The spots on the surface on the sun come and go with an 11-year periodicity known as the solar cycle. The solar cycle is driven by the solar dynamo, which is an interplay between magnetic fields, convection and rotation. However, our understanding of the physics underlying the solar dynamo is far from complete. One example is the so-called Maunder Minimum, a period in the 17th century, where spots almost disappeared from the surface of the sun for a period of over 50 years.