ME; FIRST FACT. THE EARTH WAS ONCE BELIEVED TO BE THE CENTRE OF THE UNIVERSE. EARTH IS THE ONLY PLANET NOT NAMED FOR A MYTHOLOGICAL GOD OR GODDESS. THE GRAVITY BETWEEN THE EARTH AND THE MOON CAUSES THE TIDES ON EARTH. THE ROTATION OF THE EARTH IS GRADUALLY SLOWING DOWN. EARTH IS THE MOST DENSE PLANET IN THE SOLAR SYSTEM.