Surface Area and Volume of a Sphere Essential Question: How to find the surface area and volume of a sphere? Sphere – set of all points in space equidistant from a given point called center. Radius – a segment that has one endpoint at the center and the other endpoint on the sphere. Diameter – a segment passing through the center with endpoints on the sphere. Great Circle – if the center of the circle is also the center of the sphere. Circumference – the circumference of a great circle. Two Hemisphere – created by the great circle