|Speed of Light Broken with Basic Lab Kit|
by Charles Choi
10:03 16 September 02
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 meters 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 meters, 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 tunneling through the cable at more than four billion kilometers 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 © 2010