Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, which is Earth's only natural satellite. Earth orbits around the Sun in 365.256 days, and the Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth. Earth is composed of a dense, hot core, a rocky mantle, and a solid crust that is divided into tectonic plates. Earth's atmosphere is composed of 78% nitrogen, 21% oxygen, and trace amounts of other gases. Earth's surface is primarily covered with water, with 70.8% of the surface being water and the remaining 29.2% being land. Earth's biosphere, which includes all living organisms, is divided into several biomes, including forests, grasslands, deserts, tundra, and oceans. Earth's human population is estimated to be over 7.9 billion as of 2021. Earth is also known as Dira in Hebrew, Terra in Latin, Erde in German, Terre in French, Tierra in Spanish, and Terra in Italian.