It was recently brought to the attention of us extragalactic astronomers that there was a launch of a NASA satellite called the Magnetospheric MultiScale (MMS) Mission. In addition to providing a new tongue twister for students, the goal of this research satellite is to study the general properties of magnetic fields.
Earth is the only rocky planet in our solar system surrounded by a magnetic field, which is thought to arise as a result of Earth having a central core partially composed of molten metal. As Earth rotates the metal sloshes around inside the core, and a bar magnet is established. There are north and south magnetic poles, and field lines which start at the north pole and extend to the south pole. This is all well-known to the average kid scout.
What might be less well known that the magnetic field is important to humans as it acts physically rather like a shield. Harmful cosmic rays hit the Earth every day. These microscopic bullets from space get caught by the magnetic field. The magnetic field makes them travel along the field lines like pearls on a string to the north and south poles, where the cosmic rays are deposited and strike the Earth at locations where the population density is lower.
While many cosmic rays get caught by the magnetic field shield, unfortunately some cosmic rays make it past the shield and hit Earth at lower latitudes. Although too small to see, some say that it is strikes by these cosmic ray bullets on humans that are responsible for causing certain cell mutations which lead to cancerous growth. It would seem about time to learn more about Earth's magnetic field which provides such an important protective function for life on Earth.
In addition, there are also magnetic fields measured around stars, entire galaxies, and even in-between galaxies. In such cases it is less obvious how such fields are generated, as there is no molten metal in stellar cores (too hot!), or around galaxies or in deep space. Magnetic fields on such large scales may be important for assisting the formation of galaxies such as our own Milky Way, by lowering the circular momentum enough to allow for gravitational collapse. By studying the magnetic field around Earth, the hope is that we will be able to extend and expand this knowledge to application over much of the universe. Go MMS!