# Once and for all: Has C been exceeded in lab experiments or not? **URL:** \ **Category:** Factual Questions\ **Created:** [May 5, 2003, 3:55pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205 "2003-05-05T15:55:41Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [May 6, 2003, 11:06pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/21 "2003-05-06T23:06:59Z")
\*\*Mort Furd \*\*, you may be talking about [this.](http://www.npl.washington.edu/AV/altvw75.html) A [Google search on +nimtz +mozart +ftl](http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&as_qdr=all&q=nimtz+mozart+ftl) returns lots more links about it. It’s definitely controversial but the claim is apparently that Mozart’s 40th Symphony was transmitted at 4.7 c by tunnelling microwaves through a waveguide. IANAP but I would imagine there is some logical explanation that doesn’t involve violating c. ---
**Author:** ![Mort\_Furd](https://avatars.discourse-cdn.com/v4/letter/m/8e8cbc/32.png) [@Mort\_Furd](https://boards.straightdope.com/u/Mort_Furd)\ **Post date:** [May 7, 2003, 7:57am UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/22 "2003-05-07T07:57:06Z")
Yeah, that was it.[Look here for a good explanation.](http://voidspace.hypermart.net/Science/faster_than_light.html) Way down towards the bottom is the story about Nimtz. If you read up on it, you’ll see that it was APPARENTLY at 4.7 times the speed of light. The light got where it was going in almost one fifth of the time it should have taken. If you read the explanation, you’ll see that the light actually only traversed one fifth of the distance. It tunneled through the rest - which takes next to zero time. The light didn’t really travel any faster, it just took a short cut. ---
**Author:** ![Mort\_Furd](https://avatars.discourse-cdn.com/v4/letter/m/8e8cbc/32.png) [@Mort\_Furd](https://boards.straightdope.com/u/Mort_Furd)\ **Post date:** [May 7, 2003, 8:06am UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/23 "2003-05-07T08:06:41Z")
Multiple short cuts, I should say. ---
**Author:** ![mooka](https://avatars.discourse-cdn.com/v4/letter/m/b5a626/32.png) [@mooka](https://boards.straightdope.com/u/mooka)\ **Post date:** [May 7, 2003, 10:41am UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/24 "2003-05-07T10:41:50Z")
Thanks for the link Mort - very interesting! I didn’t understand this bit though: Unfortunately, at this point the universe’s strangely predictable bookkeeping catches up with us again: the signal is carried by the tunneled photons in an “evanescent mode”–essentially the leading edge of a highly elongated photon. Imagine our horse race again, only this time the horses’ noses are rushing out across the finish line, far ahead of their actual bodies. Since evanescent modes carry negative energy and cannot be directly observed until the peak of the photon (or the horse’s center of mass) arrives behind them, their indirectly observable FTL effects once again can’t carry information. Can anyone explain this too me? Does this mean that although the photons did tunnel FTL, we didn’t observe the photons until such a time as light would normally have taken to traverse this distance? ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [May 7, 2003, 11:10am UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/25 "2003-05-07T11:10:32Z")
From [Wikipedia](http://www.wikipedia.org/wiki/Quantum_entanglement) > [@](#): > > Although no information can be transmitted through entanglement alone, it is possible to transmit information using a set of entangled states used in conjunction with a classical information channel. This process is known as quantum teleportation. Despite its name, quantum teleportation can not be used to transmit information faster than light, because a classical information channel is involved. As I understand it (which is only superficially) you could use this effect to send messages at the speed of light which would contain more detailed information of certain kinds than an ordinary modulated laser beam. So you could use QT for interstellar communication of sorts. But no Star Trek dematerialisation, unfortunately. ---
**Author:** ![dylan\_73](https://avatars.discourse-cdn.com/v4/letter/d/ecccb3/32.png) [@dylan\_73](https://boards.straightdope.com/u/dylan_73)\ **Post date:** [May 7, 2003, 11:29am UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/26 "2003-05-07T11:29:05Z")
Ahh…I understand. No new information. Oh well, I guess the invasion will have to be postponed for now… ---
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [May 7, 2003, 11:50am UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/27 "2003-05-07T11:50:19Z")
So, what if it _does_ actually exit before it enters… and you create a chamer thousands of miles long for the experiment… and as the first photon exits, you go “nah, changed my mind” and don’t push the button. Do God and Einstein suddenly appear from a cloud and go “Ha ha fooled you!”? ---
**Author:** ![Mort\_Furd](https://avatars.discourse-cdn.com/v4/letter/m/8e8cbc/32.png) [@Mort\_Furd](https://boards.straightdope.com/u/Mort_Furd)\ **Post date:** [May 7, 2003, 12:05pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/28 "2003-05-07T12:05:21Z")
jjimm: If you were actually exceeding the speed of light, then that could happen. Since nothing actually moves at more than C you will never have the time reversal effect. Think of the chamber as a straight path between two points and the normal path outside of the chamber as as a curved path. The light through the chamber gets there before the light that goes outside of the chamber, but at no time did it actually exceed the speed of light. ---
**Author:** ![Great\_Antibob](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@Great\_Antibob](https://boards.straightdope.com/u/Great_Antibob)\ **Post date:** [May 7, 2003, 3:47pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/29 "2003-05-07T15:47:39Z")
Not to be nitpicky so late in the thread, but the speed of light is always the lower case c. So, ‘c’ is correct, but ‘C’ is not correct. It makes no real difference if everybody understands the notation, but I was initially confused by the subject line’s capital ‘C’. ---
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [May 7, 2003, 3:50pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/30 "2003-05-07T15:50:42Z")
> [@](#): > > \*Originally posted by Mort Furd \* > \*\*Yeah, that was it.[Look here for a good explanation.](http://voidspace.hypermart.net/Science/faster_than_light.html) Way down towards the bottom is the story about Nimtz. > If you read up on it, you’ll see that it was APPARENTLY at 4.7 times the speed of light. The light got where it was going in almost one fifth of the time it should have taken. If you read the explanation, you’ll see that the light actually only traversed one fifth of the distance. It tunneled through the rest - which takes next to zero time. The light didn’t really travel any faster, it just took a short cut. \*\* But, _assuming this is true_ (a BIG assumption), the fact that it tunneled part of the way and therefore took a “shortcut” isn’t really relevant. It still got there before it should have based on the speed limit c. This would allow FTL information transfer which apparently would have all kinds of weird implications for causality. It would allow information to be sent back in time, for example. ---
**Author:** ![Nim](https://avatars.discourse-cdn.com/v4/letter/n/67e7ee/32.png) [@Nim](https://boards.straightdope.com/u/Nim)\ **Post date:** [May 7, 2003, 4:32pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/31 "2003-05-07T16:32:57Z")
If you can’t make a particle have an up or down spin, can you make it more probable that it will have an up or down spin? And then pick the spin that shows up more? ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [May 7, 2003, 5:47pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/32 "2003-05-07T17:47:58Z")
> [@](#): > > \*Originally posted by davidm \* > \*\*But, _assuming this is true_ (a BIG assumption), the fact that it tunneled part of the way and therefore took a “shortcut” isn’t really relevant. It still got there before it should have based on the speed limit c. This would allow FTL information transfer which apparently would have all kinds of weird implications for causality. It would allow information to be sent back in time, for example. \*\* Unfortunately, it’s impossible to even detect it before the rest of the photon catches up (which happens no faster than c): > [@](#): > > Since evanescent modes carry negative energy and **cannot be directly observed until the peak of the photon (or the horse’s center of mass) arrives behind them,** their indirectly observable FTL effects once again can’t carry information. > > Sigh. So, does it really travel faster than light (or does it matter) if we can’t detect it? If a photon falls in the forest … ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 7, 2003, 6:32pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/33 "2003-05-07T18:32:59Z")
> [@](#): > > If you can’t make a particle have an up or down spin, can you make it more probable that it will have an up or down spin? And then pick the spin that shows up more? Yes, you can do things to a particle to make one spin more likely, or even to force that spin. But doing so will break the entanglement. In other words: I can do whatever I want to my electron right here, but I can’t do diddly to **dylan\_73** ’s electron over there on the other side of the Solar System. Unless, of course, I’m willing to wait for a normal speed-of-light communication. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [May 7, 2003, 8:59pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/34 "2003-05-07T20:59:32Z")
> [@](#): > > \*Originally posted by toadspittle \* > \*\*So, does it really travel faster than light (or does it matter) if we can’t detect it? If a photon falls in the forest … \*\* well, considering ALL of the interactions of any given particle in the universe consist of EXCHANGING INFORMATION, then, yes, the photon is said to “not exist” relative to the rest of the universe, until it has been fully transmitted by the rest of the wave. So you can’t really say it is moving faster than c, relative to the observing matter, since you can’t really observe it at all! And velocity without relativity is meaningless anyway. ---
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [May 7, 2003, 10:07pm UTC](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205/35 "2003-05-07T22:07:19Z")
> [@](#): > > \*Originally posted by toadspittle \* > \*\*Unfortunately, it’s impossible to even detect it before the rest of the photon catches up (which happens no faster than c): > > So, does it really travel faster than light (or does it matter) if we can’t detect it? If a photon falls in the forest … \*\* But, the Nimtz experiment is always described as broadcasting Mozart’s 40th symphony at 4.7 times the speed of light. This would seem to imply that you can detect _something_ sooner. From \*\*Mort Furd]'s [link](http://voidspace.hypermart.net/Science/faster_than_light.html): > [@](#): > > Again, this was not a sleight of hand or trick of math: Nimtz actually broadcast Mozart’s 40th symphony across a tabletop waveguide, and reconstructed on the other side an intelligible recording which had tunneled there at 4.7 times the speed of light. > … > Unfortunately, at this point the universe’s strangely predictable bookkeeping catches up with us again: the signal is carried by the tunneled photons in an “evanescent mode” --essentially the leading edge of a highly elongated photon. … Since evanescent modes carry negative energy and cannot be directly observed until the peak of the photon … arrives behind them, their indirectly observable FTL effects once again can’t carry information. This is confusing to me. The first paragraph says that Mozart’s 40th was sent at 4.7 times c AND RECORDED. But the second paragraph says that this phenomenon can’t be used to carry information. Unless you want to argue that Mozart’s 40th is not information or that recording it is not observing, then these 2 paragraphs seem to be contradicting each other. Somethings missing here. Can anyone clear this up for me? [Previous page](https://boards.straightdope.com/t/once-and-for-all-has-c-been-exceeded-in-lab-experiments-or-not/173205.md?page=1)