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Cosmological Theories in History

Dominant scientists and critical turning points in the
history of cosmology

Citation Information

Allan, Leslie 2015. Cosmological Theories in History, URL = <http://www.rationalrealm.com/science/physics/cosmological-theories-history.html>.

Nicolaus Copernicus portrait from Town Hall in Thorn/Torun - 1580

Since its birth in the modern scientific era, the science of cosmology has progressed through a number of phases. Each phase saw a radical shift in thinking as new experimental methods and powerful mathematics were applied to the latest novel insights. Below is a summary of the critical turning points in the history of cosmology.

Copernican Heliocentricism

In the mid-16th Century, Nicolaus Copernicus challenged the Ptolemaic view that dominated Europe for centuries. This was the view that the earth is at the centre of the universe, with the sun, the planets and the stars orbiting in perfect spheres. The widespread adoption of Copernicus' idea of a heliocentric system in which all celestial bodies orbited the sun led to what is termed the 'Copernican Revolution'.

Cartesian Vortices

René Descartes, the French philosopher writing in the mid-17th Century, proposed a model of the universe that was both infinite and static. In this universe, space was filled with ethereal matter that swirled around in large vortices and contributed to the attraction effects of matter that we see.

Static Universe

Some years later, Isaac Newton, although he agreed with Descartes static, infinite universe, diverged by postulating a non-mechanical explanation for the attraction between bodies. He also thought that matter was distributed uniformly throughout the universe, but was not stable.

Nebular Hypothesis

In the mid-18th Century, Immanuel Kant and Pierre-Simon Laplace developed independently the hypothesis that all of space is filled with fine matter. The attractive force between particles is counterbalanced by a repulsive force that causes matter to whirl in vortices. These swirling vortices are what result in planets and stars. What became known as the Kant-Laplace Nebular Hypothesis is one of the very first attempts at a scientific explanation of the origin of our universe.

Einsteinian Relativity

Albert Einstein, working in the early years of the 20th Century, believed, like Newton, that the universe is both static and dynamically stable. He precipitated another scientific revolution by showing how the three dimensions of space and the one dimension of time were inextricably intertwined and how gravity is an effect of the bending of space by bodies with mass. Controversially, he added a cosmological constant to his relativity equations to account for the observation that the universe is not contracting in on itself.

The Big Bang

Georges Lemaître and Alexander Friedmann, building on the work of Einstein, developed the first Big Bang models of the origin of the universe. On these models, the universe began expanding some 14 billion years ago from a singularity; an infinitely tiny and infinitely dense point. Applying Einstein's general relativity equations and depending on the amount of mass in the universe, the expanding universe could have a positive curvature (spherical space) or a negative curvature (hyperbolic space).

Oscillating Universe

The model of an oscillating universe results from a universe in which its total mass is greater than a critical amount. In this universe, space has a positive curvature, with matter expanding for a time before collapsing under its own weight, in a never-ending cycle of expansion and contraction. This was the model preferred by Einstein in his later years.

Steady State Universe

Fred Hoyle proposed this view in the middle of the 20th Century in opposition to the standard Big Bang theory. It was also championed by Thomas Gold and Hermann Bondi. On this view, the universe is continually expanding without a corresponding decrease in its density. Hoyle argued that the density of the universe remained constant because of the addition of matter that counterbalances the expansion.

Inflationary Universe

Since 1980, variations to the Big Bang theory have been proposed by physicists such as Alan Guth, Paul Steinhardt and Neil Turok. These modifications, designed to overcome some anomalies with the standard Big Bang model, allow for a period of very rapid expansion in the early universe. Further applications of string theory and branes to the idea of an early period of period of inflation lead to a cyclic universe in which the universe continually expands and contracts.

The Multiverse

Andrei Linde further modified the inflationary hypothesis to propose periods of eternal inflation. On this view, our universe is but one 'bubble' universe comprising a multiverse of many such bubble universes. Each bubble universe is the result of quantum fluctuations in the vacuum of space.

Copyright © 2015

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