Astronomers Gain Clues About Fundamental Physics (Forwarded)

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December 19, 2005

Astronomers Gain Clues About Fundamental Physics

An international team of astronomers has looked at something very big --
a distant galaxy -- to study the behavior of things very small -- atoms
and molecules -- to gain vital clues about the fundamental nature of our
entire Universe. The team used the National Science Foundation's Robert
C. Byrd Green Bank Telescope (GBT) to test whether the laws of nature
have changed over vast spans of cosmic time.

"The fundamental constants of physics are expected to remain fixed
across space and time; that's why they're called constants! Now,
however, new theoretical models for the basic structure of matter
indicate that they may change. We're testing these predictions." said
Nissim Kanekar, an astronomer at the National Radio Astronomy
Observatory (NRAO), in Socorro, New Mexico.

So far, the scientists' measurements show no change in the constants.
"We've put the most stringent limits yet on some changes in these
constants, but that's not the end of the story," said Christopher
Carilli, another NRAO astronomer.

"This is the exciting frontier where astronomy meets particle physics,"
Carilli explained. The research can help answer fundamental questions
about whether the basic components of matter are tiny particles or tiny
vibrating strings, how many dimensions the Universe has, and the nature
of "dark energy."

The astronomers were looking for changes in two quantities: the ratio of
the masses of the electron and the proton, and a number physicists call
the fine structure constant, a combination of the electron charge, the
speed of light and the Planck constant.

These values, considered fundamental physical constants, once were
"taken as time independent, with values given once and forever" said
German particle physicist Christof Wetterich. However, Wetterich
explained, "the viewpoint of modern particle theory has changed in
recent years," with ideas such as superstring theory and extra
dimensions in spacetime calling for the "constants" to change over time,
he said.

The astronomers used the GBT to detect and study radio emissions at four
specific frequencies between 1612 MHz and 1720 MHz coming from hydroxyl
(OH) molecules in a galaxy more than 6 billion light-years from Earth,
seen as it was at roughly half the Universe's current age. Each of the
four frequencies represents a specific change in the energy level of the
molecule.

The exact frequency emitted or absorbed when the molecule undergoes a
transition from one energy level to another depends on the values of the
fundamental physical constants. However, each of the four frequencies
studied in the OH molecule will react differently to a change in the
constants. That difference is what the astronomers sought to detect
using the GBT, which, Kanekar explained, is the ideal telescope for this
work because of its technical capabilities and its location in the
National Radio Quiet Zone, where radio interference is at a minimum.

"We can place very tight limits on changes in the physical constants by
studying the behavior of these OH molecules at a time when the Universe
was only about half its current age, and comparing this result to how
the molecules behave today in the laboratory," said Karl Menten of the
Max-Planck Institute for Radioastronomy in Germany.

Wetterich, a theorist, welcomes the new capability, saying the
observational method "seems very promising to obtain perhaps the most
accurate values for such possible time changes of the constants." He
pointed out that, while some theoretical models call for the constants
to change only in the early moments after the Big Bang, models of the
recently-discovered, mysterious "dark energy" that seems to be
accelerating the Universe's expansion call for changes "even in the last
couple of billion years."

"Only observations can tell," he said.

This research ties together the theoretical and observational work of
Wetterich and Carilli, this year's winners of the prestigious Max Planck
Research Award of the Alexander von Humboldt Foundation and the Max
Planck Society in Germany. Menten and Carilli have collaborated on
research in this area for years, and Kanekar has pioneered the OH
molecular technique.

Kanekar, Carilli and Menten worked with Glen Langston of NRAO, Graca
Rocha of the Cavendish Laboratory in the UK, Francoise Combes of the
Paris Observatory, Ravi Subrahmanyan of the Australia Telescope National
Facility (ATNF), John Stocke of the University of Colorado, Frank Briggs
of the ATNF and the Australian National University, and Tommy Wiklind of
the Space Telescope Science Institute in Sweden. The scientists reported
their findings in the December 31 edition of the scientific journal
Physical Review Letters.

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