Light Breaking Speed of Light?

Hi jorrie, I agree, this is breathtaking! I'd like to know how it can be proven though...

Hi PlbMak, Could you please explain to me why light cannot go faster than 186,000 pr second? Also, if it is true that light can exceed the designated speed then it is proof of a fourth dimention! Spencer.

Could you please explain to me why light cannot go faster than 186,000 pr second?

Hi, if my middle name was Einstein I might be able to, but as it isn't, I wont! As to the forth dimension, well; that used to be called time, but I think it's been supplanted.

hi Scapolie,

I'm not PIBmak, but I'll do my best anyway.

Why anything? In the end, not a scientifically answerable question.

But the reason we believe that nothing can pass through c (the speed of light or about 300000 km/sec) is that the arguments that lie behind the best mathematical models (those that fit our measurements as closely as measurement accuracy will allow) indicate this. Mathematically, the equations for light mean it always propagates at exactly c, but interactions with matter can cause the light energy to be successively transferred to later waves. That means that the effective speed of light passing through a medium theoretcially be any value less than c (I say speed because the direction of the re-emitted wave will not in general be the same as the original). So the crucial issue is that the matter cannot be tavelling faster than c. The reason for this is that energy, mass, and momentum equations all include a term 1/sqrt(1-v²/c²) in their formulae - which means that we would need infinite energy available for anything with mass to even reach the speed of light.

Let us consider a set of particles (representing matter) perfectly aligned as a row, equisized and of equal mass, elasticity, density etc.

Now, if an impetus is given at one end (say, the left most particle), and is insufficient to overcome the inertia of the particles, the ENERGY of this impetus will be transmitted progressively to the rightmost particle in the row, however, with a diminished value. Can we agree on this?

If yes, does not the enrgy transmission represent a COMPRESSION part of a "Wave", leaving the particles unmoved and unchanged, except perhaps the rightmost (unsupported or Neighborless) particle which may or may not undergo displacement depending on its inertia being greater or lesser than the "disturbance"?

In this case, the particles (matter) cannot move faster than the Wave's propagation velocity. (Nothing can move faster than light)

If now, we have a very small particle set and the wave is of very high energy, sufficient to overcome inertia of the particles, would they not experience displacement at the speed of the wave?

I don't know what you mean by "overcome the inertia of the particles". Momentum is conserved and transfer is apportioned according to known laws. The idea that inertia is "overcome" is alien to quantifiable physics.

Similarly, as you write it, I still have the impression that you believe you can consider the situation as if energy vanishes; this too is conserved, so if you can't where it went you won't have a workable model of what is happening.

It's not directly relevant to what you write, and only applies to discontinuous situations - but in "slow wave" acoustic media 'particles' can (and sometimes do) move more rapidly than the wave's group velocity. That doesn't apply to free-space light, of course.

I don't really see what you and Physicist? are debating...

Your example is the classic thought experiment, "If I had a rod of steel a light year long, and if I hit one end..." The result of which is that the impulse travels through the steel at the "speed of sound" for that type of steel. The other end of the rod does not move instantaneously.

Also, everyone needs to remember that what makes matter seem solid is NOT a bunch of little particles banging into each other, It's the electromagnetic force!!!

"Also, everyone needs to remember that what makes matter seem solid is NOT a bunch of little particles banging into each other, It's the electromagnetic force!!! "

force!!! : = MASS X ACCELERATION. If elctromegnetics represent "Zero" rest mass, where does the "FORCE" come from?

That's why, I understand it as "little particles banging into each other" and clinging to each other, because of waves continuously passing through these bunches of matter, having rest mass and being accelerated=FORCE of being "Bound" or "Seperated" giving off energy causing further waves in the process.

It is these waves that are being cognised as ENERGY and a variety of physical phenomena known as LIGHT,HEAT,MAGNETISM,SOUND,X-RAYS etc each of which have UNIQUE (ranges of) frequencies and Wavelengths.

Now, now D.RAMAKRISHNA NAIDU. I've already warned you onc about smoking that happy weed.

They may have zero rest mass, but when moving, they actually do have energy and can transmit force. (E/c²) = m.

I don't really understand this. As I see it the article says that photons are being reflected off a prism and detected while others are having to travel an extra 1m to the other prism then reflecting off that and detected. The two sets of photons are reaching the detector at the same time even though one set has travelled further. Sounds a little fishy to me. Why should one set of photons speed up. Is there some strange law which says that these photons should always arrive at their destination at the same time?

Then what happens if you put another set of prisms in line. Do they speed up again? Hell we could make as many prisms as we like and send data through space as fast as we like.

Doesn't add up to my blue collar train of thought but I've maybe miss understood what they are talking about. Please correct me if I've missed the point.

Hi MACA, I think that the article probably confuses the so-called 'tunneling speed' of the photons with the real speed. Tunneling is something like: the particle is supposed to be here, but suddenly (instantaneously) and unpredictably it pops up somewhere else.

The problem is that one cannot send information via the tunneling of a single photon, because you do not know which photon will tunnel or when the tunneling will happen. By the time you have sent enough photons to have a good probability that a tunnelling event will take place, the overall speed of information travel is again below light-speed in vacuum.

Jorrie

Am I right in thinking that the tunnelling phenomenon is random and doesn't happen to a set proportion of photons when subject to this test?

I studied quantum mechanics while doing an Applied Physics degree and I have to say that it confused me in a way no other subject has. I'm not even going to pretend to understand this but never the less it does seem to be quite interesting.

Hi MACA, you asked: "Am I right in thinking that the tunnelling phenomenon is random and doesn't happen to a set proportion of photons when subject to this test?"

I have the idea that with many photons, tunneling happens to a fixed % of photons, but I'm not sure. It's just that it is (probably) probabilistic and you cannot tell in advance to which individual photons it will happen.

Maybe Fyz and Roger can comment on this?

Jorrie

Uh oh...I feel a Heisenberg uncertainty moment coming on...

...nevertheless...

(uh oh,)

Hi Jorrie & Other CR4 physicists,

Correct me if I am wrong but is what they are claiming something along the lines of this:

From what I gather when they have the two prisms as in the lower example they measure the time that it takes for the photons to travel through the distance marked as S1. When they then separate the prisms most of the photons are subject to total internal reflection but a few tunnel through and when they measure the amount of time the photons took to travel through the distance S2 it is the same as the time measured in S1.

I'm getting confused now. I don't think the above diagram works though cos remember the angle of incidence is equal to the angle of reflection with the angle being measured from the line perpendicular to the face. The above diagram shows the photons going straight through the first prism when I think they would head downwards at an angle of 45 degrees.

Also correct me if I'm wrong cos I'm not really picturing this experiment very well in my head.

Sorry MACA I should have added arrows indication the direction the photons are traveling. Here is an updated image.

In the lower example the two prisms are touching each other so there is no total internal reflection taking place and the photons pass through.

In the upper example the two prisms are separated by some distance and so most of the photons entering the first prism are subjected to total internal reflection and shoot off vertically. However, a small number of photons tunnel through and end up appearing at the outer edge of the second prism as if the two prisms were touching each other. The thing they are claiming is that the photons that tunnel through in the upper image take the same time to travel over the distance marked as S2 as the photons in the lower example that travel through the distance S1.

That's what the drawing represents and is how I interpreted the report of the findings, but it may be completely wrong so don't take it as representing what is being discussed until somebody confirms or dismisses it.

Ok I'm starting to see what's going on here and as the picture becomes clearer I get even more confused. I think the problem I'm having is trying to picture the scenario in a classical thought process which often doesn't happen in quantum mechanics.

Thing I don't get why should the placement of the prisms have any effect on the photons? If I put the second prism 1m from the first prism and then got another two prisms and placed them 1km apart are they saying that if you shone photons through the first two prisms then they would emerge at the second two at the same time?

If that's the case then how do the photons "know" there is a second prism waiting for them.

Anyway I have really confused myself on this one. Anyone know of a more detailed article on these guys cos I'd like to know more rather than speculate. Don't need all the maths cos I probably wouldn't follow it anyway but maybe something with a few more details.

Hi, I'm new to CR4 and I'm not an engineer so please forgive any ignorance on my part. I think you're understanding the phenomena better than you believe by acknowledging this steps outside the domain of classical physics and into the quantum realm. A similar experimental result was achieved several years ago by an NEC team working in Princeton, NJ as well as an Italian group working on the same issue. Here's a good link at Science News Online giving some background on the phenomenon: http://www.sciencenews.org/articles/20000610/fob7.asp

If you will forgive my answering your prism question with another question, how do individual photons know where to strike a target in the double-slit experiment to display the classic interference pattern in aggregate? In other words if you shine a light source through a double slit, the target will display the interference pattern between the two slits. Changing that streaming light source to one which can emit individual photons through either slit randomly over time, the cumulative effect will be the exact same interference pattern. How do the individual photons know to strike the target where they do to create that pattern? A little off topic perhaps, but it demonstrates another mystery of light's behavior which makes it such a fascinating subject.

A good posting, Guest! Why don't you get an avatar and join CR 4. It's more fun that way.

Anyway, the photons don't know where to strike the target. Instead, on the way to the target they interact with each other as wave. As waves, peaks and troughs interact to either reinforce each other (brighter) or cancel each other out (dim). I think the point here is even when you treat them as particles, under certain conditions, they maintain their wave nature. Make any sense?

Hi Vermin,

Thanks for your encouraging comment. I see now that had I read a bit further down in the thread, I would have seen the double-slit mystery raised by others. I'm aware of the wave/particle duality of all emitted radiation, so as a constant stream of photons, the "wavyness" of light setting up wave-like interference patterns on the target doesn't surprise me. The surprising thing to me is when an emitter is set up (with various polarizing filters I suppose) to emit discrete photons (exhibiting their "particleness"), they still strike the target cumulatively as though part of one or the other wave; with the same pattern. It's as though - for lack of a better description - they are programmed to accumulate on the target with wave-like behavior despite having been emitted as discrete particle-like quanta.

Blows my mind. BTW, I hope this gets posted with my forum ID as I logged in, but it still says I'm not. I'll try logging in again just before posting this and see what happens. Thanks again.

This is just to test my login again as "Enquiring_Mind". Not sure what I may e doing wrong.

Had to feed the cookie monster. :-)

Personally, I didn't think I had too much of a problem when I thought I could treat wave-particle duality as the (speed-of-light) wave representing a probability distribution. But then came the single-particle theory and experiments, in which it was shown that if you emit a single photon, only a single photon would be detected. End of wave as photon-probability model, unless you allow instantaneous field collapse.
I'm hopeful that higher-dimension mathematical models that show "quantisation-as-turbulence" may eventually yield insights - but whether ordinary mortals like myself will be able fully to appreciate them is a different matter.

Be that as it may, none of the "faster-than-light experiments" to date has shown any evidence of energy or information travelling faster than the speed of light between source and receiver. What they have in common is local group velocities that are faster then the speed of light. To the best of my knowledge, only Gunter Nimtz has claimed "faster-than-light" sets-up where information-velocity measurement would be practical (formerly with the waveguide below cut-off and more recently with the frustrated-internal-reflection system), and he has not so far reported any such results.
In fact, the situation for the waveguide below cut-off is relatively straightforward, as the entire analysis can be performed precisely without resorting to quantum mechanics, and this makes it simple to show that in this case neither energy nor information are propagating beyond the speed of light. Perhaps that is why Dr. Nimtz abandoned that line of enquiry; if so, the fact that he did so without apparently stating that this turned out to be a dead end does not to my mind support his credibility; if not, it places the whole of his (unpublished) theoretical bases under a considerable shadow.

You may believe that I am not maintaining an "open mind" on this; I think this is confusing open-mindedness with credulity. My position is that I will find it woth serious consideration once we have either
. data from an experiment that at least measures actual time delays, or
. theory that actually predicts a photon (or other particle) appearing earlier than the speed of light would predict.
To date, all I have seen is arm-waving explanations that use faster-than-light transmission to explain experimental results that appear fully explicable within the confines of special relativity. Until there is something more substantial, I see that as more akin to conjuring than physics. (Ectoplasm, anyone?)

Fyz

"I don't understand all I know about that" is a quote from Jerry Clower,famous country comedian.The same applies to the double slit experiment.Many variables affect the outcome, including wavelength,distance between the slits, shape of the slits,distance between bands of light and the central maxima,and the distance from the slits to the screen, and a few other variables I probably forget to mention.

I would be curious to see a similar experiment performed with 2 single-fiber optic strands instead of slits.This may just open another can of worms, but then again, it may provide insite on the slit experiment results.

AIW

Hi masu.

I understand the setup exactly as you have shown. AFAIK, tunneling-time is accepted to be shorter than what a photon would normally take to travel the distance ΔS=S2-S1 in vacuum. Nobody knows if a single photon really travel that distance, because if you try and check if it did, you apparently destroy the photon.

As I tried to state before, the photon is supposed to be 'here', say at your top (invisible) detector, but with some probability, it sometimes pops up 'there', say at your left (invisible) detector. This happens at exactly the time that it was supposed to appear at the top detector, despite the fact that the distance to the left detector is larger.

But is it the same photon that you pumped into the setup that ended up there? Partly because you can't answer that, it is apparently impossible to send information that way. The other reason is you do not know which photon will tunnel (or at least trigger a tunneling event), I think.

Fyz and Roger, where are you guys?

Jorrie

Do you have any idea how these guys might have proved their experiment if you don't know if the photon which has tunelled is the one you sent out?

Slightly off the topic but just a thought which popped into my head. What is the fewest number of photons humans can emit from an instrument. Is it possible to send a single photon from some kind of apparatus. How do we measure the number of photons being emitted?

Hi MACA.

The details in the articles are not yet enough to know how they did their measurements, I think.

I know there are ways to emit single photons at a time, but I'm not sure how it works. I'll wait for Roger and/or Fyz to notice that they are needed here!

Jorrie

Hi Jorrie,

I think this phenomenon is somehow related to the double slit phenomenon.

-John

IF it is as interpreted, it's a bit more than that. Photons in the double slit phenomenon will not arrive before they could get there at the speed of light - the instantaneous nature is in the "collapse" and there are lots of sub-C ways to explain this away - although they end up so complex as to be readily shredded by Mr Occam.

I suspect it has more to do with the intrinsic non-linearity of refractive index - the delay through the prism not being quite what first appears.

Sorry, I've seen some more detail - the authors say the prisms are separated by a metre. So this is neither frustrated total reflection nor standard tunnelling. If accurately measured and reported, it would indeed be the first case of communication at greater than the speed of light. I find it hard to believe that this would be quantum entanglement, because the scale and structure of a prism is such that you would expect the necessary correlations to be lost in the time it would take to move separate them be a metre. SFIK, that would leave some entirely new and unpredicted phenomenon.

Until checked and repeated by others, I tend to the view that this is most likely some sort of equipment issue; this could include the use of generation methods that effectively create a pulse that propagate synchronously from the two interfaces. (But I do recognise that there is more in this universe than could possibly be dreamt of in my philosophy...). On the other hand, it is worth being aware that Gunter Nimtz has 'form'...

http://www.sciencenews.org/articles/20000610/fob7.asp
http://arstechnica.com/news.ars/post/20070816-faster-than-the-speed-of-light-no-i-dont-think-so.html

Thanks Fyz, this clarifies the 'state of the issue'.

Meanwhile, I'll stick with my mental picture: some photons are hiding inside those prisms and when the experimenters pump more in on one side, an equal number instantaneously jump out on the other side, just to confuse them...

Jorrie

<continuing post #28 which, oddly enough, follows (Don't ask: I have a 5-year-old tugging at my elbow as I write this )>

Nimitz, et al, writes, "Evanescent modes or photonic tunneling-like tunneling solutions of the Schrödinger equation have a purely imaginary wave number. This means that they do not experience a phase shift in traversing space.

The time delay τ of a wave packet is given by

τ = d φ / d ω (1)

where φ is the phase shift of the mode or of a particle and ω is the angular frequency.

In general, φ is given by the real part of the wave number k times the distance x. In the case of evanescent modes and tunneling solutions the real part of k is zero. In view of Eq. 1 propagation across the barrier appears to take place in zero time. In the case of particle tunneling Eq. 1 is replaced by the corresponding derivative of the S-matrix.

Despite the fact that the semiconductor tunnel or Esaki diode has been used since 1962, the particle barrier penetration time has not yet been determined due to the parasitic time-consuming electronic interaction effects in a semiconductor. Around 1990 the mathematical analogy between the Schrödinger and the Helmholtz equations inspired microwave and optical tunneling experiments to obtain empirical data on the tunneling time. The experiments with evanescent modes revealed superluminal energy and signal velocities.

Several QED and QM calculations predicted that both evanescent modes and tunneling particles appear to propagate in zero time. The only time delay arises as a scattering time at the barrier front, which has been shown to be a universal quantity of the order of magnitude of the time of the inverse center frequency of the tunneling wave packet."

Hi -e, thanks for your inputs.

We have three threads on this one, but no problem - it's important enough.

Am I right that it is not (yet?) possible to send information faster than local 'c'?

If so, is it because the virtual photon that 'does the tunneling' loses the information?

Or has it to do with "The only time delay arises as a scattering time at the barrier front,...", meaning useful information arrives no earlier than what 'c' would require?

Or what?

Jorrie

For the case of frustrated internal reflection,I find it most intuitive to consider this in the domain of "classical" optics, but as modified by the work of Brillouin and Sommerfield. The zero-phase-shift of the evanescent wave relies on the refractive index difference, and the refractive index is generated by non-linear action that involves precursors - so it only becomes meaningful after the precursors have arrived at the relevant interfaces. The fastest precursors travel at the speed of light, so that is the minimum possible time delay before the phase equality can be built up. Obviously, the sums get messy if you try to solve the full set of QM equations, and it is all too easy to make approximations that predict otherwise; however, SFIK, no-one has produced a credible solution that shows information propagating faster than the speed of light.

Equivalent (but even more complex) considerations apply to the case of electron tunnelling. But I can't see any reason to expect a different result.

Fyz

it's the process of quantum tunnelling...

refer this site it gives the clear explanation for ur ques...

both for the 1st diagram and the speed of light more than 'c'

some signals travel 4.7 times faster than light due to the effect of quantum tunnelling.

http://www.absoluteastronomy.com/topics/G%C3%BCnter_Nimtz

What a farce (referring us back to Gunter Nimtz).

A steady-state wave will indeed have fewer wavelengths between the source and the measurement point. However, a wave-front will take at least as long to propagate from the source (to wherever) as it would in free space.

Other than complexity that allows such conjurers to perform their mathematical sleight of hand, frustrated total internal reflection is in principle no different from other interference phenomenon - such as phase velocity in metal waveguides, or (simpler yet) two coherent waves travelling at an angle to each-other.

In all these cases, the wavelength of an established wave is longer than the nominal free-space value. But the wave-front (= energy, information) still travels at (or below) c.

The only case I know where the jury is (partially) out on faster-than-light transmission is quantum entanglement. However, even here the concensus seems to be that, although the entangled particles will make their transitions simultaneously, there is a delay before either particle makes the transition. I.e. you cannot systematically cause the joint transition to occur in less time than it would take light to reach the further particle.

This experiment is functionally little different than quantum tunneling as routinely exhibited by Esaki ("tunnel") diodes and other semiconductor devices, except that the barrier thickness and wavelengths involved in the former case are much larger. It makes little difference, really, whether an electron is tunneling through 20 angstroms of dielectric in the case of the diode, or that a 32.8 mm wavelength microwave photon is tunneling through a 1 m gap, except that in the latter case the tunneling time (effectively zero in both cases) can be easily measured. This is not the result of twinning/entanglement, but a direct result of the Uncertainty Principle. Nor do I agree that this is an equipment issue, as the barrier-thickness-to-wavelength scales are comparable in both cases. The fact that the microwave photons experience zero phase shift regardless of the barrier thickness supports the idea that the photons have, in fact, tunneled to the second prism in zero time.

Now you've clarified the experiment is frustrated total internal reflection (do you really think it is helpful to call that tunnelling?), there's no doubt about the zero phase shift. But SFIK the information delay (whether predicted by QM or by classical wave optics) between the source and the sensor always exceeds the in vacuo propagation time of light. I'm open to convincing if someone shows (using either reproducible experimental evidence or validatable calculations) that the total-path time between source and sensor reduces when the prisms are inserted in the path.

N.B. that I don't call this group delay, because that concept is only valid when the attenuation of the signal is frequency-invariant (remember student discussions about whether anomalous dispersion exceeded the speed of light?)

Fyz

P.S In retrospect I should have said specifically that "zero phase shift" only necessarily implies zero information/energy delay if the amplitude is independent of frequency.

In regard to the double slit experiment:

Since space time is warped by matter and energy, and matter and energy must conform to this warped form, and since space time is in motion,even thru the smallest particles of matter,perhaps the double slits are actually creating a wave effect in space time. Space time has a different "speed"(for want of a better word) thru the plate surrounding the slits than thru the slits themselves.The photons or electrons, etc. are simply following the dictates of space time. Attach two strings, one to each slit, and blow air thru the slits.The strings will wave, and sometimes interfere with each other. A single string, with the proper velocity of air,will stay straight.The strings are analagous to space time.

This could be easily tested by using plate materials of different densities,and by precise machining of the slits, with possible slit form and spacing eliminating the wave pattern.

Just a wild idea, I guess

HTRN

Jorrie,

Here's a diagram of the experiment as it recently appeared in a scientific journal...

Notice they're using microwaves, not visible light. Also, notice the dimensions.

Hi vermin.

Thanks, best pic I've seen on this.

I think Europium and Fyz have explained it around post #27 or thereabouts.

I still do not believe that information went faster than c, because I do not think that any wave front that could carry information ever went faster than c.

Jorrie

I just saw this in a magazine and thought I'd better get it posted because it seemed so different than what everyone was speculating about.

As I replied to MASU, this may not be a matter of moving faster than c, but rather some unknown quantum structure of space/time that allows objects to change their position in space independent of normal ideas of motion in space.

It's nothing of the sort - so far as I can judge, this one just confuses phase and modulation. If it hadn't already been extensively covered, I expect these guys would "discover" that anomalous dispersion could convey information faster than the speed of light (because the "group velocity" often exceeds the free-space speed of light).

Fyz

Interesting detail from the 10-JUN-2000 Science News article regarding thr Italian superluminal team experiment having been devised so that reflected microwaves in open air overlapped and interfered as they sped away from the mirror. It seems that the constructive interference created a moving pulse along the axis of the apparatus whose speed varied according to the configuration of the experiment. The researchers reported in the 22-MAY-2000 Physical Review Letters that within 1.4 meters of the mirror, they clocked such pulses at up to 125 percent of c. Beyond that distance, the effect died out.

I noticed that open air gap in Vermin's diagram of the Nimitz experiment was 1 meter. Sounds to me like Nimitz et al may have been measuring the propogation velocity of an interference pulse rather than the actual microwaves themselves? Is that what you meant by confusing the phase and modulation?

There are some similarities, but the region where Nimtz thinks he observes the overall advance is outside the interaction region.

The following describe two possible interpretations of what Nimtz has presented - I don't know which it is, because there is not enough data.

First, I'll look at linear systems:
As background we can first consider propagation of waves (longer than 10-cm wavelength) on water. You can see waves growing at the back of a group, overtaking the group and falling. The wave velocity is much faster than the propagation velocity. This is an example where you see apparent "faster-than-group-velocity" movement - but the energy travels at the group velocity. This definitely does not correspond to Nimtz's experiment, but demonstrates how easy it is to allow local observations to cause confusion.
Next, consider a wave that has a group velocity that is faster than c, but whose attenuation changes with frequency. That could be what Nimtz and co-workers have; but for this case detailed analysis taking both wave-velocity and attenuation into account would show that the energy/information propagation velocity is less than c. This is equivalent to the majority of cases of what is known as "anomalous dispersion" near the absorption edge of lossy refractive materials.

Now to a more subtle version. Essentially, refraction is actually an apparently linear output from non-linear interactions. Because the refracted wave is not present initially, transients and steady-state behave differently. So it is possible that there are situations where the steady-state solution for the refractive index plus loss gives solutions where energy/information travel faster than c. However, whenever amplitudes change, so do the non-linear parts of the interaction - and this is what determines the rate of energy/information flow.

There is no evidence from Nimtz's publicity to indicate whether he has even performed calculations to eliminate the first. Based on his previous publicity based on cut-off waveguides, he would need to have progressed quite a long way for this to be the case. But I hope I'm being unfair.

Fyz

Dear Vermin

in the diagram,there is a point (let us call it TP for transition point) at the middle of the gap of 1 metre, from where there are two paths; a) continues to Detector on the right and b) diverges at right angles and goes to the Detector at left. Distances from TP to both the Detectors are equal and so there is no wonder that Detector at right receives the signal at the same time (despite gap of 1 metre) as the Detector at left. It does not seem to matter that it has "Tunnelled" or not.

Please correct me if my observations are not ok.

Thanks and regards

D.Ramakrishna Naidu

The prism is just close enough to allow a very small proportion of the radiation to be coupled in the manner known as "frustration". So the reflected radiation (to the left) is almost completely unaffected by the presence of the second prism. So the mid point really is irrelevant.

The feature that the alchemists** are citing is that the phase of the transmitted radiation (to the right) does not change as you move the second prism and the detector to the right - away from the reflector. That is all fine. What is not fine is their implication that this means that the transmission time of the radiation is also independent of the distance you move prism+receptor to the right; the phase is unaltered, but the time for a change in the signal level to reach the right-hand detector does depend on the position of the prism/detector combination.

**I call them alchemists because they are playing in this area of physics in a way that is equivalent to what the alchemists were doing when trying to turn base materials into gold - they could see certain effects***, but did not have the basis to discriminate a proper meaning.
***Actually, this is probably unfair on the alchemists, because at least some of them were careful empiricists, and would have properly checked the for any effect they thought they saw - and as a result they came up with quite a range of useful materials and methods (but not including turning base metals to gold - or transmitting information faster than light).

In the words of Albert Einstein, "Yes and no, liepshen"

Whether these particular guys got it right... I don't know. All I did was to read the article and provide the correct diagram of the experiment. On the other hand, tunneling is a very real thing. The electrical component, the "tunneling diode" works by this process. And, I might add that most of your electronics (including your computer) would never have been built without scientists and engineers acknowledging and using quantum mechanics!

So, you decide for yourself.

What makes you think I am denying the existence of tunnelling? Given that tunnelling is the particulate effect of evanescent waves, it is perfectly valid to regard this effect in that way; however, this is one of those occasions when the wave approach (based on the actual** refractive index of the materials) is sufficient both to predict/explain the measurements and to show why the interpretation is incorrect (so why complicate unnecessarily). Neither am I arguing that "these particular (particulate?) guys" got their measurements wrong - the phase of the wave is precisely as they report. What I am saying is that the interpretation is wrong - and if "these (not-too) particular guys" took the trouble to measure the delay in the signal (=modulation or data) they would see it conformed very closely to the naivest predictions - i.e. it is equal to the path delay taking account of the refractive index of the prisms; alternatively, they would obtain the same result if they were to calculate the same thing - what makes the difference here is the rapid frequency-dependent change in the attenuation of the signal. Given the areas where you delve, this is pretty elementary (pun not intended) stuff; so get off that fence, work it out, and give an opinion.
BTW, I don't recognise the quote - where did you find it? (on which subject, Einstein was no fan of equivocation...)
P.S. The diagram of the experiment is misleading - the vertical part drawn in the reflected path implies a vertical shift of both the reflected and the frustrated (OK, tunnelled if you must) beams. In fact, both beams emanate from their respective prisms at almost precisely the same height that they would reflect of the first prism in the absence of the second.

**Yes, I know you need QED to model that - but we can still use it as input to a quasi-classical model.

Considering it's been what? 10 months since this thread started and has not seen a whole lot of action for awhile, I gotta say, I really can't remember what that simple diagram was supposed to show. One thing is clear, if they're using microwaves, those probably aren't your normal run-of-the-mill prisms.

I really need to go back and see if I can hunt down the original posting in New Scientist, and read it again.

As far as Albert is concerned... He did have a private life, ya know.

Almost certainly a polymer - PMMA? I seem to remember that the New Scientist quoted a wavelength of 33-cm - but (given the sizes of Nimtz's prisms) I think that it is more likely it was 33-mm.

BTW, I've had a look at some of the refutations on the web - curiously, even those that include what I regard as correct material back this up with "explanations" that are (at best) flaky.
Examples of the flaky include:
. the "shortened train" explanation (simply not relevant), and
. "the reflected energy suffers the same delay as the transmitted energy" which is essentially a correct description of the phase but not true of the energy delay.

So what is PMMA?

Also, are you really saying that you weren't satisfied by the answers given by those that criticized the experiment?!

There was another experiment like this that was conducted on a TV show - on the Discovery Channel, I think. Let me know if you want me to draw a diagram... 'cause I got the deluxe 64 color box of Crayons, including copper, silver, and gold; and a handy sharpener on the box!

Q1) Polymerised methyl methacrylate. It is a well-established transparent acrylic polymer commonly known by a number of trade names. (You could of course have entered the string into a search engine...)
Q2) Yes

Please lend the drawing kit out when you are not using it (not to me, I've zero artistic talent)

Why attempt to use a single photon to carry a signal?.Use a packet of photons, only some of which get thru, to signal a one or zero.It would be wasteful, but the packets could be modulated to send info.Even if you lose some bits, with current Error Correction methods, lost bits be can be replaced at the receiving end to complete the info packet.This would be very valuable for transmitting data over long distances, such as to/from robots on Mars or other planets, and perhaps one day real-time communications with explorers in space.

If this experiment by the Germans holds up to scientific scrutiny, it is a landmark.

Hi HTRN.

"Why attempt to use a single photon to carry a signal?.Use a packet of photons, only some of which get thru, to signal a one or zero."

Yea, this may be possible and AFAIK, it has been demonstrated like this (a microwave pulse with a lot of photons). The problem is that it has not been demonstrated that information can be transferred faster than c by this means. It is apparently a group velocity vs phase velocity issue, but I'm not too certain about the details.

Jorrie

The limit to the amount of information that can be carried by a stream of photons is at the very least dependent on the wavelength.

Also, when there were much faster bit-rates, both Pioneer and Voyager both used a 300 baud rate for sending data back to Earth!!! What the heck was up with that, other than a possible savings in energy.

France is working on a way to communicate with satellites using quantum entanglement. If they succeed, they will have created the first secure data link that doesn't need encryption.

One more thing... You are aware that particles don't "really" spin, correct? We use the analogy of spin simply because it's convenient.

Hi vermin.

"One more thing... You are aware that particles don't "really" spin, correct? We use the analogy of spin simply because it's convenient."

I think it was MASU (reply #76) that had a thing about the 'spin' that was a bit dubious, not me.

Yep, I understand that quantum entanglement may be able to give absolutely secure comms, but FTL comms? Not quite.

Jorrie

Jorrie, Hi!

I wasn't really responding to you, but to the whole thread in general. So forgive me if it sounded as if I was bumping you personally.

This quantum entanglement/quantum tunneling thing is a puzzle that has yet to be figured out IMHO. That demonstration of sending Beethoven over the tunneling side of the experiment at 2.25 c was pretty convincing. This is not to say Einstein was wrong, but rather that there may be more to the fabric of space and time on a "Plank-ish" level than we previously understood.

This Dutch guy that's playing around with deterministic properties of energy and matter below the quantum level may actually find properties of matter and energy that eventually become fuzzed out in the quantum fog when finally observed at those levels.

As for the French , I think all they're trying to achieve is something that Uncle Sam can't un-encrypt, even if it travels no faster than the speed of light.

A final thought - This one is very counter-intuitive, but seems to stick to the roof of my brain, like peanut butter... What if you went so far down in the scale of space/time that on some sub-Plank level it becomes impossible to determine your position in space/time - something like exceeding the graininess of a type of film. Would you find yourself potentially popping back out at some random "other place-time" in the Universe. I don't know, but it makes my head hurt!

Hi again vermin.

"That demonstration of sending Beethoven over the tunneling side of the experiment at 2.25 c was pretty convincing."

Nope, I don't agree. They have not shown that the (Mozart, I seem to remember) piece came out sooner than what straight light comms would have done. They made some measurements of a microwave pulse through the 'tunnel' and claimed that it arrived before non-tunneling microwave pulse. Even this is disputed due to lack of details about their test.

Then they pumped a piece of music over the 'tunnel' and said, "see, it was information that went superluminal". Not a convincing test at all - they did not even attempt to show a phase shift between the musical routes, AFAIK...

"Would you find yourself potentially popping back out at some random "other place-time" in the Universe. I don't know, but it makes my head hurt!"

I think you will only pop out one Planck length away, at most, I think. Not worth the headache...

Jorrie

PS: it was MASU's reply #86, not #76 as I referred to before.

Hi Gals & Guys,

Please take anything I ramble on about with a grain of salt. It's not based on any real scientific or realistic background and is really meant to stimulate conversation.

Anyway, I have a fried that is an Associate Professor of Physics at Flinders University specializes in grand unity sort of concepts. He and the PhD students he supervises have come up with some really interesting if no totally bizarre concepts with the level of bizarreness proportional to the quantity of red wine consumed during their brainstorming sessions.

Anyway, he is firmly convinced as am I, that at a fundamental level the universe is very simple and it is just our attempts to describe and analyze it with mathematics and geometry that is too restrictive to explain it.

He is also firmly convinced that someday we will be able to travel to the stars in a realistic and practical time frame, but it wont necessarily mean traveling faster than light. I assume he is talking along the lines of quantum tunneling or something equally bizarre where you move from A to B without passing through anywhere in-between.

I can't say that I am convinced we will ever reach the stars or that another race will visit Earth but in the universe is a really bizarre place and the more we learn about it the more bizarre it seems to become. One can always hope.

I guess all that we can be certain of is that we can never be certain of anything.

Hi masu,

"I assume he is talking along the lines of quantum tunneling or something equally bizarre where you move from A to B without passing through anywhere in-between."

Seems to me that even if one could achieve a way to "tunnel" oneself from A to B, there would be no way to know where B is. A pig in a poke! Go through the tunnel and you may very well come out in the interior of a VERY hot star, or who know what.

However, I do agree that at some level, as yet undiscovered, some of us will find that the universe, in all its wondrous majesty, has a marvelous simplicity to it. By that I mean it will still require mathematics to describe it, but in an elegantly simple way. Perhaps as elegant as Einstein's famous equation E = MC².

-John

This sort of "tunnelling" of electromagnetic radiation is more informatively described as "Frustrated (total) Internal Reflection. It can be modelled using Maxwell's equations and the "classical" materials properties of the prisms. Under certain circumstances, both a "Phase Veloctiy" and a "Group Velocity" for the overall path will be observed that are greater than C, both in the modelling and in practice. So have we got information propagation that is faster than C? Not in the least. The prima facie evidence is that a Maxwell's equation model fits the experimental data. But you will want to understand why the high group velocity does not predict a high rate of modulation transfer.

Let us start with the basic idea that group velocity corresponds to information transfer velocity: it is exact only if both the attenuation and the group velocity are independent of frequency. Whenever either or both attenuation and/or group velocity vary with frequency, the correspondence becomes inexact (i.e. nearly always...). When the changes with frequency are large, the correspondence becomes non-existent. This is the case for the well-known situation of anomalous dispersion near the optical absorption edges of dielectric materials, and has been so extensively modelled and taught that refutation would soon follow.

The only reason that I can imagine that the present work has not already been publicly refuted is that there is not enough published data to tell you that the situation is as I have interpreted it. It remains possible (though unlikely) that Dr. Nimtz has done something different. In my view (given Dr. Nimtz's history), the likelihood is that even if he has done something different it would merely require different technical arguments to refute his apparent claim of faster-than-C transmission of data.

The one thing that does appear clear is that he has not actually measured the delay in the information propagation*, and compared it with what would be achieved using a direct path. That would stimulate a raft of replicate experiments and analyses to verify that the result was not due to experimental error - assuming that sufficient experimental details became available.
*Establishing a couple of nano-seconds on a noisy signal with a maximum frequency of around 20-kHz sounds quite challenging - especially when you recollect that the amplitude will vary rapidly with frequency, and the demodulation system is likely to be sensitive to this - even if the average carrier levels are equal.

Fyz

Here's where things get funky... Every transistor, every laser, every IC is based on quantum physics. Likewise the tunneling diode used with microwave radiation is also based on quantum principles.

Quantum electrodynamics predicts that if you pile a bunch of electrons up on one side of an impenetrable barrier, each electron is going to have its own wave function. Some of the wave functions will (by probability) be larger than the width of the barrier. When this happens, those electron will disappear on one side of the barrier and reappear on the other side. This process happens instantaneously. And the time required to get the signal over to the other side of the barrier is dependent on the electron population that has these long wave equations. Best quantum estimates say that you will get enough electrons piling up on the first side with a wave equation sufficient to move to the other side, such that the signal will move at about 2.25 c to the other side.

It really seems to work, and that's what makes the tunneling diode work. It's friggin' weird, isn't it!!!

Hi vermin, you wrote:

"Best quantum estimates say that you will get enough electrons piling up on the first side with a wave equation sufficient to move to the other side, such that the signal will move at about 2.25 c to the other side."

What's preventing us from sending information (meaning send and detect events, i.e. cause and effect) at faster than c then? Is it the probabilistic nature of the tunneling?

Jorrie

Yes, and a lot of physicists said the same thing, until the guy hooked his Walkman up to the experiment and sent a rather noisy signal of Mozart across the tunneling side.

A lot of physicists are quietly ruminating the experiment, trying to make sense of both the quantum and relativistic ramifications of the whole thing. I don't blame them, it's weird!!!

"... until the guy hooked his Walkman up to the experiment and sent a rather noisy signal of Mozart across the tunneling side."

Yea, but nobody believes that the music went over faster than what a straight light signal would have done - and he has never proved it.

BTW, I think the Mozart piece was not played over the last experiment that he reported on, but at some previous, even less credibly reported effort.

Jorrie

Yes, this is the problem with these sort of experiments... They don't occur in the lab and who knows whether they're repeatable.

This was one of those impromptu experiments shown on the Discovery Channel, and I haven't seen anything about it since!!!

One other thing... I don't think this violates relativity because it's playing in a totally different world than that of space/time as Einstein was working with.

This may be a whole different level of reality - just as Einstein's world was a whole different level of reality compared to Newton.

One other thing... I don't think this violates relativity because it's playing in a totally different world than that of space/time as Einstein was working with.

Pardon my ignorance but what is this world that does not adhere to space/time?

cr3

The Plank level (and possible sub-levels). Here, physicists are just starting to understand the structure of space and time on these levels. The first findings seem to indicate a very different structure of reality, where space and time may behave more like a chaotic foam. Compare this to the difference between the macro world and the world of the subatomic.

Dear Vermin, I'm stopping here to reply for there is a little word twist that serves my work on coming up with a good thought experiment, that I haven't been fully successful in formulating.

You may remember from years ago that I was trying to figure out how might one encode holograms on photons, and the coherence problem was an stumbling block.

Far as I understood that was that the turn to pure energy would wipe out any discrete encodes.

Since then I have expanded my concepts of the Universe way beyond any finite universe to the point of accepting the possibility of universes with faster or slower constants for the speed of light.

The expectation is that no change really would exist between one universe and the other, except for a different constant for the speed of light.

How to use that, as a reality to move matter forwards or backwards in time, should it actually be the case, is an experiment I cannot yet fully formulate, if ever.

Jorrie has actually addressed problems of individual photons and clumps of them I have not either been able yet to fully figure out possible to make work.

Is dark matter leakage?

Can one photon leave the wave?

Is the Universe way bigger than one?

Does Light ever in this universe move faster than the constant common, and if not, if there is another with a faster, or slower constant, is riding so impossible, as to make even thinking of it a waste of time?

Here's an idea derived by string-theory... There are universes parallel to our own, but string theory does not allow our universes to interact (pass photons, for example) except through gravity. Thus, there is some belief that dark matter and dark energy is caused by gravity from a universe that is parallel to our own.

Your response seems entirely orthogonal to my comment. I believe that I've described the situation for frustrated internal reflection (the present report) rather precisely. You may allow the full complication to be apparent by building up the full QM solution - but it won't change the result in this case.

A previous experiment by the same group used electron tunnelling. Here, I don't think you can avoid the use of rather more complicated quantum-defined wave equations. Consider, however, what happens when you construct the relativistic QM model for the process: the waves propagate at c, with contributions due to interactions that produce any observed delays. Interactions can indeed cause instantaneous collapse of the wave over all space - but the wave must already be present in order to collapse. Because all interactions are dependent on the presence of the wave, and themselves propagate at c, there is no way that energy (or information) can propagate from the source to the receiver at a velocity that exceeds c.

Assuming this description to be correct (it fits any manipulations I have done, but that is not a guarantee, of course), Nimtz and company's "funky" behaviour does not represent transfer at greater than c. What "transfer at greater than c" represents is simply misinterpretation of data. Yes, they have information transfer; yes, they have group velocities that are greater than c; no, they have neither energy nor information transfer that exceed c.

I'd be interested in refutations (i.e. support of transmission at > c) that address the points I have made. I shall however regard any further repeat of the claims of Nimtz & co. as being fatuous, unless the claim be supported by theoretical refutation of the above or credible measurements of anomalous delays in information (or energy) transfer.

Sorry to be so blunt - but I think we've had more than enough unsupported speculation here

Regards

Fyz

Hi Fyz.

I agree with your assessment and also do not have much faith in the group that made the claim.

Jorrie

Hi Fyz,

You said "I'd be interested in refutations (i.e. support of transmission at > c)"

John Cramer, a physics professor at the the University of Washington says "Basically you use an ultraviolet laser to produce a high energy photon, and you introduce this into a nonlinear barium borate crystal. For every high energy photon going in you get two photons coming out, each with half the energy. They're momentum-entangled in that the vector momenta of the two outgoing photons have to add up to the momentum of the photon that produced them. So you separate the paths of the two photons and send them in two different directions...

[Now] let us imagine that you send the first photon through a big spool of fiber optics so that it didn't arrive until tomorrow, and you then use that photon to send a signal. If the second photon goes right in to the receiver, you can send messages to yourself from tomorrow."

You can find more about it here.

-John

Hi John, tx for the interesting link: "You can find more about it here."

I see the pdf from that link is dated April, 2007 and it said that the "experiment is still under construction."

I wonder if they found anything or whether the "will perhaps be prevented by the complementary relation that exists between wave coherence at the slits and momentum entanglement of the downconverted photons" won the battle.

Jorrie

Hi Jorrie,

I didn't realize the pdf file was from April.

What I quoted was an excerpt from an article in this months issue of Men's Journal magazine (October 07, page 108). I realize it's not a scientific publication, but that doesn't detract from John Cramer and his work.

Cramer said that in order to delay the photon by an entire day, he estimates he would need about 10 trillion meters of fiber optic cable. Which is why, he goes on to say, for his experiment he's going to try to delay a photon's arrival by only about 50 microseconds.

When asked by the interviewer if he thinks his experiment will work, Cramer said "Most likely not. Nature probably won't allow you to get away with sending information backward in time. But I don't see what the so-called showstopper is going to be, so we're pursuing the experiment. It's a rare opportunity to probe nature at the most fundamental level."

In the article, John Cramer does not indicate the current state of his experiment. I thought you guys would appreciate the info.

-John

Cramer at least is doing serious work that can potentially show up real effects.

What he is investigating is completely different to what Nimtz and co. As I said in an earlier post, quantum entanglement and related effects may present an escape route from the constraints I described, and SFAIK the jury is still out on that.

However, the thought experiment as described seems to present a problem: the first photon to be modulated or detected will cause modulation of its twin - so messages from tomorrow will not be possible - at least not by using the method described in your quotation. But that doesn't necessarily mean that faster-than-light transmission will not be possible using some such scheme - transmit two beams from a point exactly midway between a "transmitter" and a "receiver", and entanglement might give you instantaneous communications at a distance. I haven't thought too hard about issues with selecting the frame of reference, but I suppose it must be the frame in which the entanglement was generated in the first instance.

A final pair of notes:
. I'd be cautious about whether significant lengths of optical fibre will leave the entanglement undisturbed - given that refractive index effects are effectively the aggregate of a large number of interactions with a non-uniform material.
. My purely personal view is that the more likely conclusion will be that quantum entanglement of this nature will not be sufficient to enable faster-than-light transmission of information, but that the explanation could be something even more 'strange' than entanglement itself. That makes the work well worth doing - though I feel it behoves the workers to be more careful about the way they describe the work and its possible consequences than your quote would seem to indicate.

Fyz

Sorry, the waves we're talking about here are not electromagnetic, they're wave-like structures of probability, and are not "necessarily" bound by c. But that's just my fatuous reply.

Further, I am not an apologist of any quantum physicist or their theories. However, while these experimenters have not proven much, at the same time, you don't see lines of physicists queuing up to rip them a new a-hole, either. This would be more the natural behavior of physicists that were certain there was nothing to it. Need I mention the scientific community's reception of cold-fusion?

So-called "faster than light" barrier tunneling experiments were elegantly explained in papers by Winful in 2002: http://sitemaker.umich.edu/herbert.winful/files/winful_origin_of_hartman_effect.pdf.
and
Tunneling time, the Hartman effect, and superluminality: A proposed resolution of an old paradox

It would appear that Nimtz has not fully accepted this explanation. On the other hand, he has yet to publish any results from more recent experiments. I doubt he will be published until he can show time-delay measurements that show the data travels faster then light; the large distances possible with Frustrated Internal Reflection seem to indicate that is his eventual intention, but the articles do not indicate these measurements to have been made as yet.

If he presents time-delay measurements that support his apparent present view, there will be interest, controversy, etc. The work will be repeated (as is relatively straightforward - the main difficulty is the low signal level you can get at delays that are a significant fraction the available inverse bandwidth). If the small delays are confirmed, Nimtz will have achieved something significant; if not, he will be marginalised, but probably not unemployed - see Fleischmann below.
If (as I fully expect) his measurements confirm Winful's analysis**, Nimtz's scientific reputation will not have been significantly harmed - although people will be wary of him as a man who presents his hypotheses before perhaps he should.

**which I paraphrased here in another posting, but without being aware of the original work as it happens

Cold fusion got heavily taken up by the popular press, because of its possible application to clean*** energy. The workers had sensible track records, but made no claims at the time to theoretical expertise in nuclear physics. As I remember it, the scientific reaction ranged from "inexplicable - but must check it out", via "inexplicable - some-one else's problem" to "almost certainly wrong - let someone else check it". At one point, I recollect Fleischmann and Pons reported an issue with temperature drift in a sensor, but I believe they found some of the effect did not appear to be related to that. At least until quite recently, Fleischmann (b. 1927) was still working with various Naval research laboratories.

***Energetic neutrons and palladium - clean??

Meanwhile, I find it hard to cope that you're apparently advancing a view and then claiming not to be an apologist. Presumably that fence you are not-quite-sitting on is too sharp to stay one side or t'other?

Fyz

I am not sitting on any fence, I'm just not as ready as you seem to be to dismiss the whole matter as BS.

What gave you that impression? I said that I'd judge the case when there was either cogent intellectual back-up or measurements of delay. Until such time, the status quo persists; if anyone finds intellectual arguments to support the faster-than-light case I'll look at them seriously, as I have the ones advanced so far - and if I find the arguments as presented unconvincing I shall continue feel at liberty to say so, despite any accusations that I "have a closed mind" on these matters*.

I note that Nimtz's set up (as reported) only requires the use of a sinusoidal signal, a correlation integrator, and a phase detector to establish a provisional delay for the "tunnelling" signal. He would have to be careful to measure the direct signal and the tunnelled signal at similar intensity, and confirm the relationship between amplitude and measurement delay, of course. But this means that, assuming he is serious, we should not have to wait long before some (at least provisional) results emerge.

*BTW, without careful measurement or reasoned argument, BS is precisely what it remains - even though it could possible turn out to be correct.

Fyz

________________________
Some relevant quotes:
From business-school (to be read both ways): "BS does not necessarily mean the premise is wrong - just that the author doesn't (expect you to) understand the arguments"
The second is the way I feel about your accusations of closed-mindedness (it was a piece of advice given during my high-school days) "Do not confuse credulity and open-mindedness. An open mind sorts and evaluates arguments and data; a credulous mind is more like a waste-bin - it's where other people are free to place their intellectual rubbish."

If you prefer a different term, then the "angular momentum" of electrons is the property being exploited for Spintronics Technology.

They have been able to place single electrons on a substrate, and move them around with a specially tuned laser, and change the spin* of the electrons with circular polarized light.They have also discovered that the "spin* reverses when an electron crossses a PN Junction.The technology is currently in it's infancy, but I think it has a fantastic future,especially in quantum computing.

Note: * Angular momentum

It's not really angular momentum, either. If one is going to be a stickler about it, I suppose the most correct thing to say is: "That quantum state that acts something like angular momentum, but it isn't really." We can change this quantum state, and we know that electrons do not like to exist in the same quantum state with a neighbors and will change their quantum states just to be different from their companions.

Of course, we can get a lot out of the spin-model by thinking of this quantum state as spin, just as we can get a lot out of the "little solar system" model that Bohr first postulated for the structure of atoms.