Earth is the third planet from the Sun and the only object in the Universe known to harbor life. According toradiometric dating and other sources of evidence, Earth formed over 4 billion years ago.[24][25][26] Earth's gravityinteracts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times.