Tonight's the night the magic happens. Old St Nick sets off from the North Pole and delivers presents to children all around the world. How does he do it?

On December 24, every year, Santa Claus piles his sleigh up with presents, he hitches Rudolph and his other reindeer up and heads off to deliver those gifts to every child in the world.

How?

JJ Eldridge, Associate Professor in Physics at the Faculty of Science, University of Auckland said if she was Santa, she would start with cloaking technology, which would explain why no one ever sees Santa dropping off the presents, and there is already a bit of this tech in development.

The ability to cover the whole world in one night gets trickier, but JJ said it is not outside the realms of possibility.

"One of the most difficult things about physics is you have to kind of throw out everything you understand from your own eyes and ears about how the world works," she said, "Because when we go down to the very small level, the quantum mechanics level, things get a bit strange."

Go to this episode on rnz.co.nz for more details