On the morning of June 30, 1908, an object enters Earth's atmosphere and explodes over a forest in remote Russia.
The force of the blast flattens 80 million trees over an area of 830 square miles. Scientists later estimate the explosion to be 1000 times greater than the atomic bomb dropped over Hiroshima. For weeks, night skies around the world are bright enough to read by, due to dust thrown skyward by the blast.
The origin of the object has been debated ever since, with most scientists concluding this was a comet or asteroid. Differing minority opinions, however, run the gamut from a microscopic black hole to a chunk of antimatter to an alien spacecraft attempting an emergency landing.
This incident is known as the Tunguska Event.