For navigational purposes, each great circle on the Earth has a length of ______?

The length of each great circle on the Earth is 21,600 nautical miles. This measurement is derived from the fact that the Earth’s circumference is approximately 24,901 miles. When converted to nautical miles—where one nautical mile is based on one minute of latitude—this results in a total of approximately 21,600 nautical miles along a great circle.

Understanding that a nautical mile is specifically tied to the geometry of the Earth, and is equivalent to one minute of arc, is crucial in navigation. This means that when navigating at sea, mariners often refer to distances in nautical miles rather than statute miles, as the former corresponds directly to latitude and longitude calculations.

Thus, recognizing that each great circle represents the shortest distance between two points on the surface of a sphere reinforces its significance in navigation, making it valuable for plotting efficient maritime routes. The other length options provided do not correspond accurately to the Earth’s dimensions in the context of navigational charts or distances used by seafarers.