Closest Comet to Earth

According to recorded history this was comet Lexell in 1770. But recently, scientists theorize that at least 2 comets have struck Earth. The one that killed off the mammoths around 13,000 BC and the one that caused the Flood.

"At first, the comet appeared to possibly be heading right for the red planet - or at least within range of the team of satellites in orbit. Siding Spring will sidle up to Mars at a distance of just 83,000 miles (132,000 km). To put that into perspective, the closest documented comet approach to Earth was 1.4 million miles (2.3 million km). On July 1, 1770, comet Lexell came as close to Earth as any comet in recorded history, and it was still six times further out than the Moon."

Read more at: [link to phys.org]

Seems like space is a dangerous place where comets can come in sizes not normally talked about and to places not normally dreamed. Time makes that possible for its about statistical extrapolation and less about biscuits and gravity.