Cosmic Laws Like Speed of Light Might
Be Changing, a Study Finds
The New York Times
James Glanz and Dennis Overbye
Copyright The New York Times
August 15, 2001
An international team of astrophysicists has discovered that the basic laws
of nature as understood today may be changing slightly as the universe ages, a
surprising finding that could rewrite physics textbooks and challenge fundamental
assumptions about the workings of the cosmos.
The researchers used the world's largest single
telescope to study the behavior of metallic atoms in gas
clouds as far away from Earth as 12 billion light years.
The observations revealed patterns of light absorption
that the team could not explain without assuming a
change in a basic constant of nature involving the
strength of the attraction between electrically charged
If confirmed, the finding could mean that other
constants regarded as immutable, like the speed of light,
might also have changed over the history of the
The work was conducted by scientists in the United
States, Australia and Britain and was led by Dr. John K.
Webb of the University of New South Wales in Sydney,
Australia. It is to be published on Aug. 27 in the field's
most prestigious journal, Physical Review Letters.
Scientists who have examined the paper have not been
able to find any obvious flaws. But because the
consequences for science would be so far-reaching
and because the differences from the expected
measurements are so subtle, many scientists are
expressing skepticism that the discovery will stand the
test of time, and say they will wait for independent
evidence before deciding whether the finding is true.
On the other hand, the finding would fit with some
theorists' new views of the universe, particularly the
prediction that previously unknown dimensions might
exist in the fabric of space.
Even scientists on the project have been deliberately
cautious in presenting their result. Describing the
implications of what his team observed, Dr. Webb said,
"It's possible that there is a time evolution of the laws of
Dr. Webb added, "If it's correct, it's the result of a
Dr. Rocky Kolb, an astrophysicist at the Fermi National
Accelerator Laboratory who was not involved in the
work, said the finding could not only force revisions in
cosmology, the science of how the universe began and
later evolved, but also add credence to an unproven
theory of physics called string theory, which predicts
that extra dimensions exist.
"The implication, if it is true, would just be so enormous
that it's something people should look at and take
seriously," Dr. Kolb said. "This would upset the apple
The magnitude of the change apparently observed by
the group is minute, amounting to just 1 part in 100,000
in a number called the fine structure constant over 12
billion years. That constant, also referred to as alpha, is
defined in terms of more familiar quantities like the
speed of light and the strength of electronic attractions
But even that small change would rock physics and
cosmology, said Dr. Sheldon Glashow of Boston
University, who received a Nobel Prize in physics in
1979. The importance of such a discovery, Dr. Glashow
said, would rank "10 on a scale of 1 to 10."
Considering the unexpected nature of the finding, both
Dr. Glashow and Dr. Kolb said the chances were high
that some more mundane explanation for the results
would turn up.
Dr. John Bahcall, an astrophysicist at the Institute for
Advanced Study in Princeton, N.J., said the
complicated analysis that was required to infer the tiny
changes from the observations could - in principle, at
least - be obscuring possible errors.
"The effect does not scream out at you from the data,"
Dr. Bahcall said. "You have to get down on all fours and
claw through the details to see such a small effect."
But others said that the team had been very careful and
that any unknown source of error would have to be
extremely subtle to be missed.
"If they were claiming anything less dramatic, probably
most people would find their work very careful and
believable," said Dr. Massimo Stiavelli, an astrophysicist
at the Space Telescope Science Institute in Baltimore.
"Exceptional results deserve extraordinary proof," Dr.
Stiavelli said, adding that he was reserving judgment
until further evidence became available.
The work relied on observations of light from distant
beacons called quasars, which shine with a brightness
equivalent to billions of suns. The light is probably
emitted by matter torn from young galaxies by the
powerful gravity of a black hole.
Besides Dr. Webb, the team included three other
scientists at the University of New South Wales, Michael
T. Murphy, Dr. Victor V. Flambaum, and Dr. Vladimir A.
Dzuba; and one physicist at Cambridge University in
Britain, Dr. John D. Barrow. Three American
astronomers who are experts on quasars were also
members of the team: Dr. Christopher W. Churchill of
Pennsylvania State University; Dr. Jason X. Prochaska
of the Carnegie Observatories; and Dr. Arthur M. Wolfe
of the University of California at San Diego.
The observations, made by the 30- foot-wide Keck
Telescope on Mauna Kea, in Hawaii, looked in detail at
the absorption of quasar light by gas clouds in deep
space between Earth and the quasars. Metal atoms like
zinc and aluminum are often present in trace amounts in
The absorption of light by such atoms creates dark
spikes at various wavelengths in the quasar's spectrum,
with a pattern so well defined that it is often likened to a
fingerprint. The value of those wavelengths is directly
related to the value of the fine structure constant.
But the fingerprint seemed to change in time, Mr.
Murphy said, indicating that the constant grows larger
as one goes nearer to the present and was not really
"What we have found is that, statistically, there is a
difference between the fine structure constant a long
time ago and here on earth," he said.
Far from being of interest only in understanding atomic
behavior, said Dr. Barrow of Cambridge University, the
effect would be important "because it gives you such a
feedback into fundamental physics."
String theory, for example, could accommodate
changes in quantities that accepted physics theory
considers immutable. String theorists postulate that
space contains tiny, unseen dimensions. Any change in
the size of those dimensions - much like the expansion
of the universe in the space we are familiar with - could
change quantities like the fine structure constant, said
Dr. Paul Steinhardt, a physicist at Princeton University.
Dr. Steinhardt said most theorists would have expected
those changes to have occurred in the first seconds of
the universe's life and be virtually unobservable by
astronomers today. Still, he pointed out that several
years ago, other astronomers unexpectedly found that
the present universe is apparently filled with a
mysterious kind of energy that counteracts gravity on
large scales. Perhaps the two effects are somehow
related, Dr. Steinhardt said.
Other scientists pointed out that geologic processes,
like naturally occurring nuclear fission, have been used
to determine that the fine structure constant has
probably changed little over the past two billion years
on Earth. But researchers on the new paper point out
that their results reach back much farther in time, and
that interpreting the geological results is also a
But a few physicists, like Dr. Jacob D. Bekenstein of
Hebrew University in Israel, noted that some theories
have long been predicting a change in some of nature's
apparent constants. Dr. Bekenstein called the findings
"potentially revolutionary" and said he was inclined to
"After much thinking about this issue," Dr. Bekenstein
said, "I think the quasar observations may have found
the real variation."
Professor Arthur Wolfe (858) 534-7435