SYDNEY (Reuters) - A team
of Australian scientists has proposed that the speed of light may not be
a constant, a revolutionary idea that could unseat one of the most cherished
laws of modern physics -- Einstein's theory of relativity.
The team, led by theoretical physicist Paul Davies of Sydney's Macquarie
University, say it is possible that the speed of light has slowed over
billions of years.
If so, physicists will have to rethink many of their basic ideas about
the laws of the universe.
"That means giving up the theory of relativity and E=mc squared and
all that sort of stuff," Davies told Reuters.
"But of course it doesn't mean we just throw the books in the bin,
because it's in the nature of scientific revolution that the old theories
become incorporated in the new ones."
Davies, and astrophysicists Tamara Davis and Charles Lineweaver from the
University of New South Wales published the proposal in the August 8 edition
of scientific journal Nature.
The suggestion that the speed of light can change is based on data collected
by UNSW astronomer John Webb, who posed a conundrum when he found that
light from a distant quasar, a star-like object, had absorbed the wrong
type of photons from interstellar clouds on its 12 billion year journey
Davies said fundamentally Webb's observations meant that the structure
of atoms emitting quasar light was slightly but ever so significantly different
to the structure of atoms in humans.
The discrepancy could only be explained if either the electron charge,
or the speed of light, had changed.
IN TROUBLE EITHER WAY
"But two of the cherished laws of the universe are the law that electron
charge shall not change and that the speed of light shall not change, so
whichever way you look at it we're in trouble," Davies said.
To establish which of the two constants might not be that constant after
all, Davies' team resorted to the study of black holes, mysterious astronomical
bodies that suck in stars and other galactic features.
They also applied another dogma of physics, the second law of thermodynamics,
which Davies summarizes as "you can't get something for nothing."
After considering that a change in the electron charge over time would
violate the sacrosanct second law of thermodynamics, they concluded that
the only option was to challenge the constancy of the speed of light.
More study of quasar light is needed in order to validate Webb's observations,
and to back up the proposal that light speed may vary, a theory Davies
stresses represents only the first chink in the armor of the theory of
In the meantime, the implications are as unclear as the unexplored depths
of the universe themselves.
"When one of the cornerstones of physics collapses, it's not obvious
what you hang onto and what you discard," Davies said.
"If what we're seeing is the beginnings of a paradigm shift in physics
like what happened 100 years ago with the theory of relativity and quantum
theory, it is very hard to know what sort of reasoning to bring to bear."
It could be that the possible change in light speed will only matter in
the study of the large scale structure of the universe, its origins and
For example, varying light speed could explain why two distant and causally
unconnected parts of the universe can be so similar even if, according
to conventional thought, there has not been enough time for light or other
forces to pass between them.
It may only matter when scientists are studying effects over billions of
years or billions of light years.
Or there may be startling implications that could change not only the way
cosmologists view the universe but also its potential for human exploitation.
"For example there's a cherished law that says nothing can go faster
than light and that follows from the theory of relativity," Davies
said. The accepted speed of light is 300,000 km (186,300 miles) per second.
"Maybe it's possible to get around that restriction, in which case
it would enthrall Star Trek fans because at the moment even at the speed
of light it would take 100,000 years to cross the galaxy. It's a bit of
a bore really and if the speed of light limit could go, then who knows?
All bets are off," Davies said.
Copyright 2002 Reuters News Service. All rights reserved.
This material may not be published, broadcast, rewritten, or redistributed.
From John Albrecht
Of course the speed of light isn't constant. It never
It can change depending on the density of the
medium it is traveling in as well as gravimetric flux.
In other words, external factors can affect the observed
speed of light.
Considering that the age of the photons they measured
was 12 BILLION years, a lot could have happened to those photons in that
period of time.
Consider also that the density of the universe isn't constant,
that the density hasn't been constant as it expands, and that the gravimetric
flux changes not only as one travels through it, but because the universe
itself is expanding (see note). Perhaps the photons passed through a gravimetric
lens of which we aren't yet aware or some other phenomenon.
Perhaps some phenomenon we haven't seen before drifted in
and then out of the path of the photons on their way to Earth. Perhaps
there is an interaction with "dark matter" which is a newly developing
field of theoretical study.
(Note: an expanding universe poses an interesting observation.
One might assume that as the universe expands, the density decreases because
it is occupying an increasing volume, and hence, the speed of light "should"
increase over time as the density decreases. However, one might also observe
that in some areas the density might actually increase as atoms of
matter tend to distribute more homogeneously throughout the volume
of space, and thereby actually result in an increased apparent density
thereby resulting in an apparent reduction in the speed of light over time,
as Davies et al has said.)