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Hvem tester om dette er rigtigt? - noget pvc-rør og lidt andre "småting"
anvendes i eksperimentet:

"Sound beyond the speed of light: Measurement of negative group velocity
in an acoustic loop filter".
W. M. Robertson,J. Pappafotis, and P. Flannigan
Department of Physics and Astronomy, Middle Tennessee State University,
Murfreesboro, Tennessee 37132
J. Cathey and B. Cathey
Siegel High School, Murfreesboro, Tennessee 37129
C. Klaus
Blackman High School, Murfreesboro, Tennessee 37128
© 2007 American Institute of Physic.
http://www.mtsu.edu/%7Ewroberts/Sound%20beyond%20the%20speed%20of%20light%20Measurement%20of%20negative%20group%20velocity.pdf
Citat: "...
If anomalous dispersion is sufficiently strong the
group velocity can exceed the speed of light. If the transit
time is zero, the peak of the transmitted pulse exits at the
same time as the peak of the incident pulse reaches the input,
and the group velocity is infinite. Finally, in the case of very
strong dispersion, the peak of the transmitted pulse exits be-
fore the peak of the incident pulse reaches the input, and the
group velocity is negative.

It is now generally agreed that all
of these superluminal phenomena do not violate special rela-
tivity or causality and, in particular, it has been shown that
the speed of information transmission is subluminal
[I denne artikel: Under lydhastighed?]
...."

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Sound beyond the speed of light: Measurement of negative group velocity
in an acoustic loop filter
W. M. Robertson, J. Pappafotis, P. Flannigan, J. Cathey, B. Cathey, and
C. Klaus
Appl. Phys. Lett. 90, 014102 (2007) (3 pages)
http://scitation.aip.org/dbt/dbt.jsp?KEY=APPLAB&Volume=90&Issue=1

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http://en.wikipedia.org/wiki/American_Institute_of_Physics

hilsen

Glenn