The shortest route between Point A and Point B… Hey that’s not a straight line!

May 4, 2007

An excellent opportunity for you to merge Geography and Geometry in your lessons is to discuss Great Circles. Simply put great circles are circles that mark the shortest distance between two points along a circumference of a sphere (such as the Earth) . When trying to get from point A to point B on a sphere you need to take the curvature of the sphere into account in order to find the shortest path. This is done all the time in the airline industry to determine the shortest flight path. What it does do is distort the “straight line” when viewed on a flat map.

The web site Tall Eye can be a great tool to help clarify this concept. Tall Eye allows you to plot a straight line course between two points on the Earth. Basically it allows you to see what areas of the Earth you would pass through if you walked a straight line, in any direction, between two points. While this is sort of cool in and of itself, it becomes valuable to Geography and Geometry teachers when one looks at how the straight line gets represented on a flat map. It clearly is not straight. Any student using this web site probably will have the same reaction, Why? Your teachable moment has arrived.

Lets look at straight line due east from Massachusetts to Massachusetts.

Great Circle

If you want to see the full path here is the link.

This is a simple way to present a more complex issue in an engaging and interesting fashion using technology. Have your students examine how the circles change as you get closer to the equator or the poles. What happens to the curve as change the direction of your path? There are many opportunities for you to use Tall Eye to help your students make the connection between Geography and Geometry.

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