Listening to the universe
Most of what we know about the universe is carried to us on light waves. But many things are happening that don’t leave clues on the electromagnetic spectrum. That’s where LIGO or the the Laser Interferometer Gravitational-Wave Observatory comes in. Nergis Mavalvala has been working for decades to improve and refine the giant Earth-based observatory in the hopes of catching a gravitational wave and turning on a new sense with which to observe the universe.
Making gravitational waves
Gravitational waves are ripples in spacetime caused by the acceleration and deceleration of enormous masses. Predicted in Einstein's theory of general relativity, gravitational waves have been only observed indirectly. A signal captured by LIGO or other detector would be the first direct contact with a gravitational wave and open up a whole new way of learning about the universe.
Why not use a space-based detector?
It is likely that Earth-based detectors like LIGO can detect gravitational waves from massive sources that are moving very quickly, like black holes and spinning neutron stars. But other sources like the supermassive black holes at the center of galaxies would be better detected from space, because the gravitational waves they emit are at lower frequencies. Earth is just much too noisy for detecting such a small signal. Though several such observatories have been planned, none are currently in operation.