Download Earth as a Magnet

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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