Earth as a Magnet

Introduction What do you think the world’s largest magnet looks like? Did you know that you are standing on it? The Earth is the largest magnet that we come in contact with. The magnet reaches from deep below the crust to miles above the atmosphere.

Earth as a Magnet Compasses were invented centuries ago, but no one knew why they always pointed where they did. Sir William Gilbert, English Physicist experimented with a compass and hypothesized that Earth behaved like a giant magnet. It turned out that he was right and the Earth had two magnetic poles, north and south with a magnetic field surrounding it.

Earth’s Core Scientists used to believe that Earth’s core contained magnetic material, but the core is too hot to support that theory. Earth’s innermost core is solid, but temperatures can be hotter than the surface of the sun which would disrupt and destroy magnets. Scientists now believe that the circulation of molten iron around the core causes the Earth to act like a magnet. Further experimentation and exploration is needed to prove this theory.

Diagram of Earth’s Core

Earth’s Magnetic Poles The Earth has two different types of poles: magnetic poles and geographical poles. These two poles are not in the same place. The magnetic poles are located where the magnetic force is the highest. The north geographic pole is located almost 775 miles away from the magnetic pole.

Magnetic Declination If you are using a compass you have to remember that the magnetic poles and geographical poles are different. Imagine a line drawn from you to the geographic north. Now imagine a line drawn from you to magnetic north. The angle between these two lines is known as magnetic declination. This is the north to which a compass points and depending on where you are the magnetic declination is different. The magnetic poles shift over time.

Earth’s Magnetic Field Materials can be made into magnets as long as there is a strong magnetic field present. The Earth has a very strong magnetic field surrounding it as you saw in a previous slide. The Earth can make very strong magnets out of ferromagnetic materials such as iron, nickel, and cobalt.

Magnet Maker Let’s say a piece of iron or iron ore is left somewhere for many years. Earth’s magnetic field can attract the domains to line up in one direction. This means that Earth’s magnetic field has turned it into a magnet. If the desk you are sitting at is metal or if the filing cabinets around the room are made of ferromagnetic material they are already trying to become magnets! (The process takes a long time…)

Earth’s Record The Earth’s mantle and core have large amounts of iron and sometimes this iron comes to the surface as lava. When this lava or magma hardens it keeps a record of which way the magnetic domain was. Scientists have discovered through this process that the magnetic poles have switched multiple times. Scientists are still researching how and why Earth’s magnetic field changes. Some believe that the current of the molten iron in the Earth’s core changes.

Magnetic Field Record

Magnetosphere As you have seen in previous slides Earth’s magnetic field extends into space. This field affects electrically charged particles in space and those particles also affect the magnetic field. There are two major regions known as the Van Allen belts which are named after the discovering scientist J.A. Van Allen. In these regions there are electrons and protons traveling at very high speeds.

Diagram of Magnetosphere

Solar Wind As you saw in the diagram solar winds are always moving from the sun towards our planet. Solar wind is a stream of charged particles moving at high speeds from the sun to the earth. These solar winds give the magnetosphere its shape and is constantly reshaping it as the Earth orbits the sun and rotates on its axis. Most particles from this wind cannot get through the Earth’s magnetic field, but some do manage to get through near the poles.

Auroras When these solar winds breach the magnetic field they react with the atmosphere. This causes a well known phenomenon known as auroras. Auroras are glowing regions of atmosphere caused by highly charge particles. Auroras in the Northern Hemisphere are known as Northern Lights or aurora borealis. Auroras in the Southern Hemisphere are known as Southern Lights or aurora australis.

Conclusion The Earth is very similar to a magnet with a north pole and a south pole. The Earth has two different types of poles: magnetic poles and geographical poles. The difference between the two poles is known as magnetic declination. The Earth can create magnets and leave records of its pole reversal. The Magnetosphere extends miles into the atmosphere and protects Earth from most solar winds.

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