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Location: UFOUpDatesList.Com > 2007 > Aug > Aug 27

Re: 'We Have Broken Speed Of Light'

From: Gerald O'Connell <gac.nul>
Date: Mon, 27 Aug 2007 16:13:44 +0100
Archived: Mon, 27 Aug 2007 14:43:33 -0400
Subject: Re: 'We Have Broken Speed Of Light'


>From: Martin Shough <parcellular.nul>
>To: <ufoupdates.nul>
>Date: Fri, 24 Aug 2007 16:44:38 +0100
>Subject: Re: 'We Have Broken Speed Of Light'

>>From: Gerald O'Connell <gac.nul>
>>To: ufoupdates.nul
>>Date: Thu, 23 Aug 2007 12:52:32 +0100
>>Subject: Re: 'We Have Broken Speed Of Light'

<snip>

>>Anyway, it would be nice to hear on this from List-members who
>>have a sophisticated understanding of frontier physics.

>It would indeed. In the meantime here is my understanding.

You are too modest Martin. After all, in the land of the blind
the one-eyed man is about as sophisticated as it gets!

>As
>someone else noted, this is not a new issue and has been
>vigorously discussed for more than a decade. The consensus is
>that the quantum tunnelling implies no violation of special
>relativity. This is because a photon is not a bullet but a
>probabilistic wave packet and because there are several
>different dispersion velocities associated with photon
>propagation, and it depends which one you are measuring.

>First, classically speaking there is no constraint in SR that
>the phase velocity of a wave has to be subluminal; in fact, the
>phase velocity is generally superluminal and tends to infinity.
>Also the group velocity of a packet of waves can exceed c. What
>may not exceed c is what is called the front velocity. This may
>sound strange, but the distinctions start to come into play when
>you are tunnelling very long wavelength photons over a small
>distance, as is the case with Nimtz (and others, going back
>certainly to 1993).

>A group velocity greater than c is sometimes claimed to violate
>SR because we normally associate the group velocity with the
>signal velocity, which is the speed of information carried by
>the wave. But this is true only in cases of normal dispersion.
>The group velocity can be described as the speed of the envelope
>of the wave packet, and you can simulate what happens in cases
>of abnormal dispersion (such as negative refractive index) by
>combining a couple of simple waveforms (could be water ripples)
>so that by the principle of superposition they generate a third,
>different waveform which has a new velocity quite different from
>either of its parent waves. This velocity can be made
>arbitrarily large or even made to propagate in the opposite
>direction. It's a bit like looking at the racing wagon wheels in
>a western movie and seeing the spokes slow down and rotate
>backwards. Some effects like this have been known for decades,
>such as the apparently anomalous >c group velocity of light in
>some thin metal foils.

>In the Nimtz experiments this is the sort of effect that is
>thought to happen, but it's complicated because it's a quantum
>mechanical tunnelling through a potential barrier rather than a
>classical wave propagation. In such a case the question of what
>happens if you put a barrier in the way of a photon is already
>answered - there is a barrier, and the photon is already
>potentially on both sides of it. This again is a perfectly
>conventional QM effect that has been known for many decades and
>is also a related wave phenomenon that works as well for
>electrons or any particle. In this case the wavefunction of an
>electron in a box (walls = potential barrier) is found to extend
>into regions where for a classical particle the kinetic energy
>is negative and it cannot go, i.e. outside the box, but the
>quantum particle has a small probability of being there,
>proportional to the amplitude of its wave, and sometimes is.

>By reference to the questions of wave velocity mentioned above
>you can see that the question of "how fast does it go?" might be
>complicated, and it is. The wavefunction represents a
>probability of measuring some potentiality which, in some sense,
>is already there. The question of where the electron/photon is
>"really" before we measure it is regarded as a non-question as
>it presumes knowledge of a state which is forbidden by the
>uncertainty principle. Some aspect of the photon/elecrtron
>exists on both sides of the barrier; but the measurable aspect,
>the one associated with signalling information - the
>"translation of a particle" in the case of the electron -
> happens here and then there, sequentially, and this particle
>velocity is alwayts less than c.

>Similarly, in the tunnelling-photons case the probability wave
>plays the part of the classical wave. Some phase components of
>the wave can "travel faster then c" when you arrange things so
>that the pulse width of your wave packet is large compared to
>the tunnelling interval, because parts of the wave are quantum-
>mechanically speaking actually on both sides of the barrier. But
>the bit that contains signalling information is not the phase or
>the group but the wave _front_, and this front velocity is
>approximately equivalent to the group velocity only in this
>special case.

>As far as I can see, if you extend the barrier to be a spacetime
>interval of any practical length then you find that you need
>wavelengths proportionately long to see tunnelling, and the
>quantity of information tends to zero. Tunnelling photons
>between stars for example does have a certain tiny probability
>amplitude associated with it, but for any meaningful probability
>of seeing it happen you need photon wavelengths of lightyears,
>comparable to the thickness of the ptential barrier, which means
>because of Planck's e = h-nu relation that they only contain
>incredibly small energies.

>Anyway the debate has been going on for about 15 years and
>that's is the state of play as I understand it. There are lots
>of web resources.  There's a very useful partial listing by
>Markus Possel updated as of 2001 that contains numerous
>references, a few from his page are quoted below.

>Martin Shough

>Aichmann, H., G. Nimtz and H. Spieker: "Photonische
>Tunnelzeiten: sunb-- und superluminales Tunneln" in
>Verhandlungen der Deutschen Physikalischen Gesellschaft 7, 1995,
>S. 1258.

>I'm listing this brief publication (a conference abstract)
>despite its being in German as it is the only publication
>directly referring to the tunneling of the Mozart symphony that
>I know of. The following article has much more content:

>Nimtz, G. and W. Heitmann: "Superluminal Photonic Tunneling and
>Quantum Electronics" in Progress in Quantum Electronics 21(2)
>(1997), S. 81-108.

>Contains an expose of Nimtz' interpretation of his and other
>tunneling experiments.

>Chiao, R.Y. Chiao and A.M. Steinberg: "Tunneling Times and
>Superluminality" in Progress in Optics XXXVII (1997), S. 345-
>405.

>Good summary of the "conventional" view why there is no faster-
>than-light information transfer in these tunneling experiments.

>Mitchell, M.W. and R.Y. Chiao: "Causality and negative group
>delays in a simple bandpass amplifier" in American Journal of
>Physics 66(1) (1998), S. 14-19.

>Describes a very simple setup with the help of which one can
>understand how faster-than-light (or even negative) group and
>"signal"-velocities can occur without any violation of causality
>and without any faster-than-light information transfer.

>Diener, G.: "Superluminal group velocities and information
>transfer" in Physics Letters A223 (1996), S. 327-331.

>General article about the pulse reshaping which, in the
>conventional interpretation, explains the faster-than-light (or
>negative) group velocities.

Sincere thanks for this post Martin. Immensely helpful.

Digging into some of this material has re-awakened a personal
nightmare for me (the ontology of wave theory is either
crackers, or - more likely - sends me crackers, or possibly
both) - but that's my problem and nobody else's.

I'd recommend List members with an interest in this stuff to
follow up on Martin's good advice, and also the link he
provided:

http://www.aei.mpg.de/~mpoessel/Physik/FTL/tunnelingftl.html

in a subsequent addendum.

I also found to be clear and useful Raymond Y. Chiao: 'Tunneling
Times and Superluminality: a Tutorial' which is at:

http://tinyurl.com/yr2cue


Gerald O'Connell




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