Gravity remains one of the most mysterious and less understood forces in the universe. While Einstein spent a big chunk of his career laying the foundation of how it works in his general theory of relativity, which he published in 1916, the science community hasn't done much to advance the state of the knowledge now almost a century old.
In fact, we still haven't been able to prove in experiments some of the effects that the general theory of relativity predicts, case in point, gravity waves.
Einstein's theory predicts that the gravity of large enough bodies creates ripples in spacetime, distorting the very fabric of the universe.
These ripples would propagate as waves, as any other wave that we know of. While the effects of gravity on the nature of space have been proven, gravitational lensing, time slowing down or speeding up and so on, the waves generated by gravity are so small that it's been impossible to see their effect.
Atomic interferometry could change that. A team of scientists at the NASA Goddard Space Flight Center, Stanford University and AOSence, have gotten funding from NASA's Innovative Advanced Concepts program, to devise equipment and experiments for detecting gravitational waves.
The effect of these waves on something like our Earth for example is so small that the planet only shrinks and then expands by less than the width of an atom.
Obviously, detecting that sort of movement is close to impossible on most places on Earth and in most cases. There are so many external factors, earthquakes or the ocean tides, that are more powerful, that it's very hard to isolate them.
This is where atom interferometry comes in. The technique is similar to optical interferometry in concept. In the latter, two light beams travel along two paths, one unobstructed, one going through the object you want to measure.
The two beams are identical, but one is altered by the objects it encounters in its path. As such, when it arrives at its destination, it arrives altered, merges with the other beam, and creates interference, which is then analyzed to deduce various properties of the object being measured.
Atom interferometry works in the same way but, you guessed it, with atoms. The atoms are cooled to a very low energy state. They are then put in a quantum superposition and sent along different paths. When they arrive at their destination, any differences between the paths they took, which in theory should be equal, will create an interference pattern, due to the atoms' wave nature.
These instruments are capable of detecting even the tiniest changes in distance and should be capable of detecting the effects of gravitational waves. It's certainly not a new idea, the difference is that there is now someone actually working on it.
The first experiments will happen at Stanford University where the team will be testing the laser they built for this type of experiment. The laser is used to cool down the atoms and then manipulate them.
The plan is to eventually build a very sensitive atom interferometer in space, where there would be fewer "noise" sources and where it could be used to study the gravitational effects of various objects, including asteroids, as well as, obviously, look for gravitational waves.