Ripples in the fabric of spacetime
Accelerating masses send ripples through spacetime itself. In 2015 LIGO caught one from two black holes merging 1.3 billion light-years away.
Watch two objects spiral in, merge, and ring down while ripples spread across the mesh: blue is compression, amber is stretching. Change the mass ratio and playback speed.
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.
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.
Switch between the plus and cross modes and watch a ring of test particles stretch one way while squeezing the other. Adjust the amplitude and frequency.
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.
Turn the gravitational wave on and watch one arm stretch while the other shrinks, shifting the interference pattern at the detector.
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.
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.
Set the two masses and press Play Chirp to hear the signal sped up to an audible tone. Notice how the masses change how fast the pitch sweeps upward before it cuts off 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.
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.
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