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By tweaking the relationship between phase velocities, it’s possible to adjust the group velocity and create the illusion that parts of the pulse are travelling faster than the speed of light.
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 733 June 15, 2005 by Phillip F. Schewe, Ben Stein
LIGHT MAY ARISE FROM TINY RELATIVITY VIOLATIONS, according to a new
theory. Speaking most recently at last month's American Physical
Society meeting of the Division of Atomic, Molecular, and Optical
Physics in Nebraska, Alan Kostelecky of Indiana University (812
855-1485, KOSTELEC@INDIANA.EDU) described how light might exist as a
result of breaking an assumption of relativity theory known as
Lorentz symmetry. In Lorentz symmetry, the laws of physics stay the
same even when you change the orientation of a physical system (such
as a barbell-shaped molecule) or alter its velocity. According to
special relativity, the speed of light is the same in every
direction, a notion that current experiments verify to a few parts
in 10^16. However, if physicists find variations in the speed of
light with direction, this would provide evidence for broken Lorentz
symmetry, which would radically revise notions of the universe.
Broken Lorentz symmetry would give spacetime a preferred direction.
In its simplest form, broken Lorentz symmetry could be visualized as
a field of vectors (arrows) existing everywhere in the universe. In
such a picture, objects might behave slightly differently depending
upon their orientation with respect to the vectors. In a recent
paper, published in Physical Review D (Bluhm and Kostelecky,
Physical Review D, 71, 065008, published 22 March 2005), the authors
propose that the veryexistence of light is made possible through a
vector field arising
from broken Lorentz symmetry. In this picture, light is a
shimmering of the vector field analogous to a wave blowing through a
field of grain (see animation at
www.physics.indiana.edu...). The researchers
have shown that this picture would hold in empty space as well as in
the presence of gravity (curved spacetime) which is often ignored in
conventional theories of light. This theory is in contrast to the
conventional view of light, which arises in a space without a
preferred direction and as a result of underlying symmetries in
particles and force fields. Kostelecky says that the new theory can
be tested by looking for minute changes in the way light interacts
with matter as the earth rotates (and changes its orientation with
respect to the putative vector field). In addition, Kostelecky says
that neutrino oscillations might arise from interactions between
neutrinos and the background vector field, as opposed to the
conventional explanation, which invokes neutrino mass as the
explanation for the oscillations. Experimentalist Ron Walsworth of
Harvard-Smithsonian comments that the nice thing about Kostelecky's
work is that he proposes detailed experiments to test his theories;
and that the results of such experiments, no matter how they turn
out, promise to deepen our understanding of physics. (For more
information, see article by Kostelecky in the Scientific American,
September 2004; as well as Indiana University Press Release, March
Originally posted by Rren
Visible light of course is only in a narrow frequency range. The existence of light is not in question ... whether we model our world with or without the Lorenz symmetry simplications will not change the way "light" exists, but it will certainly change the equations we use to predict it.
On the other hand, the speed of light constant is in fact not entirely constant. It's constant today and will be tomorrow, and for a long long time, but eventually the expansion of the universe and the cooling associated with it will modify the resistance (permittivity) of free space which will indeed change this constant, but not by a whole lot. This is a revolutionary new concept in cosmology that is only being developed in recent years.
Originally posted by Rren
1) When you say "..it will certainly change the equations we use to predict it.", could you elaborate on that?
2) Are we talking about fundamental changes like the age of the stars/universe?
3) Is this change in constancy of light(?) and Lorenz symmetry already taken into account when 'dating' distant stars and galaxies?
4) It would affect parralax measurements and perceived brightness of cepheid variable stars would it not? Both key in 'dating' distant stars, correct?
I like to read alot about physics and cosmology but am not formally educated in either, so sorry if this was a stupid question.