The faster than light beam

Discussion in 'Physics & Math' started by atomka, Oct 28, 2001.

  1. atomka Registered Member

    have we all read/heard about the men who accelerated a beam of light past the speed of light? Unfortunately people have speculated that this could be the first step to time travel. But, what people don't realize that have just read the aricle, or have not followed up on it, is that we cannot accelerate matter to that speed. Any thoughts or comments?
  2. Google AdSense Guest Advertisement

    to hide all adverts.
  3. John Devers (AVATAR) Registered Senior Member

    Yep, that's right, it's just the propagation wave that of the light beam that travels faster than light.

    This exerpt from an article by the experimenters may interest you.

    A light pulse is made of many wave components of different wavelength (frequency). First in air, all three waves are in phase in region-1 where the waves add to produce a pulse. Slightly further in space along its propagation direction, the waves become "out of phase" and the waves cancel each other.

    In an anomalous dispersion region (Region-2 inside the Cesium atomic cell), a wave which has shorter wavelength in vacuum (wave-1) now has a longer wavelength. Conversely, a longer wavelength wave (wave-3) becomes a shorter wavelength wave. Hence the waves’ phase are accordingly modified.

    When the three waves emerge again from the Cesium cell’s exit surface, they restore their wavelengths. Due to the unusual phase modulation of the anomalous dispersion material, the three waves are in phase again in a third region (Region-3 in air). In this region, the three waves again add to produce the exact form of the incoming pulse.

    Ordinarily in air and as a matter of fact in all normal dispersion materials, a light pulse cannot re-phase to appear at a distant place along its propagation direction.

    Normally, the light pulse will appear at such a distant place along its propagation at a later time. However, owing to the extraordinary properties of an anomalous dispersion material, a light pulse can rephase to appear at such a distant place along its propagation direction.

    Thus the light pulse behaves as if it takes a negative time to traverse the distance in between.
  4. Google AdSense Guest Advertisement

    to hide all adverts.

Share This Page