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arXiv · 0806.4938

Observation of negative impulse velocity in free space

Neil V. Budko
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Abstract

Since the 1983 definition of the speed of light in vacuum as a fundamental constant with the exact value of 299792458 m/s the question remains as to what apart from the wavefront travels at that speed. It is commonly assumed that the entire wave-packet or an impulse of the electromagnetic radiation in free space does. Here it is shown, both theoretically and experimentally, that there exists a region close to the source, where, while the wave-front travels at the speed of light, the individual impulses comprising the body of the wave-packet appear to slow down and even go backwards in time. This three-dimensional near-field late-time effect may also explain some of the free-space superluminal measurements.

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Neil V. Budko. 2008-07-01. Observation of negative impulse velocity in free space. https://doi.org/10.1103/physrevlett.102.020401

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