Somebody run this past me.

[ComradeAsh]

http://img14.imageshack.us/img14/1295/1236608016990.png

I don't know a damn thing about this sort of physics, you guys explain it to me.

[Mantikore]

i dont know anything about all this fancy pants light speed physics, but i would guess that relative velocity can go over the speed of light, since it is just relative. :confused:

using basic physics,
Relative Velo of Rocket 2 to Rocket 1 = Velo of Rocket 2 - Velo of Rocket 1.

the magnitude of the speed would equal |Velo of Rocket 1| + |Velo of Rocket 2|?

[Valheru]

^^^ No, that would still imply that the combined speed exceeds c (the speed of light).

Newtonian physics doesn't work for this scenario. General relativity is what you use to explain the answer, which is that the combined speed is c.

Doesn't make sense? Yeah, it's fucking weird, aint it?

An emergent result of the theory of general relativity is that TIME slows down the faster you travel. You also become heavier (you gain more energy, and thus more relativistic mass).

So what's happening here is that, relative from each rocket, time would slow down for each perspective so that the combined speed remains c.

That is, if both rockets are inside each other's event horizon (meaning that you could make a relativistic observation about the other rocket, from one rocket).

It's weird shit but it makes sense if you discard classical physics.


Oh, and this is mah first post. Howdy peeps!

[ComradeAsh]

Well cheers!

Your name seems familiar, and I don't think its just Feist.

[Valheru]

Maybe somebody uses the nick on another forum. Who knows? :D

[scovegner]

Here's an even more funky theory ... time is a dimension. We are moving through it at the speed of light. Since we cannot go faster than the speed of light, and since time is inversely proportional to speed, we cannot go faster than the speed of light because that would be moving backwards in time, and vice versa ..
However we can go slower than the speed of light, which is why time travel into the future is possible if you can accelerate something to a high enough speed ..
Taking this theory further:
s=vt
displacement=velocity*time
Take that we are moving through our normal spatial dimensions at the speed of light ..
let's say we want to move 10m forward ..
10=3*10^8 *time
time=10/3*10^8
time=0.000000033s or 33 nanoseconds
now take that 0.000000033s and feed that into our original formula with the speed of light as our speed through time .. this should give us how far we've travelled through the dimension of time.
displacement=velocity*time
displacement=3*10^8*0.000000033
displacement=10m
So at the speed of light through spatial dimensions time is the same as distance, 1.

What about a more realistic speed? Let's say you're cruising at 220ms-1 (500mph) in a jet plane .. lets say we want to move 2m forward.
displacement=velocity*time
2=220*time
time=2/220
=0.009090909s
Feed that through your time dimension ..
displacement=velocity*time
displacement=3*10^8*0.009090909
displacement=2727272m

So while in the spatial dimension you have traveled 2m in the time dimension you have traveled 272.7km :D




think about it

[Valheru]

That doesn't work quite that way. Time would slow down, which means that relativistically you'd have moved MUCH further than 272km in "true space", but because time has slowed down for you, you experience the speed as being the same as the non-relativist speed.

It's fucking weird.

[Mathematics]

http://img14.imageshack.us/img14/1295/1236608016990.png

I don't know a damn thing about this sort of physics, you guys explain it to me.

The special relativistic addition of velocities formula gives you the speed of rocket 1 in the reference frame of rocket 2, or the other way around. In your stationary reference frame you would see both rockets travelleling towards each other at 0.99c.

[rabbit boy]

Yeah, the addition of velocities at relativistic speeds isn't the same as 2 + 2 = 4 additions.

Don't forget Lorentz contractions -- as you approach the speed of light, the area in front of you appears to squash down so that you travel through it more quickly. Thus, you can actually get somewhere as quickly as you want if you have enough energy. The catch is that when you come to a stop, you'll see that your friends back home (and everything else) have aged a lot more than you have.

Funny thing is, until you stop, it looks like they are aging more slowly than you are, due to the inertial frame of reference you're in. In relativity, at a constant velocity it acts like you are not moving at all and everything else is moving past you. So everything else is moving really fast in your inertial frame and therefore aging more slowly. When you change to a different inertial frame by stopping (relative to the rest of the universe), it causes a shift in perceived ages. The further away the things are from you, the more they are affected. Thus, you get to see the current time as everyone else sees it.

I had to work out that problem a while back. It's a kind of confusing subject.

[LiquidIce]

It's a bit counterintuitive but once you just imagine hitting warp speed you'll get it :D. Time slows, things get elongated and gain mass 'n shit.

[Mathematics]

Don't forget Lorentz contractions -- as you approach the speed of light, the area in front of you appears to squash down so that you travel through it more quickly. Thus, you can actually get somewhere as quickly as you want if you have enough energy. The catch is that when you come to a stop, you'll see that your friends back home (and everything else) have aged a lot more than you have.

Funny thing is, until you stop, it looks like they are aging more slowly than you are, due to the inertial frame of reference you're in. In relativity, at a constant velocity it acts like you are not moving at all and everything else is moving past you. So everything else is moving really fast in your inertial frame and therefore aging more slowly. When you change to a different inertial frame by stopping (relative to the rest of the universe), it causes a shift in perceived ages. The further away the things are from you, the more they are affected. Thus, you get to see the current time as everyone else sees it.

I'm not sure if this is strictly true, you can't say stopping relative to the rest of the universe. What causes the asymmetry in the twin paradox is the change of inertial frames, but any change of velocity breaks the symmetry between the two reference frames. This occurs when the rocket accelerates, or changes direction and speed i.e. when it turns round and accelerates back towards earth.

Until then observers on earth are just as justified in saying that the rocket is moving away from them as the observer on the rocket is justified in saying that the earth is moving away from his stationary frame at close to c! (Ignoring the initial acceleration of the rocket away from the earth).

This is obviously suprising as observers on earth would, when pointing their telescopes to look through the window of the rocket, see time passing faster for the astronaut onboard than it does on earth. Equally the astronaut would, when looking out the window, observe time passing faster on the earth than it does for him.

[rabbit boy]

I'm not sure if this is strictly true, you can't say stopping relative to the rest of the universe. What causes the asymmetry in the twin paradox is the change of inertial frames, but any change of velocity breaks the symmetry between the two reference frames. This occurs when the rocket accelerates, or changes direction and speed i.e. when it turns round and accelerates back towards earth.

Until then observers on earth are just as justified in saying that the rocket is moving away from them as the observer on the rocket is justified in saying that the earth is moving away from his stationary frame at close to c! (Ignoring the initial acceleration of the rocket away from the earth).

This is obviously suprising as observers on earth would, when pointing their telescopes to look through the window of the rocket, see time passing faster for the astronaut onboard than it does on earth. Equally the astronaut would, when looking out the window, observe time passing faster on the earth than it does for him.

Well, you said what I meant to say. So, OK.