Magnetic fields travel faster than light?

[Strife]

If this was the case... Why wouldn't they measure things in magnetic year away as apposed to light years? I'm not sure if I saw anywhere in here that said how much faster a \"magnetic unit of time?\" was than light... But find me something on that... Otherwise as far as I'm concerned this is all theory because there is no concrete evidence or testing completed.



I did find this though... This makes a little bit of sense...


http://news.scotsman.com/scitech.cfm?id=16902006

[Foil]

[Re: the clock scenario]As you move away from the clock it will appear to slow down and at the speed of light it will appear stopped. If you could go faster than light, you would see nothing because no more information will reach you. It will not appear to be going backwards.

It's true that if you are travelling faster than light, no information/light from the clock will reach you. However, you will be catching up to and passing information/light which has already passed you.

Without worrying about which direction you're looking (just think of the observer as a multi-directional optical sensor if you have to), it follows that the observer is seeing the hands of the clock moving backward.

Follow the logic, and the observer will eventually see something before it happens. This is a contradiction of the principle of causality (cause & effect), so we have to reject the assumption at the beginning of the scenario about travelling faster than light.

[TIGERassault]

Follow the logic, and the observer will eventually see something before it happens. This is a contradiction of the principle of causality (cause & effect), so we have to reject the assumption at the beginning of the scenario about travelling faster than light.

And again, it's not. You still have this weird notion that something only happens when you see it happening!

This is what happens when you put a constant time into it. Let's say a clock strikes 2:00, and this clock is correct. Then, you keep running backwards faster than light. When you stop half an hour later (2:30), let's say that you see the clock striking 1:00. Obviously, one hour later you can see the clock striking 2 again. However, the clock itself actually struck 2 half an hour ago!

[Krom]

In other words: if you travel in a straight line from a clock at double the speed of light for 30 minutes by your watch, then turn around and look at the clock again, you will be seeing light that was reflected or emitted from the clock one hour ago so the clock will appear to be 1 hour late. However if you instantly teleported back to the clock at infinite speed, your watch and the clock would still be in perfect sync. Meaning regardless of how fast you travel, the same amount of time passes for you and everywhere else. Simply because light has a non infinite speed it will only show you things that have already happened, and can never ever show you something that has not yet happened. The apparent compression/expansion/halting/reversal of time from traveling near/at/above the speed of light is just that, apparent not real, merely an extreme example of the Doppler effect.

I never could wrap my mind around the lightspeed = time travel theory, it just doesn't seem right. But there isn't anything better out there so for now we are stuck with it, even if it doesn't make any sense.

[Testiculese]

Clocks run slower the faster you go, so your watch would not be in sync. The Air Force demonstrated this in the 60's.

[Bet51987]

Ok, I see what you guys are doing. In the science fiction sense then yes, the clocks would appear to run counterclockwise. In fact its possible to keep going and watch early man, the birth of our planet, etc.

Krom.. The clocks won't be the same, in fact twice the speed of light for 30 minutes would make the clocks millions of years out of sync.

When you stand still, all of your motion is through time, which is moving at 186000 mps. As soon as you start walking, you are diverting some of your motion through time, to motion through space and since motion through time and motion through space must equal the speed of light, time for you has to slow down relative to the the stationary clock.

Just walking from one room to another, changes your wristwatch and the clock on your wall. They never could test this until the atomic clocks came along because for us, the change is unmeasurable.

Bee

[Foil]

This is what happens when you put a constant time into it. Let's say a clock strikes 2:00, and this clock is correct. Then, you keep running backwards faster than light. When you stop half an hour later (2:30), let's say that you see the clock striking 1:00. Obviously, one hour later you can see the clock striking 2 again. However, the clock itself actually struck 2 half an hour ago!

I understand the logic of your argument, but the bolded phrase is the assumption where it goes wrong.

The thing which seems so strange about special relativity, but which is the fundamental truth we're talking about is: space-time is relative (time is all related to one's frame of reference, so time/"now" is not the same everywhere). It seems completely counter-intuitive, but it's a direct consequence of special relativity, which has been verified over and over and over.

Here is a good article (take your time going through it, I had to) about why faster-than-light travel breaks causality: Relativity, FTL, and causality

[TIGERassault]

Here is a good article (take your time going through it, I had to) about why faster-than-light travel breaks causality: Relativity, FTL, and causality

Ah, NOW you're explaining things!
I understand the article, and Special Relativity fine. But what I don't understand is Lorentz Transformation. (you wouldn't happen to have an article on that, would you?)
Also, it doesn't seem to include what happens when the thing being sent has a space-time distortion of its own!

[Foil]

I understand the article, and Special Relativity fine. But what I don't understand is Lorentz Transformation. (you wouldn't happen to have an article on that, would you?)

Sorry, I don't know of anything handy on Lorentz Transformations (besides the overly-technical Wiki).

Also, it doesn't seem to include what happens when the thing being sent has a space-time distortion of its own!

Ah, good catch. The article presents it as simply as possible (to make the graphs most readable), by using an example with signals which transmit & arrive simultaneously in the same inertial frame ("ansibles", to use the sci-fi term).

The same causality contradiction can occur with non-instant faster-than-light signals, although trying to graph it out visually (the same way the article treats spacetime diagrams) gets complicated, because you have to consider the inertial frames for the signals as well.


Another way I think of it is that the "light cone" formed by the speed-of-light rays from a point P in spacetime defines a sort of "envelope of causality" where things within the envelope can be influenced (cause/effect) by an event at P. If something travels faster-than-light from point P, it can get outside that "envelope of causality", so cause & effect breaks down. (If that didn't make sense, ignore it, and go back to the article. )

[Foil]

...since motion through time and motion through space must equal the speed of light...

Yes. It's not quite as simple as "[motion through time] + [motion through space] = [speed of light]", there's some seriously tough mathematics involved (which I've mostly forgotten since I took the relativistics course), but that's a good way to visualize it.

[Samuel Dravis]

This is how I understand it. At no time does the speed of any wave exceed c, but it can look as if it does if you're only looking at the EM burst effect and not at the star making it.



I seem to have gotten the spiral arms pointed the wrong way. Pretend it's otherwise.