Courtesy of Holger
Müller
The researchers
conducted tests inside a sophisticated vacuum chamber.
An aluminum sphere
(center), helped suppress dark energy fields called “chameleon fields.”
Scientist uses cold atoms to probe dark energy, which is responsible
for the acceleration of the universe
(August 20, 2015) Besides
the atoms that make up our bodies and all of the objects we encounter in
everyday life, the universe also contains mysterious dark matter and dark
energy. The latter, which causes galaxies to accelerate away from one another,
constitutes the majority of the universe’s energy and mass.
Ever since dark energy was discovered in 1998, scientists
have been proposing theories to explain it — one is that dark energy produces a
force that can be measured only where space has a very low density, like the
regions between galaxies.
Enar de Dios
Rodriguez
Paul Hamilton
(foreground), now a UCLA professor,
in the lab with
his UC Berkeley colleagues.
Paul Hamilton, a UCLA assistant professor of physics and
astronomy, reproduced the low-density conditions of space to precisely measure
this force. His findings, which helped to reveal how strongly dark energy
interacts with normal matter, appear today in the online edition of the journal
Science.
Hamilton’s research focuses on the search for specific types
of dark energy fields known as “chameleon fields,” which exhibit a force whose
strength depends on the density of their surrounding environment. This force,
if it were proven to exist, would be an example of a so-called “fifth force”
beyond the four known forces of gravity, electromagnetism, and the strong and
weak forces acting within atoms.
But this fifth force has never been detected in laboratory
experiments, which prompted physicists to propose that when chameleon fields
are in dense regions of space — for example, the Earth’s atmosphere — they
shrink so dramatically that they become immeasurable.