The Great Circle of the World

By Phin Upham

For any two points on opposite sides of a sphere, there is a “Riemannian” or “Great” circle that perfectly bisects the sphere at those points. Of course, this also means that the diameter of the circle that bisects the sphere is equivalent to the size of the sphere itself. In plain terms, it is the largest possible circle that one can draw around a sphere.

One way of thinking about the Great Circle of Earth is the equator, which bisects the planet. Although, the Earth is not a perfect circle. It does maintain the appearance of one, and any Meridian on the planet is part of a potential Great circle.

The Great circle is useful for a number of ideas concerning our planet. For one, it helps us understand the foundations of longitude and latitude, and helps us define the circular nature of our planet. The lines tend to get smaller as they get closer to the poles.

Pilots also use the Great circle to help plot flight paths that take them around the world. The shortest path between two points on a sphere is always going to be a part of the Great circle, so it’s important to understand some basic geometry when plotting airplane routes. Although, the Great circle is not the end all in guidance systems. Pilots encounter many different weather patterns along the way that can cause them to deviate from the line that takes them through the Great circle of Earth.

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About the Author: Phin Upham is an investor at a family office/ hedgefund, where he focuses on special situation illiquid investing. Before this position, Phin Upham was working at Morgan Stanley in the Media & Technology group. You may contact Phin on his Phin Upham website or Twitter page.