When the star that we call our Sun condensed out of a swirling cloud of hot interstellar gas, some material remained in orbit around the newly forming star. That orbiting material consisted of hot chunks of rock and frozen liquids called "planetisimals". From these were gradually formed several (nine that we know of) planets including Earth. The planets - including Earth - still move in relatively stable orbits around the sun.Earth not only orbits the sun but spins on its own axis as it does so. At the equator the Earth is spinning on its axis at a speed of about 1,038 miles (1,670 kilometres) an hour. Earth's spin or rotation is a relic of its origin as a hot, spinning mass when it was first formed.Earth science or geology is the science of the Earth. It is an organized study and body of knowledge about mountains, plains and oceans; about the history of life on Earth; and about the succession of physical events that have been (or are still) part of this history.