The new precision tool with a variety of applications will serve to test Einstein's Theory of Relativity, and it's called atom interferometry.

Interferometry is the science and technique of superposing (interfering) two or more waves, which creates an output wave different from the input waves, which in turn can be used to explore the differences between the input waves. Because interference is a very general phenomenon with waves, interferometry can be applied to a wide variety of fields, including astronomy, fiber optics, optical metrology, oceanography and various studies of quantum mechanics applications. Interferometry can be applied to both one-dimensional waves such as time varying signals, or to multi-dimensional waves such as coherent images produced by laser illumination.

Savas Dimopoulos, a physics professor at Stanford University 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: "Atom interferometry is an exciting field which has been awarded three Nobel prizes in the last decade. 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," he said.

Current general relativity tests are performed 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."

Trying to speed up the analysis, they are 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."

Scientific theories are always evolving, the way general relativity modified Newton's ideas of gravity, so finding something that modifies general relativity would be the next huge step in science.