An introduction to Earth's magnetic field: what it is, where it comes from and what it's used for.<br /><br />This is the first of three videos:<br />Magnetic field: an introduction<br />Magnetic field: why it matters: http://youtu.be/6vYzVdSxjUs<br />Magnetic field: learning more with Swarm http://youtu.be/Wn-BV9Zp8Pk
