A discarded SpaceX rocket stage, adrift since early 2025, will collide with the moon Wednesday near Einstein Crater at 5,400 miles per hour — an unplanned event that scientists are quietly reframing as a lesson. In the long arc of human ambition toward the stars, this moment sits at the intersection of carelessness and curiosity: a piece of forgotten machinery becoming, in its final seconds, an instrument of knowledge. As nations race to return humans to the lunar surface, the crash asks a question humanity has not yet fully answered — who is responsible for the space we leave behind?