A binary black hole inspiral radiates gravitational waves with increasing frequency — the characteristic "chirp." Energy loss via GW emission causes the orbit to shrink, which raises the orbital frequency (Kepler's third law), which increases GW frequency, which causes faster energy loss — a runaway cascade ending in merger. The GW frequency is twice the orbital frequency. The chirp mass M_c = (m₁m₂)^(3/5)/(m₁+m₂)^(1/5) uniquely determines the chirp evolution: f(t) ∝ (t_c − t)^(−3/8). GW150914, the first LIGO detection (2015), had chirp mass ~28.3 M☉ and merged at ~150 Hz.