# The Earth's EM Field and Compasses

## What is the Earth's Magnetic Field?

The Electromagnetic, or EM field, is the Earth's natural protection against the Sun's harmful, hot rays. The Magnetic field starts at the Earth's outer core, and meets the solar wind in the atmosphere. The purpose of the Magnetic Field is to protect the Earth's inhabitants from UV rays. Without the Earth's Magnetic Field, there would be no atmosphere and no water. Without these things, Earth would not have life.

## What is a compass, and how does the Magnetic Field Affect compasses?

A compass is a small and simple gadget that helps you to tell you where you are on the Earth using the cardinal directions North, South, East, and West. You can tell this using a compass because the compass's red needle will always point North. The Magnetic Field affects compasses because the Magnetic Field causes the Earth to have two magnetized poles- The North Pole and the South Pole- and because of this, the compass relies on the North Pole to work.

## Parts of the Compass

The bottom piece of clear plastic in which you will hold the compass on is called the base plate. The big arrow that is outside of the circle is called the Direction of Travel arrow, and the two lines that are in the circle is the Gate. The circle piece of metal that spins is called the 360 degree dial. The needle that resides in the 360 degree dial is the needle that points North and South. The red part of the arrow is typically red colored, and the South white or black. The 360 degree dial is as you would expect it to be; it has 360 numbers- also called degrees- on it.

## Step Four

• To accurately follow the direction of travel arrow, look down at the arrow, then focus on a distant object like a tree, telephone pole, or other landmark, and use this as a guide.