Roughly 50 kilometers east of Baton Rouge, La., lasers ricochet off mirrors that dangle at the ends of a 4-kilometer-long, L-shaped vacuum tube. A nearly identical facility sits almost 3,000 kilometers away in Washington state. The research stations — part of the Laser Interferometer Gravitational-Wave Observatory, or LIGO — are designed to sense gravitational waves, minuscule ripples in the fabric of space. Unlike the recently detected waves from the Big Bang (SN: 4/5/14, p. 6), the waves LIGO picks up will most likely come from black hole or neutron star collisions.