It's one of the biggest mysteries in the world, just how does one man and his reindeer travel all around the world delivering presents to lucky boys and girls??

Well, tomorrow night, one man will do just that. His name is Santa and he'll be bringing joy to billions in a matter of hours.

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But how does he do it?

Barry Fitzgerald is a scientist who has explored a whole manner of things from 'How to Build an Ironman Suit' to the science of superheroes.

So safe to say, he knows his stuff.

This morning, he joined Dermot and Dave to reveal the secret science of Santa Claus and it's every bit as incredible as you might imagine.

And of course, as we all look to mind the environment, Barry confirms that Santa is very much eco-friendly.

So get your mince pies and carrots for the reindeer ready, they've a busy night ahead.