MAGIC, SCIENCE & TECHNOLOGY

Does Santa have to obey the laws of physics?

Often, people complain about their jobs and how hard they work. Not us. We love our job as physicists.

Our job is to develop new technologies that accelerate particles like electrons, making them travel extraordinarily fast using incredibly powerful microwaves.

But spare a thought for those with tougher jobs, like Santa.

Almost a quarter of the world’s population are children living in remote areas. Now think of Santa, determined to reach every one of them in a single night with a special gift.

Santa needs to go very, very fast

To reach all these children, Santa and his helpers would need to travel incredibly quickly.

However, as theoretical physicist Albert Einstein predicted, there’s a universal speed limit: the speed of light, which is nearly one billion kilometres per hour. 

At the University of Melbourne’s XLAB, we’re developing a prototype for the next generation of accelerators – ones that can accelerate electrons to 99.99 per cent of the speed of light in just 20 centimetres.

This got us thinking: could our work help Santa reach all the world’s children in one day?

Let’s consider a ‘gedankenexperiment’, (which is German for a ‘thought experiment’).

Let's imagine Santa travelling from the North Pole to Nairobi, Kenya – a distance of about 10,000 kilometres.

Our goal: to get Santa there instantaneously, just as a beam of light does.

Picture Santa. He’s a fit 80 kilograms, ready to deliver 300 presents to just some of the kids in Nairobi, each weighing one  kilogram, in his electric-powered, carbon-fibre sleigh weighing 100 kilograms. 

All together, that’s a 480 kilogram payload.

Arts & Culture

The weird world of Christmas traditions

But there’s a catch.

As objects speed up, they gain relativistic mass – so they get heavier. Getting Santa’s sleigh up to 99 per cent of the speed of light would make it unimaginably heavy, requiring more than AUD$100 billion worth of electricity per trip. 

Travelling at the speed of light

What if Santa travelled slower, say at 100,000 kilometres per hour?

This speed would still require about AUD$18,500 of electricity per trip (of course, Santa’s sleigh is equipped with super-efficient solar panels tracking the sun) and take around 12 minutes per round trip. 

Let's work on the basis that Nairobi's population sits at around 5.1 million people. Around 34 per cent of them are children.

So to deliver presents to those 1.7 million kids means 5,780 trips with 300 presents on each trip. 

And that's for just one capital city in the world. So Santa needs to delegate.

With 27,778 helpers, the Santa team might just reach all the children in the world for under a billion dollars. This would mean each helper would need to do 240 trips independent of Santa – which is just good work practice.

The real challenge

Not all cultures celebrate Christmas.

More than a billion children around the world belong to traditions that don’t include receiving gifts from Santa.

But even among those who do, modern supply chains already enable remarkable feats.

For instance, Australia Post delivered nearly 100 million parcels in November and December last year alone.

But while logistics have advanced, the reality is that many of the world’s children won’t receive gifts.

Take Kibera and Mukuru, the largest urban slums in Kenya, where families survive on just a few dollars a day. Here, poverty – not tradition or logistics – is the barrier to joy.

Arts & Culture

‘Tis the season to celebrate Australia’s diversity

A gift that travels at the speed of light

Nairobi, Kenya’s capital, is unique for having a national park within its city limits, where the skyline is visible alongside wildlife.

But nearby Kibera reveals stark contrasts. Despite pervasive poverty, it’s a hub of resilience and innovation. 

One example of this is M-Pesa, a mobile money transfer service that allows people to send, receive and store money using mobile phones without traditional bank accounts.  

Opening a bank account often requires documents like proof of address, tax identification, and formal employment, which many residents in Kibera do not have.

M-Pesa requires only a valid ID and a mobile number.

This ingenuity underscores a powerful truth: there is a type of Christmas gift that could reach every child – a message of hope.

Radio waves and fibre-optic cables can carry a message at the speed of light, reaching every corner of the earth in less than 150 milliseconds.

A different kind of gift

While Santa may not need to bend the laws of physics, initiatives like the Ruben Centre and GiveDirectly can send impactful gifts to places like Kibera, using technology to reduce poverty, improve education and foster gender equality.

Meanwhile, our research at XLAB focuses on creating compact, efficient accelerators that could one day help treat cancer and other illnesses – a different kind of gift, but one with the power to change lives.

This Christmas, let’s combine imagination with action and bring light to all corners of the world.

And finally, for those of you keen to work out just how long it might take Santa to get to you and just how much energy is needed - here's a formula you can use to work it out for yourself: