The Santa questions start firing at you before your kids turn five. How does he speed around the world in a single night? How does he know what I want? Sure, you could deny Santa’s existence, but be ready for some tears.
The good news is, there are perfectly reasonable answers to the many questions relating to his annual mission. The bad news: The science involved is typically beyond the mental reach of the average six year old. Most graduate students can’t understand the specifics of wormhole formation. Second-graders? Forget it.