Faster than light phenomenon

I have heard of an experiment involving a Quartz crystal, where light is supposed to tunnel through the crystal faster than c. First of all what is meant by tunneling ? And does anyone know how this crystal is able to accelerate light ? Is there any reverse refraction during the experiment ?

Just asking these questions because when I first heard of this effect, I thought the crystal may be something less than a vacuum, for the light to be able to travel faster through it than in free space.

where did you hear about this it sounds like a fake to me.

Quantum tunneling is when a particles goes through a potential barrier it should not go through. Like having a ball go through the side of a bucket. With very small things the probability distribution of it being anywhere inside the potential well (bucket) is given by wave functions depending on the energy level of the particle. The probability distribution has a non-zero value near the edges of the bucket, so there is a chance that the particle can exist outside the potential well. Those are the particles detected as tunneling though the potential barrier.

[edit on 10-12-2005 by Mxyztos]

Electric signals can be transmitted at least four times faster than the speed of light using only basic equipment that would be found in virtually any college science department.

Scientists have sent light signals at faster-than-light speeds over the distances of a few metres for the last two decades - but only with the aid of complicated, expensive equipment. Now physicists at Middle Tennessee State University have broken that speed limit over distances of nearly 120 metres, using off-the-shelf equipment costing just $500.

www.newscientist.com...

One central tenet of special relativity theory is that light speed is the greatest speed at which energy, information, signals etc. can be transmitted. In many physics-related internet newsgroups, claims have appeared that recent tunneling experiments show this assumption to be wrong, and that information can indeed be transmitted by speeds faster than that of light - the most prominent example of "information" being a Mozart symphony, having been transmitted with 4.7 times the speed of light.

So, has special relativity been disproved, now that FTL speeds have been measured? The first problem with this naive conclusion is that, while in special relativity neither information nor energy are allowed to be transmitted faster than light, but that certain velocities in connection with the phenomena of wave transmission may well excede light speed. For instance, the phase velocity of a wave or the group velocity of a wave packet are not in principle restricted below light speed. The speed connected with wave phenomena that, according to special relativity, must never exceed light speed, is the front velocity of the wave or wave packet, which roughly can be seen as the speed of the first little stirring that tells an observer "Hey, there's a wave coming".

www.aei-potsdam.mpg.de...

Originally posted by siddharthsma
First of all what is meant by tunneling ?

Tunneling is when anything (usually electrons, but ions & photons can be tunnelled) goes through some sort of quantum barrier that would ordinarily forbid this. It is perfectly legitimate science and is the physical basis for the famous Scanning Tunneling Microscopes used to image nanoscale objects. In theory, anything can tunnel, but if you do the math, only really really small stuff has any reasonable chance to tunnel. If it's much bigger than an atom, fat chance.

And does anyone know how this crystal is able to accelerate light ?

Sorry, no idea. As a guess, they might be manipulating the index of refraction so that it is less than 1. (which has been done for a few materials) This could be done by manipulating the frequency of the light, since index of refraction is a function of frequency of the wave coming in.

Is there any reverse refraction during the experiment ?

Not sure what you mean, here. If you are asking whether all the light is transmitted, or whether some is reflected back towards the source, then it is quite likely that not all the light is transmitted through the crystal.

Interestingly, even though it is physically possible to send waves at faster than the speed of light, you cannot send any information at faster than c, and this can be proven mathematically, and experiments so far agree with this.

and this can be proven mathematically, and experiments so far agree with this.

With all due respect "they" tried to say the same thing about the speed of sound... I still think we don't know jack about the universe and in my mind anything is still possible IMO.

Hell Mathmeticians and Physists even said the same thing about the 100 MPH barrier back in the 19th century...

[edit on 10-12-2005 by sardion2000]

Hehe sardion, ok how about I say this:

As far as we know, and based on our limited understanding of the science involved, information cannot travel at faster than c.

Do you know what group velocity is? It would help to look into this.

I'm not sure who Frosty was referring that question to, but the difference between Group and Phase velocity is rather important:

en.wikipedia.org...

en.wikipedia.org...

Originally posted by DragonsDemesne
I'm not sure who Frosty was referring that question to, but the difference between Group and Phase velocity is rather important:

en.wikipedia.org...

en.wikipedia.org...

It was a general reference. There have been some experiments performed which suggest using lasers passing through certain atoms can produce a 'group velocity' about 300 times faster than light.

Originally posted by sardion2000

and this can be proven mathematically, and experiments so far agree with this.

With all due respect "they" tried to say the same thing about the speed of sound... I still think we don't know jack about the universe and in my mind anything is still possible IMO.

Hell Mathmeticians and Physists even said the same thing about the 100 MPH barrier back in the 19th century...

[edit on 10-12-2005 by sardion2000]

So now you want to ignore Special Relativity?

[edit on 10-12-2005 by Frosty]

So now you want to ignore Special Relativity?

Not at all, I just don't take it as the gospel truth. I reconize that in order for unification to take place some parts of Relativity(or QM or BOTH) are gonna have to go or at least be modified.

It was a general reference. There have been some experiments performed which suggest using lasers passing through certain atoms can produce a 'group velocity' about 300 times faster than light.

I though they have achieve far greater speeds using lasers?

[edit on 10-12-2005 by sardion2000]

Originally posted by sardion2000
Not at all, I just don't take it as the gospel truth. I reconize that in order for unification to take place some parts of Relativity(or QM or BOTH) are gonna have to go or at least be modified.

It is the gospel of fact for many people. This is where Einstein states that the speed of light in a vacuum is a constant anywhere in the universe. So, yes you would have to ignore SR.

It is the gospel of fact for many people.

It may be but there are still some experiments left to be done before its completely validated. Just keep an open mind mmkay? Speculation is harmless.

[edit on 10-12-2005 by sardion2000]

An interesting subject

....intriguing I never knew about the crystal technique for increasing velocity of C... Much reading for me thank you..

A similar post here from some time ago.... however read on its worth it some good posts by some on C and speed etc..

Thread ATSNN

However did you know that I can actually transmit information faster than the speed of light just by wrapping a letter around a stone and throwing it at a close recipient?

no im not mad but as already pointed out by another poster its all relative lol...

Dr. Hau, with Dr. Steve E. Harris of Stanford University and two of Dr. Hau's Harvard students, reported the results of their experiment in which a beam of laser light was slowed to the astonishingly low speed of 38 miles an hour. (By comparison, light in a vacuum travels about 186,000 miles per second.) Dr. Hau's laboratory at the Rowland Institute for Science in Cambridge (where she conducts research with the help of her graduate and post-doctoral students from Harvard) ) is one of a handful of organizations studying the interactions of lasers with a very peculiar kind of matter called a Bose-Einstein condensate. It was by shining precisely tuned lasers on such a condensate, or cloud, of ultra-cold sodium atoms that Dr. Hau and her team reduced the speed of a light beam to a pace slower than her bicycle.

From Nature Magazine.

Go on read this one too if only for the fun element... and you will see what I mean.

Thread

MischeviouslyCrestingTheEventHorizon

Regards

Elf




[edit on 10-12-2005 by MischeviousElf]

I love this topic. I know nothing at all about it, but I love it none-the-less.

One of the things that I think causes a lot of confusion and misunderstanding is what we really mean when we say things like, “communication took place at FTL speed” (thus passing along information), or “particle p traversed the distance between point A and point B at FTL speed”.

I think when most of us consider the subject of FTL phenomena, we think in terms of an “object” traveling faster than light. If that’s true, then in order for us to discuss the subject and all be on the same page, we must first agree on what an “object” is, and whether or not phenomena such as shadows or spots from a light beam are to be included as “objects”, since they can indeed change position more quickly than light can travel the same distance. So, what are the requirements for being an “object”? What qualifying properties must an “object” have? Must it carry information? Or charge? Or energy? Must it be physical?

Another thing that should be made clear is that Einstein, although he receives all the credit for it, never stated that you cannot travel faster than light. That is an incorrect inference that became popular, but cannot in fact be derived from any of Einstein’s postulates on the subject of relativity. In Relativity there is no such thing as absolute velocity. Velocity only has meaning in a relative sense from a given frame of reference, and the speed of light in a vacuum applies only within the medium of space. No one knows how fast space itself can travel, or if it even has a limit.

So, I guess if we’re talking about the possibility of going from point A to point B and getting there before a photon of light, also starting at point A and travelling through the "vacuum" of space, then the verdict is still out and there are many avenues yet to explore. Neither Relativity nor Quantum Theory absolutely rules it out, as far as I know, and a lot of smart folks are feverishly working on a solution as we speak.

In my vast and unbounded ignorance, I’d like to think the solution will one day arrive. I’ve got this totally baseless, romantic notion that if something is within the limits of our human imagination, no matter how farfetched, then most likely it’s within the realm of possibility, as well.



[edit on 12/10/2005 by netbound]

[edit on 12/10/2005 by netbound]

I read that a German scientist successfully transmited information at somewhere near four times C.
I'm no scientist but information probably has no mass and therefore the event would not violate the universal speed limit. I seem to recall the 'apparent' observation of what appeared to be superluminous gas clouds either by Hubble or Chandra. But I'm just a redneck and couldn't say one way or the other. We'uns in the South don't be a gettin much edjumacation like smart peoples in them school thingies.
skep

Here’s one for you. I read it somewhere a long time ago, and it illustrates a good point. You can try this one at home

Find a clear space, stand there and then spin around in a circle. Not too fast; maybe 1 revolution every 2 seconds. At the same time imagine the moon is out on the horizon. Now the question is, “How fast is the Moon spinning around your head?” Assuming the Moon to be around 385,000 km away, simple math would bring you to conclude that it’s spinning around your head at 1.21 million km/s, or over 4 times the speed of light. I know it sounds really lame to say the Moon is spinning around your head, when you’re the one doing the spinning, but according to general relativity all coordinate systems are equally valid; even revolving ones.

The catch is, in general relativity you can’t directly compare velocities of objects in different places. The velocity of one object compared to another only has meaning when the other object is within it’s own local inertial frame.

The point being, in general relativity the concept of velocity isn’t very useful and even makes it difficult to define what is meant by “faster than light”. For that matter, from the standpoint of general relativity, to say that “the speed of light is constant” is itself open to interpretation. Einstein himself even said that statement could not claim unlimited validity. He said that without an absolute definition of distance and time, it was unclear how speed would be determined. It’s through modern interpretation and our definition of standard units of time and distance as related to the speed of light that we draw any conclusions regarding it’s constance.

For a better explanation than I can offer, go to math.ucr.edu...

At any rate, all I’m doing is clouding up an already cloudy matter. I look forward to reading what others have to say as the posts continue. Even though the subject thoroughly confuses me, I still find it fascinating …


[edit on 12/10/2005 by netbound]

"Interestingly, even though it is physically possible to send waves at faster than the speed of light, you cannot send any information at faster than c, and this can be proven mathematically, and experiments so far agree with this."

I would encourage looking up a quantum term called "nonlocality."

Edited for a typo, it's a curse.

[edit on 10-12-2005 by FEMA]

I thought of something, tell me what you think.

You know light travels a bit slower in air, because its magnetic field is resisted right ?

Light travels at c in a vacuum, in the crystal it travels faster than c.

This suggests light speed depends on the medium through which light is travelling right ?

Now the reason I asked about refraction taking place in the crystal is, if it did, it would suggest that the crystal in one way is less than nothing ! or that a vacuum is something ! rather than our idea that it is nothing. Because it means that the vacuum is resisting the magnetic field of light, surely, the vacuum must have something in it that resists the magnetic field.

The following is from my textbook "Optics" 4th edition by Eugene Hecht (which has the added bonus of being something I need to know for my final on Thursday, hehe)

...blah blah... some math derivations... we can arrive at an expression for n as a function of w, which is known as a dispersion equation:

n^2 = 1 + [(Nq^2)/(E*m)]*[1/(wo^2 - w^2)]

(gotta love trying to put formulas into a forum, lol)

n = index of refraction
q = elementary charge = 1.6*10^-19 C
E = permittivity of free space = 8.85*10^-12 F/m
m = mass of an electron
N = number of electrons in the volume being looked at
wo = resonant frequency
w = frequency of EM wave coming in (i.e. the light wave)

So at frequencies above resonance, (when w>wo) then the right hand side of the equation is going to be 1 + (something negative) = something smaller than 1.

You know light travels a bit slower in air, because its magnetic field is resisted right ?

Actually, light travels faster in air than in almost anything else. For vacuum, index of refraction n=1 and in air its 1.0000something close to 1.

Another formula:

v = 1/sqrt(e*u)

v=velocity of light wave
sqrt = square root of
e = permittivity of the material (in free space = 8.854*10^-12 F/m)
u = permeability of the material (in free space = 4*pi*10^-7 H/m)

In some magnetic materials, u is much much bigger so the speed of an EM wave going through it is much slower.

Light travels at c in a vacuum, in the crystal it travels faster than c.

This suggests light speed depends on the medium through which light is travelling right ?

You bet it does, exactly right.

Now the reason I asked about refraction taking place in the crystal is, if it did, it would suggest that the crystal in one way is less than nothing ! or that a vacuum is something ! rather than our idea that it is nothing. Because it means that the vacuum is resisting the magnetic field of light, surely, the vacuum must have something in it that resists the magnetic field.

This is an interesting thought! I'm not sure what the answer is to that one. It'll probably take someone better versed in physics than I am to answer it. *points to frosty and/or sardion, who seem to have physics degrees*