How does Father Christmas fit down a chimney and deliver gifts to millions of children in one night, without being heard? Dr Katy Sheen from the geography department at the University of Exeter theorised how last year.
• Santa Claus would have to travel at about 10 million kmh to every child expected to celebrate Christmas.
• He would have to do this in a span of 31 hours, taking into account time zones.
• According to relativity theory, at such high speeds he would shrink - or get thinner - in the direction he was travelling, enabling him to fit down chimneys.
• The high speeds would also make him move so fast that he would not be seen by the naked eye, rendering him unrecognisable to kids waiting up to see him.
• As Santa and his sleigh approach, the bells and his "ho, ho, ho" would get higher and higher in pitch, until they would be beyond human hearing range. (This is known as the Doppler effect and explains why children cannot hear him coming.)
• How does he reach these speeds? That part is magic!
Shelina Ajit Assomull