The Origin of the Earth

The question of the origin of the blue planet pictured in figure 1 is related to other questions about our beginnings. These include the origin of the universe, the evolution of galaxies and stars, the origin of life and the ascent of humankind. In the late 1700s both Pierre‐Simon Laplace and Immanuel Kant suggested that Earth and the other planets in the solar system had condensed from a flattened nebular disk surrounding the Sun. Since these astute hypotheses were suggested, a series of well‐known physical scientists including James Jeans, Gerald Kuiper and Harold Urey have developed a now widely accepted theory of the accretion of the Earth and planets. Their theory, which I describe below, was based on telescopic observations of the solar system,theoretical calculations and the study of meteorites. Now referred to as the Schmidt theory (after Otto Yu. Schmidt of the Institute of the Earth, Moscow), it explains the formation of the planets as resulting from the accretion of already solid bodies.