Brian Cox on The Entire Universe, the science of Christmas – and why he’s wearing a red dress

The physics whiz offers some clever clogs answers to your most burning festive questions


First things first – you’re wearing a red dress and Eric Idle is putting make-up on you. Why?


It’s an illustration of the “many worlds” interpretation of quantum mechanics, which says that everything that can happen does happen. In other words, there is an infinite number of universes. So in one universe I might be Professor Brian Cox. And in another I’m Brian Cox wearing a nice off-the- shoulder red dress – which explains why I’m playing a part in Eric Idle’s science musical, The Entire Universe. 

Proper physics now. How does Santa deliver all those billions of presents around the world and still get home in time for breakfast?

It’s down to Einstein’s theory of special relativity, which tells you that the rate at which time passes is personal to you. So if someone moves very, very fast their clock runs more slowly than the rest of ours. Therefore, if you see Santa flying from house to house at 99.999999 per cent of the speed of light, time passes 7,000 times more slowly for him than for you. It may sound nonsense, but it’s real. 


Can science help me avoid a hangover?

Yes it can. Science is a method of clear thinking. If you clearly think about the best way to avoid a hangover, the answer is: don’t drink! 

What’s the most environmentally sound way of getting presents? Internet or one-horse open sleigh?

A one-horse open sleigh. The horse has an output of one horsepower. And a 1hp delivery has less impact on the environment than a 500hp delivery van.

A turkey and a goose are cooking in the same oven. How will that affect the cooking time?

It depends on the mass of the turkey and goose, the initial temperature of the meat and whether you’ve got a fan oven. It’s all about non-equilibrium thermodynamics, and in non-equilibrium thermodynamics, there’s no such thing as a simple question. That’s a motto I live by. 


The Entire Universe airs on Boxing Day at 9.30pm on BBC2