Final answer:
A circle on Earth's surface with the Earth's center and radius is known as a great circle, such as the equator or any meridian passing through the poles.
Step-by-step explanation:
A circle on the surface of the earth whose center and radius are that of the Earth itself is known as a great circle. A great circle is the biggest circle that can be drawn on a sphere. On Earth, the equator is an example of a great circle. Other great circles can be formed by lines passing through the North and South Poles, which are known as meridians. These meridians are perpendicular to the equator and cross it at right angles. The significance of great circles lies in their use in navigation, as they represent the shortest path between two points on the surface of a sphere, such as the Earth.