Cosmogony

Cosmogony, the study of the origin and development of the universe as a whole and of the individual bodies that compose it. Since cosmogony attempts to deal with creation, cosmogonies of the past have been a part of religion or mythology. Modern cosmogony forms part of scientific cosmology, the study of all aspects of the large-scale physical universeits contents and organization as well as its history.

An attempt to explain the origin of the solar system by natural rather than supernatural processes was first made by Emanuel Swedenborg and Immanuel Kant in the mid-1700's. Their theories were very like the nebular hypothesis put forward in 1796 by Pierre Simon de Laplace.

The nebular hypothesis and its successors, the planetesimal hypothesis (by F. R. Moulton and T. C. Chamberlin, about 1905) and the tidal theory (by J. H. Jeans, about 1918), were discarded in favor of a theory of turbulent condensation. This theory, first proposed by the German physicist Carl von Weizscker in the 1940's, supposes that the newly formed sun was surrounded by a loosely knit, slowly rotating shell of matter as large as the present planetary system. The heavier materials making up this shell eventually accumulated as planets in pockets between the eddies within the churning shell. Such a theory seems to explain why the planes of the other planets' orbits nearly coincide with that of the earth's orbit and suggests why the planets are spaced from the sun as they are. Another theory, based in part on evidence from manned lunar exploration, states that the planets were formed cold in a process called accretion. This theory is explained in the article EARTH, subtitle The Earth's History.

The most widely accepted theory of the beginning of the universe itself is called the Big Bang Theory. According to this theory the universe came into being at a single point some 10 to 20 billion years ago. An alternate theory, the Steady State Theory, holds that the universe had no beginning and that the universe is much the same now as it always has been.