A few years ago, an early morning fireball lit up the sky over Chelyabinsk, Russia. Shock waves from the impact shattered windows, injuring over a thousand people. Now this wasn’t the first time such a thing had happened. A hundred and nine years ago, something really big blew up in the atmosphere above the Tunguska region in Siberia. Reports from June 30th, 1908 sound a lot like the Chelyabinsk event. A brilliant blue light, like a second sun, flashed across the early morning sky. This was followed by a sonic shock wave that broke windows, killed wildlife, knocked people to the ground, and shook the earth. The Chelyabinsk impactor was a rock over fifty feet across. It came in at about 40,000 miles an hour – slow for a meteor – and it broke apart about ten to 15 miles above the surface. The total energy of the blast was roughly equal to a dozen or more atomic bombs. The Tunguska blast was at least five hundred times more powerful.