time, you are dropped into a vat of acid.

so as the train speeds by, your friend fires off the light emitter.

WHAT HAPPENS

[darkshark]

Re: Portal [Interesting Physics]

Even more interesting than dilation of time between the twins, would be the dilation of the portals themselves, because not only are they at different points in space, they're also at different points in time in that situation.

Also, if you carry your speed through the portal...you'd come out of the portal at near the speed of light, probably not a good thing if that portal is stationary.

*question 2,
Your ass is getting dropped in acid, if you're moving at a fraction of c in the same direction as one of those light beams, then the forward traveling light beam will reach the portal slower than the one firing towards the rear.

[LongGone]

Re: Portal [Interesting Physics]

technically speaking, perpetual motion machines would be possible (free energy) with portal technology to begin with

Lets just say that its offset by the energy required to sustain the Portals, so its not really "free". Discuss

I was thinking about this. As orange block A gets pushed into blue portal on block B, "itself" (lets call C) appears through A. But as A appears through itself, it also has its own orange portal through it (?). Also, what if portal B was large enough so that C could pass through B?

[Reincarnate]

Re: Portal [Interesting Physics]

LongGone: The energy requirements of the portals have nothing to do with the energy involved in the interactions of physical events occurring between the portals themselves. It's not like portals will die out quicker if we're leveraging events between the portals that result in even larger energy gains. The variables involved between both concepts are not "canonically conjugate."

[LongGone]

Re: Portal [Interesting Physics]

What if the energy to sustain the portal is a function of the mass that travels through it

EDIT: Besides mass, there are thermodynamic consequences of Portals (radiative head, etc.), so it might be a function of that too