Can photons move faster than the speed of light? You wouldn’t think so, not if the name ‘Einstein’ has resonance, but Günter Nimtz and Alfons Stahlhofen (University of Koblenz) have been working on so-called quantum tunneling, joining two glass prisms and feeding microwave light into them. Tunneling occurs when a particle jumps an apparently uncrossable gap, and that’s just what the team’s microwave photons appear to have done, at least a few of them, when the prisms were separated. The bulk of the microwaves were reflected by the first prism.
New Scientist will soon be reporting on this story, which picks up on the German researchers’ recent paper. The tunneling photons seem to have reached the detector at the same time that their non-tunneling cousins did, suggesting movement far beyond the speed of light. The tunneling time evidently did not change when the prisms were pulled further apart.
Is this a violaton of relativity? Perhaps not. Note this from the New Scientist story, discussing Aephraim Steinberg’s views on the matter as an expert in quantum optics at the University of Toronto:
Steinberg explains Nimtz and Stahlhofen’s observations by way of analogy with a 20-car bullet train departing Chicago for New York. The stopwatch starts when the centre of the train leaves the station, but the train leaves cars behind at each stop. So when the train arrives in New York, now comprising only two cars, its centre has moved ahead, although the train itself hasn’t exceeded its reported speed.
“If you’re standing at the two stations, looking at your watch, it seems to you these people have broken the speed limit,” Steinberg says. “They’ve got there faster than they should have, but it just happens that the only ones you see arrive are in the front car. So they had that head start, but they were never travelling especially fast.”
The paper (short, dense and containing a diagram of the experimental set-up) is Nimtz and Stalhofen, “Macroscopic violation of special relativity,” available online. I’ll post a link to the New Scientist story as soon as it goes online. In the interim, here’s the Telegraph‘s brief coverage.
Addendum: The New Scientist story is here, though only available in its entirety to subscribers.
Here in Germany this “Nimtz story” is known since 6 or 7 years because of a docu film in the german tv station br alpha. But this story is controversial because of the distinction of group velocity and phase velocity: a light wave can travel faster than c but not the information on the wave (see jackson, electrodynamics).
Has anyone found out anything more about the FTL”wave ” at Los Alamos posted at Centauri last week?
Also I heard Krauss on KOA Denver last week on interstellar travel. He changed his tune sort of on one type of warp drive-a warp one would work if a signal to set it up at the destination went out at light speeds-the starship could get there instantaly-of course the energy requirements are unreal or close to it
Dr. Steve Schaefer, Ph.D. Princeton University (Physics), “Calculates if X = 4.3 light-years, then T = 3.6 years. Dozens of stars could be reached in five to six years. In fact, a traveler could even go the Andromeda galaxy (2,000,000 light years) in under 29 years (Ship Time in Years) if a constant acceleration could be maintained.” Also see Dr. Carlos I. Calle, PhD, NASA senior research scientist, below on page.
Dr. Schaefer calculates, “If the total distance is X, then the total travel time T is given by expression
X / 2 = (c2 / g) [cosh (0.5 g T / c) – 1] T = (2 c / g) cosh–1 (1 + 0.5 g X / c2) “
Hi David & Michael
David, the FTL “wave” was FTL only for the average position of the wave, but a wave packet can have a long linear spread – thus the leading edge can exceed the wave group’s average speed by reaching an interface between media before the rest of the wave and outracing it via the change in speed-of-light between the two. Or so it appears in this case.
Michael, that equation looks about right. For long distances the cosh(x) function is approximated to decent accuracy by ln(2x.) The function inside the cosh brackets is “gamma” – the time distortion factor. Gamma increases by 1.033 for every lightyear travelled at 1 gee. Thus a trip to M31 (which is about 2.5 million lightyears away, not the older figure of 2 million) reaches a maximum gamma of about 1.3 million – every 24 seconds in the ship’s reference frame is equivalent to 1 year Earth-time.
Of course relativistic red-shift would turn the Cosmic Microwave Background into an intense gamma-ray source, so no one will be flying to Andromeda at 1 gee – in this Universe at least. Ursula LeGuin’s Nearly As Fast As Light ships, in her Hainish Universe, travel at ultra-high gamma-factors in NAFAL Space avoiding the CMB hazard. They also manage to accelerate at about 25,000 gees without squishing the crew.
stephan,wow i just read the above,very impressive.maybe in quantum tunneling we have the first step toward my favorite two propulsion ideas : traversable worm holes and or warp drive! glad to hear any comment you may have. respectfully your friend george udt109@aol.com
MIT looks at the science of quantum teleportation in the
new SF film Jumper:
http://www.nytimes.com/2008/02/05/science/05mit.html?em&ex=1202533200&en=5afb2da248bde941&ei=5087
The Foundation of Reality: Information or Quantum Mechanics?
The nature of information is the key question for those pondering the laws of physics.
Monday, May 18, 2009
We’ve all come across the mind-blowing weirdness of quantum mechanics; that it makes its predictions in probabilistic rather them deterministic form, that it does not allow unknown states to be copied and that one quantum object can instantly influence another regardless of the distance between them, but not in a way that allows faster-than-light communication.
That’s one helluva a theory and in recent years physicists have discovered an entire class of theories that do the same kind of thing. The question is which one do we choose?
A few can be ruled out because they simplify various computational tasks in implausible ways. But the rest have seemed more or less equivalent. Until now.
Marcin Pawlowski at the University of Gdansk in Poland and a few pals say that the addition of a single additional consideration, quickly and easily separates the non-physical theories from the physical ones.
Full article here:
http://www.technologyreview.com/blog/arxiv/23541/