## Mysterious magnetism: From the Earth to the stars

We've known for centuries that compass needles point North, but why they do so is still a mystery. It's down to the Earth's magnetic field, of course, but exactly where this field comes from and how it behaves still isn't properly understood. The same goes for the magnetic fields of other planets, the Sun, and other stars further afield. Experts from around the world are currently gathered together for a research programme about the topic at the Isaac Newton Institute for Mathematical Sciences (INI) in Cambridge, hoping to lift the magnetic mystery.

This collection of articles explores what exactly is going on at the research programme and provides some background reading.

Why is the Earth a magnet? — Here's a brief introduction to the mechanism scientists believe creates the Earth's magnetic field, as well as those of other planets and stars. They all act like giant dynamos.

Mysterious magnetism — Many questions are still open, however. This article looks into them, and why they are so hard to answer.

Maths in a minute: The Navier-Stokes equations — The Earth's magnetic field is believed to be generated by a fluid moving around in its core. This is why the Navier-Stokes equations, which describe the behaviour of fluids, are important in understanding the magnetic field.

Maxwell's equations and the secrets of nature — Where magnets are involved, Maxwell's equation of electromagnetism always have a part to play. Here's a look at the equations and their role in physics.

What are liquid metal batteries? — The theory that explores the magnetic fields of planets and stars can also be used to understand liquid metal batteries. In this podcast we talk to Donald Sadoway about what liquid metal batteries are and why they hold much hope in our move to renewables.

*We produced this collection of content as part of our collaboration with the Isaac Newton Institute for Mathematical Sciences (INI), an international research centre and our neighbour here on the University of Cambridge's maths campus. INI attracts leading mathematical scientists from all over the world, and is open to all. Visit www.newton.ac.uk to find out more.*