MOSCOW — Gym class came to a halt inside the Chelyabinsk Railway Institute, and students gathered around the window, gazing at the fat white contrail that arced its way across the morning sky. A missile? A comet? A few quiet moments passed. And then, with incredible force, the windows blew in.

The scenes from Chelyabinsk, rocked by an intense shock wave when a meteor hit the Earth’s atmosphere Friday morning, offer a glimpse of an apocalyptic scenario that many have walked through mentally, and Hollywood has popularized, but scientists say has never before injured so many.