NASA's 10 interesting facts about Earth

Earth is not flat, but it's not perfectly round either

Earth has never been perfectly round. The planet bulges around the equator by an extra 0.3 percent as a result of the fact that it rotates about its axis. Earth's diameter from North to South Pole is 12,714 kilometers (7,900 miles), while through the equator it is 12,756 kilometers (7,926 miles). The difference — 42.78 kilometers (26.58 miles) — is about 1/300th the diameter of Earth. This variation is too tiny to be seen in pictures of Earth from space, so the planet appears round to the human eye. Recent research from NASA's Jet Propulsion Laboratory suggests that melting glaciers are causing Earth's waistline to spread.