Something to think about

[bojan]

http://www.scientificamerican.com/blog/post.cfm?id=faster-than-light-electric-currents-2010-06-18&sc=WR_20100622

and here:
http://arxiv.org/abs/0903.0399

I remember one very interesting experiment from my student days (back in late '60-ies): It was a laser, stimulated by moving EM shock wave front produced by discharge in the focus of the paraboloidal-shaped edge of flat plate made of dielectric material (FR-4 epoxy-fibreglass , used for printed circuit boards).
The shock front was moving at the speed of light along the laser tube.. but it could have been moving faster if the angle of the laser tube was smaller (similar to what was described here in this SA article, if I understood the text correctly)... only in that case the laser effect wouldn't be possible.

EDIT: Laser tube was inclined at 45° in relation to the axis of the paraboloidal shape of the plate.
I don't remember if experiment was a success or not at the end (was this laser working or not..).

[DavidU]

Ah yes, FTL's. The application of this theory seems to fit the Pulsars focused beams.
Interesting.

[bartman]

Bojan and Dave,
I know I'm way out my depth here but I'm interested in all things FTL.
From what I can gather is that the experiment(s) has produced - is producing - will have produced a FTL radiation/light source.
The reason I have put those tenses in there is cause I'm wondering :

A) how do you measure it? ( I'm guessing its a theoretical confirmation)

B) if it does work and the radiation goes FTL, then how does the theory of relativity work ( not that I am full bottle on that!). Would the radiation go back in time or forward? See question A .Or does it not have anything to with that?

Just curious......
I'll try and decipher your answer as best I can:thumbsup::rofl::thumbsup::quest ion::rofl::question:
Bartman
Bartman

[bojan]

Bartman,
the radiation does NOT go FTL.
The only thing that does go FTL here is phase velocity of the wave front and this does not carry any information... Only group velocity of the wave caries information, and this one can't be FTL.
So relativity still works.
It is the mathematical trick actually - in reverse, so to speak.. how the shape of the pulse generated by pulsar can be described in mathematical form.

I am sure there are others on this forum that can explain this much better :-)


Also, personally I believe that there was mis-interpretation in the article, related to inverse square law or just inverse law that governs the intensity of the pulsar beam.
Inverse law may be applicable to short distances (close to pulsar) but definitely not at the distances pulsars are located.
The similar thing applies to laser beams and antennas in general: In close range, intensity of the radiated beam follows different rules (sometimes 1/r).. but once the dispersion of the collimated beam starts (usually couple of wavelengths away) we have always the inverse square law (1/r^2).
In case of pulsars, collimation effect may be happening in much wider space around pulsar (compared to wavelengths of the radiation), but I doubt very much that this could be the case at much more than fraction of AU away from pulsar.

[bartman]

Thank you Bojan, some of it made sense:confused2:.


(......lost the knowledge part from here...:{)

So from the above quote; the inverse laws dont work at more than around one AU . Scaled down, as in your quote ( radiated beam), we cant confirm a FTL phase velocity unless the test bed is HUGE..... Am I thinking right there?

I am trying to grasp all of this, so excuse my ignorance, BUT I find this really interesting.

BTW I never 'elized' your 10" Dob!!!!!
Bartman

[bojan]

:rofl: