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Thread: " Scientists Make Radio Waves Travel Faster Than Light

  1. #1 " Scientists Make Radio Waves Travel Faster Than Light  
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    I'm still looking for a technical explanation of this.

    http://current.com/items/90301786_sc...n-light/25.htm

    but feel free to discuss.


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  3. #2  
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    Did you read this reply?

    Typical shoddy reporting of technology. The "scientist" is confusing group velocity with phase velocity. Phase veleocity is often faster than light, but contans no informatin or energy. It is common in waveguide structures. While he's built a shiney machine and got a small town paper to go "gee whiz", he's done nothing that radar and communication engineers don't do on a regular basis.


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    I heard about a process that uses quantum tunneling to cause a signal to be sent through a medium in which the pulse reaches the detector at something like 1.7 times the speed of light, and I've read even higher. They still say that the information is not traveling faster than light. But they have also played some Mozart through the devise and the song reaches the detectors at faster than light. So I don't know what they mean by "Information", but if a usable thing like a song travels though the tunneling medium then isn't that proof of FTL communication?
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  5. #4  
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    Quote Originally Posted by Wildstar
    I heard about a process that uses quantum tunneling to cause a signal to be sent through a medium in which the pulse reaches the detector at something like 1.7 times the speed of light, and I've read even higher. They still say that the information is not traveling faster than light. But they have also played some Mozart through the devise and the song reaches the detectors at faster than light. So I don't know what they mean by "Information", but if a usable thing like a song travels though the tunneling medium then isn't that proof of FTL communication?
    You need to supply a reference.

    To my knowledge there has been no transmission of information, nor is any possible using this phenomenal, which is known as quantum entanglement.

    Without a reference, and some research into it, I flat do no believe that they played Mozart or anything else showing transmission of informatin at superluminal speeds. If they had it would be world-shaking news, way beyond typical Nobel prize stuff.
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    same as in a similar post revealing 'amazing new discoveries' I highly doubt it's authenticity purely based on the fact this is the first we (well I at least) have heard of it, it we had broken the lightspeed barrier for something like this I suspect it would be on the news and all sorts



    That said FTL is nothing new, tachyons in particular and many other things are belived, and in some cases are proved to move faster than light

    E=mc˛ (energy = mass X speed of light squared) works for matter, stuff with mass, essentially as the mass gets faster it gets bigger, requiring more energy to maintain the constant speed, thus making it theoretically impossible for matter to travel faster than light
    and although I'm not sure, I think radiowaves can escape this, wave particle duality means Electromagnetic Waves can have no mass, enabling them to move faster than light (of course dr rocket or someone is probably going to come and spout big words at me and call me wrong as usual)
    It's not how many questions you ask, but the answers you get - Booms

    This is the Acadamy of Science! we don't need to 'prove' anything!
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  7. #6  
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    It uses a quantum tunneling effect. Here's an article
    http://en.wikipedia.org/wiki/G%C3%BCnter_Nimtz
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  8. #7  
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    Quote Originally Posted by Wildstar
    It uses a quantum tunneling effect. Here's an article
    http://en.wikipedia.org/wiki/G%C3%BCnter_Nimtz
    Here is the important reference in the Wiki article debunking the claimed superluminal transmission speeds.

    http://arxiv.org/ftp/arxiv/papers/0709/0709.2736.pdf
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  9. #8  
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    The critical error in Nimtz's experiment is in his taking the path traversed by the central peak for the plane wave's propagation as the path of the "photons". The gaussian distribution across the face of the wavefront represents the uncertainty in the position of each photon.

    Now these photons hit his apparatus at an oblique angle and we find that some of them tunnel across the gap. By virtue of tunnelling we then have an updated correlation with their lateral position in the direction parallel to the wavefront. They are not predominantly coming from the center of the transmitting antenna but rather off to the side. The distance they travel and thus the speed calculation (in so far as it can be defined given the uncertainty principle) is wrong.

    This is what comes from confusing the probability amplitude distribution (wave function) with the actual physical photon.

    Lets see if I can give an analogy....
    (In what follows it will be useful to have a picture of Gunter Nimtz's prism experiment at hand. Let A = T and B = R )
    EDIT: Here's my own diagram:


    Imagine a runner leaves a strip of road laying in a north-east direction and the runner is traveling southeast. You are not quite sure from what part of the road he left but you have a probability distribution in the shape of a bell curve with center at point A. The runner if he keeps going straight will come to another highway running north and south. Now imagine that along this barrier road cars are traveling so the runner either gets hit by a car or misses all the cars and keeps on going south east.

    Now you also observe a peculiar statistical phenomenon in collecting data on many runners. Whereas the line the runner most likely takes before crossing the road passes through the point A the line the runner most likely takes given he makes it across lies a bit east of point A. This is to say there is a correlation between how far east of A the runner started and how likely it is he crossed the road. (If you want to be more humane you can assume the runner always bounces off the car and is dazed but unhurt so that he starts running SW instead of SE)

    Now assume that given the runner crosses the barrier highway he will reach another strip of road lying also in a north-east direction. Noting that the probability distribution for crossing runners will be shifted but still a bell shaped curve lets say the center of this bell curve at the second NE road is at point B.

    All the while the runner takes a straight line path and travels at a fixed speed we will call c.

    But you mistakenly try to calculate this speed by measuring the distance from point A to the point (A') on the left side of the barrier highway directly SE of pt A, then you measure the distance from point B to the point (B') on the right side of the barrier directly NW of point B. You then add the distance between these two points A' and B' noting that the slope is a bit shallower than the 45degrees of the lines A to A' and the line B to B'.

    You incorrectly assume the runner traveled along line A to A' then A' to B' then B' to B. You further assume that while running from A to A' and running B' to B he maintains his measured speed of c. You then incorrectly calculate the speed he traveled while crossing the highway. You in fact may find this speed to be infinite.

    The error is in taking the center of the probability as an actual position. Given the runner did start from point A he will not have taken the path B' to B but rather will be traveling parallel but west of this line. (He also is slightly less likely to have even made it across the road compared to the runner who starts east of A and ends up on the line B' to B.).

    Now this exposition does not get into the details of quantum tunneling and why the center of probability shifts during a tunneling event. For that you'll have to get more deeply into the quantum mechanics. But it does show how misreading probability distributions as the actual object they describe leads to fantastic mistakes.
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  10. #9  
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    So basically the wave that is supposed to be going faster is propagating through the barrier without resistance and the second beam has a drag effect so that it takes longer?
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  11. #10  
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    Quote Originally Posted by Wildstar
    So basically the wave that is supposed to be going faster is propagating through the barrier without resistance and the second beam has a drag effect so that it takes longer?
    No that is not the point. My analogy doesn't get into the question of how the wave propagates through the barrier or drag effects. The point is how one incorrectly identifies the peak of the wave function as the position of the particle and thus traces out a path which appears to be FTL. There is also a problem with working with part of the wave function (the tunneling component) which we may view as a conditional probability amplitude distribution.

    Here's another example. Suppose a secret agent is to be parachuted into a city at night and his task is to leave a bomb where ever he lands and then get as far away from the city as possible. Your task is to find him so you can find out where he placed the bomb. You are going to use statistical analysis to maximize your chances of finding him. You know he will travel at a fixed speed say one meter per second.

    Initially the probability distribution is a bell shaped curve centered over the middle of the city. But almost instantly the probability he is dead center will go to zero. In fact a circle of zero probability will expand from the center at this speed of 1m/s.

    But this means there will be a circular peak probability expanding from the center also and this circle must initially expand at faster than the speed of 1m/s because it must be outside the circle of zero probability.


    This doesn't mean the spy is traveling faster than his max speed but that the point we most expect to find him given he is east of town does.

    Note throughout the mean location of the spy stays centered over the middle of town. This also doesn't mean the spy is not moving. We can't take the motion of the probability representation as the same as the motion of the spy.
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  12. #11  
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    Before starting to speculate I sent an email to the person whose name was mentioned in the article and Dr. John Singleton kindly replied me. This is an extract from his e-mail, I hope it helps:

    "Thanks for your email. We do not in fact make radio waves travel faster
    than the speed of light in a vacuum; sorry, but that is not possible in
    free space.

    I am afraid that we do not break any laws of physics. The point about our
    machine (which obeys Maxwell's equations and Special Relativity) is that
    the source of radiation inside it travels faster than the speed of light
    in a vacuum. In other words, it travels faster than the radio waves that
    it emits. The same effect is well known in acoustics; a jet plane that is
    supersonic travels faster than the sound wave that it emits. One of the
    resulting phenomena is well known - the sonic boom. This occurs because
    sound waves emitted at different times in the plane's history turn up
    simultaneously at a particular point.

    The phenomenon is known as temporal focusing (focusing in the time
    domain); it is only possible for sources that travel faster than their
    emitted waves
    (and in fact accelerate). Our source does the same thing for
    electromagnetic radiation, producing a "radio boom". This has many
    potential applications.

    As you can see, the postings on Connect and Digg were full of mistakes;
    although I was quoted, the author of the article had not really digested
    what we are doing and made a lot of what was in the article up.
    "

    We happy?
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  13. #12  
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Wildstar
    It uses a quantum tunneling effect. Here's an article
    http://en.wikipedia.org/wiki/G%C3%BCnter_Nimtz
    Here is the important reference in the Wiki article debunking the claimed superluminal transmission speeds.

    http://arxiv.org/ftp/arxiv/papers/0709/0709.2736.pdf
    He sums everything up on the last page. Of his points, this is the only one that really impresses me as refuting the findings, and so I just want to make sure I'm understanding it right.

    Quote Originally Posted by The Article
    3) Nothing was observed to be traveling faster than light. The measured delay is the
    lifetime of stored energy leaking out of both sides of the barrier. The equality of
    transmission and reflection delays is what one expects for energy leaking out of
    both sides of a symmetric barrier.
    Basically, all of the energy from the incident beam of light converts into an evanescent wave in the gap between the two prisms, and when this wave collapses, it creates both the reflected beam of light, and the transmitted beam of light? He has a really good picture of this on page 10 of the article.

    In a sense, that means the reflected light is really being reflected from the center of the gap, not the edge of the prism, doesn't it? And if the point the light is reflected from is really the center of the gap, then the reflected beam is traversing that gap every bit as much as the transmitted beam.
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