What are great circles?

A great circle is like the biggest possible loop you can draw around a ball, think of it as the path a toy car would take if it drove all the way around Earth without lifting its wheels.

Imagine you have a perfectly round orange. If you slice it with a knife from one side to the other, passing through the center, that’s a great circle. It's like the widest line you can draw on the orange, no matter how you turn the knife, this is always the biggest loop possible.

Now think of Earth as that orange. If you take a piece of string and stretch it tight around the globe so it goes through the center, that’s a great circle too. The equator is one example, it's like a big belt around Earth’s middle.

Another great circle would be any line that goes straight through the North Pole to the South Pole, like the path of a plane flying from one end of the world to the other.

When you travel along a great circle, you're taking the shortest path between two points on a sphere. So if you're drawing a map or figuring out how far it is from New York to London, following a great circle gives you the most direct route, just like cutting straight through an orange gives you the biggest slice!