What mysterious explosion flattened 80 million trees in Siberia in 1908?

At 07:17 a.m. on 30 June 1908, a blinding fireball streaked over the Stony Tunguska River. Seconds later, a mid-air explosion—now estimated at up to 50 megatons, 1 000× Hiroshima—flattened 80 million trees in a radial pattern visible from space. Shockwaves rattled windows in Moscow and registered on barographs worldwide.

No crater appeared, fuelling a century of speculation: comet fragment? Alien craft? Nikola Tesla’s death-ray test? Only in the 1990s did computer models confirm that a 50-metre stony asteroid had vaporised 5–10 km up, sparing Earth a catastrophic impact but giving us the loudest cosmic wake-up call on record.

Tunguska remains a planetary-defence poster child: if an asteroid that small could fell a forest the size of Luxembourg, humanity’s sky-watching budget suddenly looks like petty cash.