Ripples in the fabric of spacetime
Einstein predicted in 1916 that accelerating masses create ripples in the fabric of spacetime — gravitational waves. These waves travel at the speed of light, stretching and squeezing space as they pass. In 2015, LIGO made the first direct detection: the merger of two black holes 1.3 billion light-years away, opening an entirely new window on the universe.
Two compact objects — neutron stars or black holes — spiral toward each other, radiating energy as gravitational waves. As they lose energy, the orbit tightens: the frequency and amplitude increase in a distinctive chirp. The spiral accelerates until the objects merge in a cataclysmic event, followed by a ringdown as the merged remnant settles.
Drag to orbit the camera, scroll to zoom. Two compact objects spiral inward, emitting gravitational waves that deform the spacetime mesh. Amber regions show positive strain (stretching), blue shows negative strain (compression). After merger, the remnant rings down with decaying oscillations.
Try it: Watch two objects spiral inward while ripples propagate through the spacetime mesh. The color encodes strain — blue for compression, amber for stretching. Adjust the mass ratio and playback speed to explore different scenarios.
Gravitational waves have two polarization modes. The plus mode (h+) stretches space along one axis while compressing the other. The cross mode (h×) does the same but rotated 45°. Together, they describe any gravitational wave.
LIGO uses laser interferometry to detect length changes of 10⁻¹⁸ meters — one-thousandth the diameter of a proton. Two 4 km arms form an L shape. A gravitational wave stretches one arm while compressing the other, creating an interference pattern in the laser light.
LIGO uses laser interferometry to detect gravitational waves. A laser beam is split and sent down two 4-km perpendicular arms. When a gravitational wave passes, it stretches one arm and compresses the other, changing the interference pattern at the detector. The GW150914 signal shown is the first-ever direct detection of gravitational waves from a binary black hole merger.
The gravitational waveform from a binary inspiral encodes the masses and distance of the system. The chirp mass determines how the frequency sweeps upward. Listen to the chirp — when sped up to audible frequencies, it sounds like a rising tone that ends abruptly at merger.
The gravitational wave "chirp" signal from a compact binary inspiral. As the two objects spiral closer, the orbital frequency and wave amplitude increase until coalescence. Click "Play Chirp" to hear a sonified version mapped to audible frequencies. The chirp mass Mc = (m1m2)3/5 / (m1+m2)1/5 determines the evolution.