In fact, for a circle the size of the Earth, with a circumference of 40,075 kilometres, the difference between the perimeter of the inscribed megagon and the circumference of the circle comes to less than 1/16 millimeters.
In fact, for a circle the size of the Earth, with a circumference of 40,075 kilometres, so one edge of a megagon the size of the earth would be about 40 meters long. The difference between the perimeter of the inscribed megagon and the circumference of the circle comes to less than 1/16 millimeters.