Even these simple examples show that a magnetic field causes movement or orientation in a particular direction. This preferred direction manifests itself as 'field lines', and although magnetic fields are invisible to our eyes, their effects can be observed in many different environments beyond our world. They play an important part in shaping the universe – from the local scale of the solar system, to galaxies and beyond.
Galactic magnetism
This bewitching image shows magnetic fields on a galactic scale – it's a side-on view of the plane of our galaxy, the Milky Way, and shows how the galaxy's magnetic field in its plane (near-horizontal field lines in the image) interacts with that of the surrounding interstellar dust (a more turbulent pattern of field lines above and below the galactic plane).
Observations in both our own and other spiral galaxies have shown that the magnetic field follows the spiral pattern, as you can see in this image. The field itself is pretty weak at this scale, only a few millionths of the Earth's. Nevertheless, it affects a huge amount of matter and it is believed to play an important part in galaxy formation, by squeezing the interstellar gas that is the raw material for star formation in a particular direction, and feeding it towards the centre of the galaxy, where the steady flow of incoming gas results in a high rate of star production.
Nearer to home, our Sun has a strong magnetic field, in places 5000 time greater than the Earth's. Over a cycle of around 11 years the solar magnetic field repeatedly forms increasingly complicated and continually moving loops and twists on its surface and interior. This image of the Sun's surface superimposed with modelled magnetic field lines shows just how complicated the magnetic structure there can become. Perhaps the most dramatic and energetic results of the convoluted solar magnetism are the massive explosions of solar plasma, known as 'coronal mass eruptions' (CME) that occur when field lines snap together and apart. These events release huge amounts of charged particles into space, sometimes heading directly for our home planet.
Luckily for us the Earth is itself is a giant magnet, with magnetic field lines looping round over the surface between the north and south poles. This 'magnetosphere' forms a protective shield that deflects most incoming charged matter such as CMEs and the more constant 'solar wind', enabling the preservation of our atmosphere – and ultimately the development of life on Earth.
There are still many questions about the causes and effects of magnetic fields in space, particularly on a large scale of galaxies and bigger. Their role in the early stages of the development of the universe is poorly understood and is open to a lot of debate.
Radio telescopes are particularly well-suited to investigating magnetic fields in space, so there are high hopes that the new 'Square Kilometer Array' telescope (SKA), which will be much more sensitive than current radio telescopes and is expected to start producing science results in 2020, will help to shed some light on some of these unanswered questions.
1. ESA/Planck Collaboration. Acknowledgment: M.-A. Miville-Deschênes, CNRS – Institut d’Astrophysique Spatiale, Université Paris-XI, Orsay, France
2. MPIfR Bonn
3. NASA/SDO/LMSAL