From a Wired.com article on the anniversary of the Tunguska event, this made me think:

 Quote:
Here's something to consider: In its 1966 edition, the Guinness Book of Records concluded that, based on the Earth's rotation, had the Tunguska meteorite struck 4 hours, 47 minutes later, it would have obliterated St. Petersburg, then the capital of imperial Russia. Given the events that would shortly torment that nation -- and all of Europe -- for the better part of the 20th century, one is left to wonder how history might have changed in those circumstances.