Gravitational Waves Gain Overtones
A guitar string after being plucked produces not only the fundamental note, but also quiet overtones. A similar phenomenon appeared in the gravitational waves from the merger of two black holes (event GW250114).
A Gravitational Call a Minute Before the Merger
A huge pond, with ripples spreading from two heavy stones circling each other. The stones draw closer, the ripples become more frequent and stronger, and soon the stones will collide. Gravitational waves are like those ripples, but not on water — in the very fabric of spacetime.