• Sara Thompson

Which Way Is North?

By Sara Thompson

Special to the Enterprise

Image of a globe
The Northern Hemisphere map of the Earth showing locations of True North (round dot) and Magnetic North (star-shaped dot); Image by Pearson Scott Foresman, from Wikimedia Commons.

Deep within our planet is solid, metal core composed primarily of iron and nickel. Surrounding the inner core is the outer core, a mass of the same metals in molten form, always in motion. It is the movement of this liquid metal that generates our planet’s magnetic field. The magnetic field extends out and surrounds our planet and helps protect us from particles generated from the sun. The point on the earth that the field extends out is called Magnetic North and is where our compass needles point to. The top of the world, where all the lines of longitude meet, is the Geographical, or True North. These two points are not in the same place and the difference between them is called Magnetic Declination.

Currently the difference between the Magnetic and Geographic North is about 500 kilometers. The point of Geographic North lies in the Arctic Ocean and is a fixed point that will never change. Arrows on maps and most GPS defaults will be pointing towards Geographic North. Magnetic North, however, is in the far northern part of Canada, and has been drifting towards Russia.

Magnetic Declination is different depending on where you are in the world. It is measured as the angled difference between Geographical and Magnetic North and can be anywhere from 0o to a 20o difference. Where the two North’s are the same is called the agonic line, and the difference is either East or West of the line. The Magnetic Declination in the Sacramento region is 15o, meaning a compass will point 15o off from where Geographical North is. Many compasses are able to adjust between the angles by rotating the compass face on a base.

Campers in this week’s Map It! Summer Science Camp learned about the difference between magnetic and true north and participated in an orienteering scavenger hunt with their compasses. They searched for nearby geocaches, made paper mâché globes, and made their own map of Mace Ranch Park.

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