Prototype beam splitter for the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO)

This is a prototype part for Advanced LIGO, one of the most sensitive experiments ever designed. It will split a laser beam down two paths, several kilometres long. Scientists will look for changes in the path lengths that might be caused by a passing gravitational wave.

Gravitational waves are tiny, fleeting warps in the fabric of space-time, predicted by Einstein’s general theory of relativity. They are caused by moving bodies such as colliding stars.