Path of Totality: Umbra Footprint & Ground-Track Speed

Every total solar eclipse traces a track across Earth's surface, and that track's width and speed are not constant — they depend on exactly where and when the Moon's umbra cone meets the curved ground. This simulator renders the umbra as a real converging shadow beam striking a true-to-scale Earth, computing the across-track footprint width from the umbra's actual length and the Moon's current orbital distance, then stretching it into an ellipse and accelerating its ground track using the same foreshortening geometry that makes a sunset shadow race across the ground. A crossing-latitude control folds in Earth's own rotation, and live readouts show the resulting footprint dimensions, ground-track speed, and — from simply dividing one by the other — the duration of totality at that point on the track.