Gravitational waves simulation

Accelerating masses send ripples through spacetime itself. A pair of black holes orbiting each other loses energy to these waves, spirals inward faster and faster, and finally merges. LIGO first detected exactly this in 2015.

Interactive, free and runs in your browser. Part of the General Relativity simulations.

What you will see

Two black holes inspiral, merge and ring down while a two-armed spiral of waves ripples outward across a gridded sheet. Each point shows the wave as it was emitted earlier, because the waves take time to travel. Far out, a ring of free test masses is stretched one way and squeezed the other as the wave passes, and a strain plot shows the rising chirp and the ringdown.

Try this

  1. Watch the strain plot: the wiggles get faster and taller until the merger.
  2. Follow one wave crest outward and watch the test-mass ring respond when it arrives.
  3. Increase the mass and compare the strength and speed of the chirp.

Common misconception

Gravitational waves are not sound or vibrations in a material. They stretch and squeeze space itself, by a strain of around 10⁻²¹ for the strongest events reaching Earth.

Exam-style question

A gravitational wave with strain h = 1.0 × 10⁻²¹ passes a LIGO arm 4.0 km long. Roughly how much does the arm length change?

ΔL ≈ hL = 1.0 × 10⁻²¹ × 4.0 × 10³ m = 4.0 × 10⁻¹⁸ m, hundreds of times smaller than the diameter of a proton.

Key equations

  • h = ΔL / L
  • f_GW = 2 f_orbit

Curriculum

Enrichment beyond A-level, IB Physics A.5.

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