dreskir
08-15-2001, 09:10 AM
cosmic laws like speed of light might be changing, a study finds
by james glanz and dennis overbye
n 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 particles.
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 cosmos.
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 physics."
dr. webb added, "if it's correct, it's the result of a lifetime."
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 cart."
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
within atoms.
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
clouds.
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 constant.
"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 complicated matter.
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 believe them.
"after much thinking about this issue," dr. bekenstein said, "i think
the quasar observations may have found the real variation."
by james glanz and dennis overbye
n 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 particles.
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 cosmos.
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 physics."
dr. webb added, "if it's correct, it's the result of a lifetime."
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 cart."
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
within atoms.
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
clouds.
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 constant.
"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 complicated matter.
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 believe them.
"after much thinking about this issue," dr. bekenstein said, "i think
the quasar observations may have found the real variation."