Speed of light broken with basic lab kit

New Scientist.com ^ | 16 September 02 | Charles Choi

[aculeus]

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

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

Jeremy Munday and Bill Robertson made a 120-metre-long cable by alternating six- to eight-metre-long lengths of two different kinds of coaxial cable, each with a different electrical resistance. They hooked this hybrid cable up to two signal generators, one of which broadcast a fast wave, the other a slow one. The waves interfere with each other to produce electric pulses, which can be watched using an oscilloscope.

Any pulse, whether electrical, light or sound, can be imagined as a group of tiny intermingled waves. The energy of this "group pulse" rises and falls over space, with a peak in the middle. The different electrical resistances in the hybrid cable cause the waves in the pulse's rear to reflect off each other, accelerating the pulse's peak forward.

Four billion km/h

By using the oscilloscope to trace the pulse's strength and speed, the researchers confirmed they sent the signal's peak tunnelling through the cable at more than four billion kilometres per hour.

"It really is basement science," Robertson said. The apparatus is so simple that Robertson once assembled the setup from scratch in 40 minutes.

While the peak moves faster than light speed, the total energy of the pulse does not. This means Einstein's relativity is preserved, so do not expect super-fast starships or time machines anytime soon.

Signals also get weaker and more distorted the faster they go, so in theory no useful information can get transmitted at faster-than-light speeds, though Robertson hopes his students and others can now rigorously and cheaply test those ideas.

Physicist Alain Hache at the University of Moncton in Canada adds that it may be possible to use this reflection technique to boost electrical signal speeds in computers and telecommunications grids by more than 50 per cent.

Electrons usually travel at about two-thirds of light speed in wires, slowed down as they bump into atoms. Hache says it may be possible to send usable electrical signals to near light speed.

© Copyright Reed Business Information Ltd.

[balrog666]

Anybody got a clue here?

And I don't see how the oscilloscope can show squat here. Is this just another phase shift masquerade?

[farmfriend]

ping for science fun.

[Rebelbase]

Zephram Cochran won't be born for another 200 years.

[apochromat]

But if it's exactly 13 minutes past the hour here, then it's exactly 13 minutes past the hour everywhere on Earth.

[js1138]

I'm sure Physist has addressed the known phenomenon. I'm sure he'll say no information is transmitted faster than light. Note the the folks announcing the experiment do not make this claim. Wish I understood it.

[prisoner6]

"In a related announcement, the staff of Middle Tennessee State University have 'solved' the Unified Field Theory utilizing six soda straws, three empty beer cans, a ten-year-old Timex man's watch (leather band), twenty feet of plastic tubing (1/4" diameter), and duct tape."

Johnny-come-latelys! What took 'em so long? Heck my friends and I did that years ago, although admittedly we used a much more expensive, and almost as complex, Timex-Sinclair computer instead of a watch.

prisoner6

[VadeRetro]

It looks like a clash between two wavefronts rippling along the front collision, rather like a thought experiment I've seen before. Imagine two vast sheets of plywood floating in space with the near edges only slightly separated. At one end, the separation is four inches. At the other end, the separation is one inch. This is because one sheet is very slightly out of square, whereas the other is perfect.

Accelerate one sheet so that it passes under the other one. The one-inch gap is closed first. The visible separation between the sheets disappears at a "point" which ripples along the boundary of the upper sheet at speeds not constrained by the speed of light. If you accelerate the sheets together at near light speed, the "point" flies at some amazing hypervelocity. But it's not a real object or even a real signal.

I may be misinterpreting the main article, but that's what I get from the "interference" between two wave fronts.

[Myrddin]

Light doesn't travel the same speed through coax as it does through free space. There is a characteristic called "velocity factor". Light travels at about 2/3 the speed through coax compared to free space in RG8/U coax. I don't think the parties writing the article finished their basic electricity/electronics courses.

[staytrue]

This experiment is not breaking the speed of light. They are using mulitple pulses that travel back and forth on a wave guide that sets up an interference pattern with a pattern where the main bump "moves" faster than light. It actually is not moving at all, it was always there.

[staytrue]

Dang, you beat me by a minute, but I agree with you.

[Sinner6]

Doesn't Einstein's theory imply that if something travels faster than the speed of light, it would travel backward in time?

Einstein’s theory often predate quantum mechanics and thusly quantum mechanics will cause "discrepancies" with standard Einsteinion physics. And thus very small amounts of matter and/or energy may react in very odd ways, see Schrodinger's cat. Also in the most extreme situations of quantum mechanics cause and effect are not clear and it can appear that cause fallows effect.

[woofie]

Heck, I had a professor at Muleshoe Community College who once figured out "what women want" and sustained it for 14 hours 27 minutes and he only used a bottle opener and some WD40.

[apochromat]

Imagine two vast sheets of plywood floating in space

That was the easy part. I think they already tried that at Maimi U.

[You Gotta Be Kidding Me]

When someone builds a spacecraft that goes 100 times the speed of light, the "science" community will still act like spin doctors in their attempts to save face for their pagan god, Einstein. It's pathetic. Science is rooted in the laws (known and unknown) of nature, not in some crotchety dead guy with a white beard.

[sharktrager]

screw the warp drive...i want the holodeck!

[js1138]

This reminds me of a question I have about Star Wars Physics. Has anyone ever calculated the apparent speed of the wave front in the exploding planet? My guess is the debris cloud is traveling considerably faster than the speed of light.

[unixfox]

Just think of all the bounced e-mail !!

[balrog666]

This experiment is not breaking the speed of light. They are using mulitple pulses that travel back and forth on a wave guide that sets up an interference pattern with a pattern where the main bump "moves" faster than light. It actually is not moving at all, it was always there.

Hummm, then why the "news release"? Did they think it was April First?

[XNavyNuc]

Kinda hard to transmit light through RG anything... The whole point of the article is to show that 'something' can be propagated faster than 300 M m/sec. In this case a wavefront might be able to carry 'intelligence'. Think of a tsunami, where the 'wavefront' travels at, say, 600 mph across the ocean... and then it reaches a shorefront where the energy contained in the fast wavefront is converted into simple mechanical energy (height of water and forward speed). Got that? Probably not. Oh, well.

[bcoffey]

While the peak moves faster than light speed, the total energy of the pulse does not.

It must have been a slow news day.

The article is describing the faster-than-light travel of phase velocity, not group velocity. It is the latter that would be useful in transmitting information. The article even states this, though the press seems not to have cared.

A faster-than-light phase velocity has been around for a very long time. A more pedestrian analogy would be ocean waves striking the shore at an angle. If you followed the crest of the wave as it struck the shore, you'd find it was traveling faster than the velocity of the wave itself.