LISA would detect ripples in space-time proposed by Einstein's theory of general relativity. Gravitational waves flow outward from collisions of huge celestial bodies like black holes and binary systems, but there is no way to prove their existence or study them. LISA would have involved three identical spacecraft arrayed in a triangle, spaced 3.1 million miles apart. As gravitational waves reach the observatory, they warp space-time, stretching or compressing the triangle. Measuring the spacecraft's separation would allow physicists to measure the waves. LISA would also have detected binary systems and helped scientists measure black hole collisions.