A discarded SpaceX rocket stage, left adrift after completing its mission over a year ago, will collide with the moon Wednesday at 5,400 miles per hour — not by design, but by the quiet, indifferent pull of gravity. Near Einstein Crater, the impact will carve a small but telling scar into the lunar surface, one that scientists intend to read carefully. It is a moment that sits at the intersection of human ambition and human oversight, arriving just as the moon is becoming less a distant symbol and more a contested frontier.