Portal [Interesting Physics]

[qqwref]

Re: Portal [Interesting Physics]

But we can't lift ourselves off the ground precisely because the force of pulling ourselves up needs to be counterbalanced. Lifting up on a normal panel you're sitting on won't do anything because your body exerts the same downwards force on that panel to counteract it. But if you lift up on the portal panel, the counterforce is exerted on the ground under your feet, which is somewhere else entirely, and not on the portal panel itself. The only thing pulling or pushing down on the portal panel is gravity, and if you can counteract that you can lift the portal.

I thought more about whether you have to lift your upper body too and it turns out that you don't, because even though to an outside observer it seems to be floating in the air, from your point of view the lower part of your body is supporting the upper part. So you just have to lift the weight of the panel.

[LongGone]

Re: Portal [Interesting Physics]

The thing is, as you "lift" the panel, its like lifting a hula hoop. The hoop "rises higher up" relative to your body, but this means that the boundary of the portals is raised too. If the portal used to divide your waistline, by "lifting" the panel its up to your e.g. chest. That means that there is less of your body above the panel now, and more of your body under the table (which, by physical space constraints means you have to squat, or lift the entire table up. The table is supported in the air by the rigid portal fixed to your body)

Referring back to this, say someone is holding your upper body and panel in air:
O
/|\

___
/\

The moment he releases it, the panel will drop together with your upper body as there is nothing holding up both your body and the panel. The person is free to move your upper body/panel however he wants; the weight perceived by him would probably be the weight of the panel(I think the upper body weight will be supported by your own legs through the portal). There is nothing to stop him from moving your panel+upper body; him moving it will not violate your physical state nor the portal

[Reincarnate]

Re: Portal [Interesting Physics]

Say we tie hard metal bars such that they lock in place your waistline to the underside of the table. According to qqwref, I should be able to tug on the panel and float -- or perhaps keep a constant tug and float up indefinitely. But this doesn't make much sense.

Trying to pull the panel up will also pull the table + rest of the world up, and however much you pull up, that much volume will be displaced below the lower portal -- otherwise nothing can be pulled.

[Reincarnate]

Re: Portal [Interesting Physics]

Back to the twin paradox:

What would happen is that you could sit there and chat with your twin as he's chilling there in the ship. Your clocks are synced and everything. 30 years later, your twin over in the ship says "Hey, I'm about to land now."

But you look around and see no ship in sight. "But you're not here!"

You look back in the portal and see that, through the ship's cockpit, he is indeed back in the station. But you notice that the station's clock is 50 years in the future -- not 30. You won't actually notice the ship landing back in the station for another 20 years even though you see it happening right there through the portal. You can even step through this portal and travel forward in time 20 years, or your twin can step through to your side and travel 20 years back in time.

[leonid]

Re: Portal [Interesting Physics]

Back to the twin paradox:

What would happen is that you could sit there and chat with your twin as he's chilling there in the ship. Your clocks are synced and everything. 30 years later, your twin over in the ship says "Hey, I'm about to land now."

But you look around and see no ship in sight. "But you're not here!"

You look back in the portal and see that, through the ship's cockpit, he is indeed back in the station. But you notice that the station's clock is 50 years in the future -- not 30. You won't actually notice the ship landing back in the station for another 20 years even though you see it happening right there through the portal. You can even step through this portal and travel forward in time 20 years, or your twin can step through to your side and travel 20 years back in time.

mind=blown

[Reincarnate]

Re: Portal [Interesting Physics]

I hope Portal 3 starts to include some serious relativity puzzles. It'd make for some really, really interesting mindbenders.

[qqwref]

Re: Portal [Interesting Physics]

According to qqwref, I should be able to tug on the panel and float -- or perhaps keep a constant tug and float up indefinitely. But this doesn't make much sense.

Doesn't make much sense because it's counterintuitive? Or because you see something wrong with the force argument?

Trying to pull the panel up will also pull the table + rest of the world up

How so? If the portal panel isn't connected to the table (and I'm assuming it isn't because if that was the intent leonid would've just put the top portal on the table), there's no reason lifting the panel would have any effect on the table.

however much you pull up, that much volume will be displaced below the lower portal -- otherwise nothing can be pulled.

What do you mean by volume displaced below the lower portal?

[Izzy]

Re: Portal [Interesting Physics]

This might be relevant or irrelevant, but has there been any evidence of changes in time due to extreme velocity? Like if you put a watch in the large hadron collider and had the same watch as a control, would the two watches be any different at all?

I know it's probably taboo to not believe in this concept, but I just find it really hard to believe and as far as I know there has been no evidence to support that the concept of time is a manipulatable dimension.

[fido123]

Re: Portal [Interesting Physics]

This might be relevant or irrelevant, but has there been any evidence of changes in time due to extreme velocity? Like if you put a watch in the large hadron collider and had the same watch as a control, would the two watches be any different at all?

I know it's probably taboo to not believe in this concept, but I just find it really hard to believe and as far as I know there has been no evidence to support that the concept of time is a manipulatable dimension.

I feel the exact same way. I remember Bill Nye the Science Guy explaining it to me when I was just a little kid and since then I've always wondered if maybe science has it wrong. Space and Time is beyond me, I have assumptions but I don't think much of them considering they're probably wrong.

[darkshark]

Re: Portal [Interesting Physics]

There absolutely is evidence of this. Hell even the satellites that orbit earth have to be programmed to compensate for slight time dilation to stay accurate, and those are only going 10,000-20,000mph

I'm probably rusty on my relativity theory, but the closer you are to achieving the speed of light, the slower time gets. Upon reaching the speed of light (which technically shouldn't even be possible) then time would essentially stop, but only would appear to stop if observed by someone else who was stationary/going the opposite direction. The person who was actually going the speed of light would feel as though time were perfectly normal.

So according to the observer, the watches would get horribly offsync, also works vice versa, the person traveling at lightspeed would see the stationary person's watch as being stopped.

This essentially even gives us the ability to travel hundreds or thousands of lightyears away in a single lifetime given we're able to get close enough to the speed of light.

[Izzy]

Re: Portal [Interesting Physics]

But what if that effect has nothing to do with what we think of as time. What if that happens just because of something like your speed is getting closer and closer to the speed at which the electrons are orbiting the atoms. So once both are going at the speed of light there would be no rate of change and thus things would appear to stop. Although maybe this is what "time" is.

[Reincarnate]

Re: Portal [Interesting Physics]

All you need to know is that the speed of light is constant for all observers in all reference frames -- and from there you deduce all sorts of wacky phenomena that have been experimentally verified.

[darkshark]

Re: Portal [Interesting Physics]

I used to think that time was just something we humans pretty much made up to gauge periods between movements, but the more and more you learn about the physics of time, the less you think it's "made up".

Go look up time dilation on wikipedia or something, really interesting stuff, that will undoubtedly lead to much more in-depth reading material.

[Reincarnate]

Re: Portal [Interesting Physics]

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

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

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

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

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

All worth reading

[Reincarnate]

Re: Portal [Interesting Physics]

I just thought of something curious.

In the game, when we put portals on the ground, things bob back and forth, which means that it still feels gravity through the portal even though it's "facing" the ceiling in both cases.