A gravitational wave can't be aimed at — it arrives from a direction you don't know, sweeping across every detector a few milliseconds apart. You recover where it came from by timing: the tiny delays between stations pin the sky direction, and the longer the baseline between them, the sharper the pin. Earth's detectors sit a few thousand km apart. Put one on the Moon and the baseline jumps 128×. Drag the source and watch the localization tighten.