Now imagine the earth as a large circle with the cities of Syene and Alexandria lying on the circle. They can be represented by two points separated by a distance of 496 miles. The 496 miles is the measure of the arc length from one point to the other on the circle. Go ahead and sketch this picture with Someone directly at the top of the circle and Alexandria a little to the right of Syene. Now draw a line from the center of the circle straight through Syene and another from the center through Alexandria. The line through Syene points directly to the sun at noon of summer solstice. The line through Alexandria represents the stick Eratosthenes used to calculate the sun's rays. This stick and its shadow form two sides of a right triangle whose hypotenuse is parallel to the sun's rays. The shadow of the stick forms the base of this right triangle. We know the top angle of the triangle is 7 degrees and 12 minutes based on the calculation of Eratosthenes.