Brian Cox: Can Santa travel faster than the speed of light?

In this bedtime story the professor explains how Father Christmas can deliver presents with time to spare!


It was mid-September at the North Pole. The long arctic twilight faded into a five-month night. For the man dressed in red the vanishing sun signalled the beginning of his busy time.


On Christmas Eve he’d be called upon to visit over two billion children scattered around a planet with a surface area of 500 million square kilometers. But if space and time were constructed as Einstein proposed in his 1905 Special Theory of Relativity, then this would be impossible. This amused the man because he appreciated the profound beauty of Einstein’s work.

He remembered reading a paper entitled On the Electro-dynamics of Moving Bodies in which Einstein explained that nothing in the universe could travel faster than 300,000 kilometres per second – the speed of light.

This speed limit was woven into the fabric of the universe. If exceeded, cause and effect could be swapped around. The man in red would be able to deliver presents to children before they’d even sat down to pen their letters.

Now, over 100 years later, men had built a machine to create a beam of subatomic particles called neutrinos, and fire it through the Earth from Geneva to Rome. To their astonishment, those tiny particles appeared to make the trip faster than a light beam.

If shown to be correct, this would mean that E would no longer equal mc2, and perhaps journeys through space and time might become possible. Perhaps a man in red could visit two billion children in one night.

The man walked, still smiling, into a cave of ice, filled with boxes of all shapes and sizes.

“Neutrinos,” he said, patting a reindeer. There was pride in his voice; surprise at the progress of his children. “They are so eager to dismiss the magic in this universe, and yet so adept at exploring its beauty.”

He turned, smiling as he picked up a box wrapped in shining paper and imagined the reflected light dancing in excited eyes on Christmas morning. “Perhaps they’ll rename them Santa particles.”

Brian Cox hosts A Night with the Stars tonight at 9pm on BBC2 and BBC HD


This is an edited version of an article from the issue of Radio Times magazine that went on sale 7 December 2011.