Article: A new way to test general relativity

A new way to test general relativity

"Atom interferometry is an exciting field which has been awarded three Nobel
prizes in the last decade," Savas Dimopoulos tells PhysOrg.com. "It is a new
precision tool with a variety of applications." Dimopoulos, a physics
professor at Stanford University, wants to use atom interferometry to test
general relativity.

"The unprecedented precision offered allows us to detect the small
deviations that we were previously unable to detect on earth. We will be
able to test Einstein's theory in the lab."

Dimopoulos and his coauthors, Peter Graham, Jason Hogan and Mark Kasevich,
all of Stanford, explore atom interferometry's use in testing the small
effects of general relativity in a Letter titled "Testing General Relativity
with Atom Interferometry," published last month in Physical Review Letters.

Right now, scientists test general relativity by studying astronomical
objects over long periods of time. The theory isn't tested to high levels of
precision and accuracy on earth. "We can't control all the variables with
astronomical tests," explains Dimopoulos. "We cannot shoot Mercury with
different velocities and measure its precession at different rates. In
contrast laboratory experiments have several control parameters, such as the
speed of the atoms and the color of the laser, which allow us to isolate
specific physical effects."

Dimopoulos points out that scientific theories are always evolving. "General
relativity modifies Newton's ideas of gravity, and we may find something
that modifies general relativity." He continues: "If general relativity is
valid when measured at these levels of precision, that would be great. But
sometimes theories breakdown at higher levels of precision. A deviation from
general relativity may suggest new particles whose exchange mediates
corrections to the theory of Einstein. That would be exciting."

Coauthor Kasevich's group is already building an atom interferometry
experiment to test the equivalence principle at 300 times the current limit.
"We're looking at a timeframe of within a year for this first experiment,
which will test whether two objects fall the same way independent of their
mass or constitution," Dimopoulos says. But he and his colleagues won't stop
there. "More detailed experiments will take longer to develop, but they will
come."

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http://www.physorg.com/news95947733.html

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