Earth’s orbit around the Sun is not circular, but an ellipse. The perimeter of Earth’s orbit is roughly 584 million miles (940 million km).

In terms of security measures, there is a steel, anti-climb fence around the perimeter of the Ellipse. The only security checkpoint for the event is located at 17th Street NW and Constitution Ave.

After 9/11, security design in major public spaces took on a new significance, and at President’s Park South—a large ellipse forming a public extension of the White House’s front lawn—this ...