Gravitational Wave Calculator

LIGO detects a gravitational wave by watching two 4-kilometer laser arms stretch and squeeze by about one part in 10²¹ — a distortion roughly a thousand times smaller than the width of a proton. That signal only becomes trustworthy because the same waveform has to show up in detectors thousands of kilometers apart, letting a real chirp be told apart from local noise like passing trucks or distant earthquakes. The frequency doesn't stay put either: as the two objects spiral inward, orbital energy bleeds away as gravitational radiation, so the wave sweeps upward in frequency right up to merger — the 'chirp' this tool's curve is named for.

When two compact objects spiral together they don't broadcast their two masses separately. The waveform is set almost entirely by one combination, the chirp mass M_c = (m₁m₂)^3/5/(m₁+m₂)^1/5. That single number controls how fast the frequency sweeps upward, so measuring the rate of the chirp hands you the chirp mass directly — which is why this tool puts it front and centre.

The amplitude of a gravitational wave depends on the source's true luminosity distance in a way physicists can compute from first principles — no calibration against Cepheids or supernovae required. That makes each merger a standard siren: read the chirp for the masses, read the amplitude for the distance. Pair that with a redshift and you get an independent measurement of the Hubble constant — exactly how the 2017 neutron-star merger GW170817 weighed in on how fast the universe expands.