Whew - Now we know why Christmas only comes once a year - Santa needs that much time to recover!
From "Ask Me Anything" by Marg Meikle
A scientist named Roger Highfield wrote a book called, "The Physics of Christmas" ...figured out the following: Figuring on 2.5 children per household, Santa must make 842 million stops on Christmas Eve, travelling 355 million kilometres. Working with time zones and travelling against the earth's rotation, Santa actually has 48 hours to make his rounds – a little over 1/5000 of a second to reach each house and deliver the presents.
Now you know why it's so hard to see him!