The Earth was created 4.54 billion years ago when part of the Sun's accretion disc agglomerated into a spherical body. At that time, shortly after the birth of the Sun itself, the solar system's matter was much more scattered around, in the form of asteroids and dust rather than planets. This "matter cloud" has been called a Bok globule, and these globules have been observed in other parts of the Galaxy. Scientists have determined the age of the Earth relatively precisely using isotope dating of the world's oldest rocks.
It is not known precisely what mechanism caused the precursor of the solar system, a gaseous nebulae, to form into the Sun and its attendant accretion disc.