Space-based clouds of atoms: Future gravitational wave detector

A horribly inaccurate artist representation of lasers in space. Still, lasers, in space!

Aurich Lawson / Thinkstock

I've always had a fascination with gravitational wave detection. Gravitational waves are the stretches and contractions in space-time that result from the motion of massive objects. The waves change the apparent distance between two objects as they pass through. But they are tiny—really tiny. To cope with the challenge of detecting something so tiny, gravitational wave observatories have become multi-decade projects that are worked on by large multinational teams. Each generation of sensor is more sensitive than the last, but nothing has been found yet.

In principle, if the first detectors could have seen something, it would have taken a fairly catastrophic event in our local neighborhood. So it's only now that we are starting to reach sensitivities that might reasonably be expected to detect gravitational waves. The big problem is noise. Consider that the typical shift in length caused by a gravity wave is smaller than a hydrogen atom over a few kilometers, and you can see how simple mirror movements and noise in laser systems—lasers are key to making the measurement—could easily swamp the signal.

Indeed, laser noise is a key problem that people have been going to desperate lengths to get around. A new type of interferometer/clock may go a long way to avoiding laser noise.