The Sun is surrounded by a network of invisible magnetic forces that help to form dangerous storms in space. However, the Sun appears inactive in the sky, just as a bar magnet sitting on a table seems inert. We can map out the magnetic field around a bar magnet by simply scattering iron filings around it and watch as they line up in a pattern of lines that trace the hidden forces at work. This experiment is easy enough to do at home, but how can we learn about fields on grander scales?