If the data is correct, we got very, very close (between 600 and 8000km) to a mass extinction event just over a hundred years ago.

On 12th and 13th August 1883, an astronomer at a small observatory in Zacatecas in Mexico made an extraordinary observation. José Bonilla counted some 450 objects, each surrounded by a kind of mist, passing across the face of the Sun.

…

Each fragment was at least as big as the one thought to have hit Tunguska. Manterola and co end with this: “So if they had collided with Earth we would have had 3275 Tunguska events in two days, probably an extinction event.”

A sobering thought

via Billion Tonne Comet May Have Missed Earth By A Few Hundred Kilometres in 1883  – Technology Review.

[UPDATE]

Phil Plait, the badass astronomer behind the awesome Bad Astronomy blog has an insightful analysis here: Did a fragmenting comet nearly hit the Earth in 1883? Color me very skeptical

Mind you, Bonilla claimed to have seen these objects over the course of two days. That means they would’ve been stretched out along a path that was a million km long at least, yet so narrow that only one observatory on Earth saw them transit the Sun. That is highly unlikely.

Definitely worth reading and Phil Plait is doing a fantastic job to express something as complex as astronomy and physics in terms a math dropout like me can understand.