Faster than light, light

jason rice red666er at hotmail.com
Sat Jul 22 13:23:16 PDT 2000


The Realaudio version is availible on the "All Things Considered" site under archives. The date was Wed. 07/19/00. jason rice


>From: "jason rice" <red666er at hotmail.com>
>Reply-To: lbo-talk at lists.panix.com
>To: lbo-talk at lists.panix.com
>Subject: Re: Faster than light, light
>Date: Sat, 22 Jul 2000 19:58:03 GMT
>
>I heard about the experiment on NPR, they had another physicist come on
>after Wang and say that the experiment did not really exhibit the phenomena
>that the NEC team claimed. According to this gentleman, a tracer of light
>precedes and follows the pulse, and the cesium vapor alters this tracer and
>makes it appear as if the pulse itself is exiting before it has entered the
>chamber. This guy was pretty dismissive of the whole project and noted
>that
>this tracer phenomena had been documented by other researchers in the past.
>Jason Rice
>
>
>>From: Chuck Grimes <cgrimes at tsoft.com>
>>Reply-To: lbo-talk at lists.panix.com
>>To: lbo-talk at lists.panix.com
>>Subject: Faster than light, light
>>Date: Thu, 20 Jul 2000 22:51:26 -0700 (PDT)
>>
>>
>>
>>Gain-assisted superluminal light propagation
>>
>>L. J. WANG, A. KUZMICH & A. DOGARIU
>>
>>NEC Research Institute, 4 Independence Way, Princeton, New Jersey
>>08540, USA
>>
>>Correspondence and requests for materials should be addressed to
>>L.J.W. (e-mail: Lwan at research.nj.nec.com).
>>
>>
>>Einstein's theory of special relativity and the principle of
>>causality(1-4) imply that the speed of any moving object cannot exceed
>>that of light in a vacuum (c). Nevertheless, there exist various
>>proposals(5-18) for observing faster-than- c propagation of light
>>pulses, using anomalous dispersion near an absorption line(4),(6-8),
>>nonlinear(9) and linear gain lines(10-18), or tunnelling
>>barriers(19). However, in all previous experimental demonstrations,
>>the light pulses experienced either very large absorption(7) or severe
>>reshaping(9, 19), resulting in controversies over the
>>interpretation. Here we use gain-assisted linear anomalous dispersion
>>to demonstrate superluminal light propagation in atomic caesium
>>gas. The group velocity of a laser pulse in this region exceeds c and
>>can even become negative(16, 17), while the shape of the pulse is
>>preserved. We measure a group-velocity index of ng = -310(+-5); in
>>practice, this means that a light pulse propagating through the atomic
>>vapour cell appears at the exit side so much earlier than if it had
>>propagated the same distance in a vacuum that the peak of the pulse
>>appears to leave the cell before entering it. The observed
>>superluminal light pulse propagation is not at odds with causality,
>>being a direct consequence of classical interference between its
>>different frequency components in an anomalous dispersion region.
>>
>>see:
>>
>>http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/
>>v406/n6793/full/406277a0_fs.html
>>
>>-------------------
>>
>>Comments?
>>
>>Chuck Grimes
>
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