Over a series of posts I’d like to talk about lots of different aspects of this Natural force of Nature. From Geomagnetism to the Magnetosphere and from historic Navigational compasses to Magneto-reception in animals. But first I’d like to talk about the biggest magnet on earth : Planet Earth.
The earths North and South poles exist as a result of molten iron swirling miles beneath our feet. This liquid outer core at the centre of the earth is very active and flows in random patterns a bit like our weather. What generates this continuous movement, is the spin of the earth in space, which is 1000 miles per hour at the equator. Because of the spinning, a motor like effect is produced and in turn electrical currents are generated by the swirling iron. It’s these electrical currents which are responsible for creating the magnetic fields which polarise the Earth into a giant magnet with a North and a South pole.
More interestingly the North and South poles are constantly moving and we have to make an adjustment when using a map (which has a fixed north) with a compass (which follows the moving magnetic North). Here’s a link which explains this magnetic declination : http://www.magnetic-declination.com/what-is-magnetic-declination.php
NOAA has a very cool website about declination and this page shows where the north pole has moved over the last 400 years which was painstakingly generated from shipping logs collected from hundreds of historic journeys. This illustration shows the movement of magnetic north over the last 100 years. https://maps.ngdc.noaa.gov/viewers/historical_declination/
As well as orienting the earth’s magnetic field lines from north to south, the magnetic field also extends out beyond the earths atmosphere creating the Magnetosphere. Without the Magnetosphere, life on earth wouldn’t have evolved as we know it today because it shields us from the suns harmful radiation as this illustration shows.
This is also the reason we get the Northern Lights, more on this in the next post. I’ll leave you with this rather understated quote:
“I happen to have discovered a direct relation between magnetism and light, also electricity and light, and the field it opens is so large and I think rich.” — Michael Faraday (1899)