Breaking relativity? Well, it IS wikipedia, but just to make sure...

[questionposter]

http://en.wikipedia....ster-than-light

 

"If a laser is swept across a distant object, the spot of laser light can easily be made to move across the object at a speed greater than c."

citation:

• Gibbs, Philip (1997). Is Faster-Than-Light Travel or Communication Possible?. University of California, Riverside. Retrieved 20 August 2008

<br class="Apple-interchange-newline">

 

I don't get this... light can travel faster than light?

Edited April 21, 2012 by questionposter

[HuMoDz]

The laser dot isn't a physical object or particle. The laser pointer constantly shoots electromagnetic waves at the red dot. You aren't seeing a laser particle, but a "line" of waves that goes from the point to the dot, and then reflects to your eye. It's similar to a cartoon the drawn figures are't really moving objects, so they can seem to travel faster than light.

[questionposter]

The laser dot isn't a physical object or particle. The laser pointer constantly shoots electromagnetic waves at the red dot. You aren't seeing a laser particle, but a "line" of waves that goes from the point to the dot, and then reflects to your eye. It's similar to a cartoon the drawn figures are't really moving objects, so they can seem to travel faster than light.

 

I'm not seeing exactly what you mean. Anything that "seems" to travel faster than light from any frame of reference breaks relativity, and this includes light. By red dot, I'm assuming your referring to the end of the laser pointer. If you take a laser pointer and run it across the sky, the light hasn't actually reached those distant galaxies yet, so there can be anything from that frame of reference to actually observe that phenomena.

There is no way to possibly measure that an object has traveled faster than light in any way without breaking relativity.

Edited April 21, 2012 by questionposter

[Sato]

I'm not seeing exactly what you mean. Anything that "seems" to travel faster than light from any frame of reference breaks relativity, and this includes light. By red dot, I'm assuming your referring to the end of the laser pointer. If you take a laser pointer and run it across the sky, the light hasn't actually reached those distant galaxies yet, so there can be anything from that frame of reference to actually observe that phenomena.

There is no way to possibly measure that an object has traveled faster than light in any way without breaking relativity.

Photons aren't actually moving across the object at the speed of light, you're just changing direction of the laser and light is being fired at that new position. For example, imagine you're observing a 100km long object from a relatively large distance, now point your finger at one edge of it and move it to the other edge; you may have moved across the whole object but your finger is indeed not moving 100km per second.

 

 

 

[md65536]

I'm not seeing exactly what you mean. Anything that "seems" to travel faster than light from any frame of reference breaks relativity, and this includes light.

If you shine a laser at one target P and then at another target Q (as well as any in between), there is nothing physical that moves from P to Q. The "laser dot" as a thing at P consists of different photons than the laser dot at Q.

 

No, not anything that seems to travel faster than light breaks relativity.

http://en.wikipedia....non-information

Typically it will break relativity only if it is possible to send information faster than light, and there is no way by shining a laser at P and then at Q, that you can transfer information from P's location to Q's. Any observer who observes the dot at P and then at Q, even if the two events are nearly simultaneous, will still make these observations subject to the speed of light (the laser hitting P, and light from that being observed remotely, etc, all involve information travelling with v <= c).

Edited April 21, 2012 by md65536

[swansont]

If you shine a laser at one target P and then at another target Q (as well as any in between), there is nothing physical that moves from P to Q. The "laser dot" as a thing at P consists of different photons than the laser dot at Q.

 

And the dots are not causally related, which is when the limitation of c applies.

[Vastor]

this should explained well:

 

[questionposter]

No, not anything that seems to travel faster than light breaks relativity.

http://en.wikipedia....non-information

Typically it will break relativity only if it is possible to send information faster than light, and there is no way by shining a laser at P and then at Q, that you can transfer information from P's location to Q's. Any observer who observes the dot at P and then at Q, even if the two events are nearly simultaneous, will still make these observations subject to the speed of light (the laser hitting P, and light from that being observed remotely, etc, all involve information travelling with v <= c).

 

To my knowledge you can't transmit "real" information, or information comprised of real values of matter and energy, faster than light, and quantum mechanics is no exception. Quantum mechanics with entanglement does not transmit information between two objects because entangled particles are the same object, and delocalization is the mathematical probability of observing information, not the path that information itself takes. If you measure a point appearing at a second place faster than light could get there, the point didn't actually take a path to get there.

this should explained well:

 

 

Individual photons would be measured in separate points or would be observed by individual mechanisms which can't tell each other they saw a photon faster than light , but nothing is actually traveling faster than light, so what's the point? Your not actually observing something going faster than light. So I guess perhaps the same photon isn't actually taking a physical path to get to those various points, but I still don't see how an observer on the moon themselves would actually measure a photon covering more distance than it could traveling at 186,000 miles per second.

Edited April 21, 2012 by questionposter

[mindless]

Modern relativity maintains that if objects of any type follow a minimum length path in four dimensional space-time (called a null geodesic) then anyone observing the velocity of the objects will get the same valuefor the velocity no matter how fast they are moving. This constant velocity is numerically equal to the "speed of light in a vacuum". The moving laser points do not follow this path and relativity is entirely unaffected by such experiments.

 

A corollary of relativity is that faster than light travel by single massive objects would require a re-write of relativity.

 

See http://en.wikibooks.org/wiki/Special_Relativity/Faster_than_light_signals,_causality_and_Special_Relativity