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"Mitton, Simon"
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The Big Bang versus the Steady State: Gamow, Hoyle and Ryle, rivals in cosmology
This account of the controversy concerning the Big Bang and Steady State theories contrasts the different approaches to science of George Gamow, Fred Hoyle and Martin Ryle. Einstein’s general relativity offered theoretical physicists an indispensable tool kit for making mathematical models of the Universe. Georges Lemaître made an astonishing impact in 1927 with his proposal that the expanding Universe started from a decaying super-radioactive primeval atom. Gamow refined Lemaître’s model by proposing that primordial nucleosynthesis in the early expanding Universe had formed the chemical elements. Hoyle, who by contrast had discovered the conditions under which stellar nucleosynthesis could occur via the evolution and explosion of massive stars, publicly dismissed Gamow’s cosmology as an unnecessary speculation. Hoyle, Hermann Bondi and Thomas Gold proposed the alternative steady state theory in 1948. In 1950 Ryle constructed the first radio telescope with the sensitivity to discriminate between the rival models of the Universe. Steady state cosmology survived Ryle’s first surveys of cosmic radio sources because Ryle’s data was inadequate. However results from the much improved Third and Fourth Cambridge Surveys demonstrated that our Universe had evolved. The Ryle-Hoyle debates became intensely passionate and personal. In 1965 the discovery of the cosmic microwave background radiation settled the argument in favour of the Lemaître Big Bang evolving Universe.
Journal Article
One hundred years of the cosmological constant: from “superfluous stunt” to dark energy
We present a centennial review of the history of the term known as the cosmological constant. First introduced to the general theory of relativity by Einstein in 1917 in order to describe a universe that was assumed to be static, the term fell from favour in the wake of the discovery of the expanding universe, only to make a dramatic return in recent times. We consider historical and philosophical aspects of the cosmological constant over four main epochs; (i) the use of the term in static cosmologies (both Newtonian and relativistic): (ii) the marginalization of the term following the discovery of cosmic expansion: (iii) the use of the term to address specific cosmic puzzles such as the timespan of expansion, the formation of galaxies and the redshifts of the quasars: (iv) the re-emergence of the term in today’s Λ-CDM cosmology. We find that the cosmological constant was never truly banished from theoretical models of the universe, but was marginalized by astronomers for reasons of convenience. We also find that the return of the term to the forefront of modern cosmology did not occur as an abrupt paradigm shift due to one particular set of observations, but as the result of a number of empirical advances such as the measurement of present cosmic expansion using the Hubble Space Telescope, the measurement of past expansion using type SN Ia supernovae as standard candles, and the measurement of perturbations in the cosmic microwave background by balloon and satellite. We give a brief overview of contemporary interpretations of the physics underlying the cosmic constant and conclude with a synopsis of the famous cosmological constant problem.
Journal Article
George Gamow and Ralph Alpher: a review of their cosmological collaboration as mentor and protégé 1942–1955
George Antonovich Gamow (1904–1968) and Ralph Asher Alpher (1921–2007) were associates from 1942 until 1968. In this paper, we examine an intense period of collaboration at George Washington University. Our inquiry pivots on a collection of 53 letters and postcards in the Library of Congress (LoC) that Alpher received from Gamow during his absences from Washington DC. In order to set our examination of the letters in their historical context, we present brief biographies of Gamow and Alpher, summarise the state that nuclear astrophysics had already reached by 1945, and examine the initial impact of the
αβγ
paper. We conducted detailed analysis of twenty of the LoC letters which documents successive attempts by Alpher and Gamow to address the deficiencies in their model of primordial element building by neutron-capture in the big bang. We give a detailed account of the interactions between Gamow writing from Los Alamos, New Mexico, and his two co-workers Alpher and Robert Herman in Washington DC. The correspondence brings their enthusiasm and commitment to life as they react to the advances and setbacks they encountered. Our narrative illustrates the remarkable partnership that Gamow and Alpher shared, a this was, infused with friendship and therein scientific discovery.
Journal Article
Einstein’s 1917 static model of the universe: a centennial review
We present a historical review of Einstein’s 1917 paper ‘Cosmological Considerations in the General Theory of Relativity’ to mark the centenary of a key work that set the foundations of modern cosmology. We find that the paper followed as a natural next step after Einstein’s development of the general theory of relativity and that the work offers many insights into his thoughts on relativity, astronomy and cosmology. Our review includes a description of the observational and theoretical background to the paper; a paragraph-by-paragraph guided tour of the work; a discussion of Einstein’s views of issues such as the relativity of inertia, the curvature of space and the cosmological constant. Particular attention is paid to little-known aspects of the paper such as Einstein’s failure to test his model against observation, his failure to consider the stability of the model and a mathematical oversight concerning his interpretation of the role of the cosmological constant. We recall the response of theorists and astronomers to Einstein’s cosmology in the context of the alternate models of the universe proposed by Willem de Sitter, Alexander Friedman and Georges Lemaître. Finally, we consider the relevance of the Einstein World in today’s ‘emergent’ cosmologies.
Journal Article
Interrogating the Legend of Einstein's “Biggest Blunder”
It is well known that, following the emergence of the first evidence for an expanding universe, Albert Einstein banished the cosmological constant term from his cosmology. Indeed, he is reputed to have labelled the term, originally introduced to the field equations of general relativity in 1917 in order to predict a static universe, his “biggest blunder.” However, serious doubts about this reported statement have been raised in recent years. We interrogate the legend of Einstein’s “biggest blunder” statement in the context of our recent studies of Einstein’s cosmology in his later years. We find that the remark is highly compatible with Einstein’s cosmic models of the 1930s, with his later writings on cosmology, and with independent reports by at least three physicists. We conclude that there is little doubt that Einstein came to view the introduction of the cosmological constant term as a serious error and that he very likely labelled the term his “biggest blunder” on at least one occasion. This finding may be of some relevance for those theoreticians today who seek to describe the recently discovered acceleration in cosmic expansion without the use of a cosmological constant term.
Journal Article
Historical and philosophical reflections on the Einstein-de Sitter model
We present some historical and philosophical reflections on the paper “On the Relation Between the Expansion and the Mean Density of the Universe”, published by Albert Einstein and Willem de Sitter in 1932. In this famous work, Einstein and de Sitter considered a relativistic model of the expanding universe with both the cosmological constant and the curvature of space set to zero. Although the Einstein-deSitter model went on to serve as a standard model in ‘big bang’ cosmology for many years, we note that the authors do not explicitly consider the evolution of the cosmos in the paper. Indeed, the mathematics of the article are quite puzzling to modern eyes. We consider claims that the paper was neither original nor important; we find that, by providing the first specific analysis of the case of a dynamic cosmology without a cosmological constant or spatial curvature, the authors delivered a unique, simple model with a straightforward relation between cosmic expansion and the mean density of matter that set an important benchmark for both theorists and observers. We consider some philosophical aspects of the model and provide a brief review of its use as a standard ‘big bang’ model over much of the 20th century.
Journal Article
Astroparticle physics and cosmology
Astroparticle physics is an interdisciplinary field that explores the connections between the physics of elementary particles and the large-scale properties of the universe. Particle physicists have developed a standard model to describe the properties of matter in the quantum world. This model explains the bewildering array of particles in terms of constructs made from two or three quarks. Quarks, leptons, and three of the fundamental forces of physics are the main components of this standard model. Cosmologists have also developed a standard model to describe the bulk properties of the universe. In this new framework, ordinary matter, such as stars and galaxies, makes up only around 4% of the material universe. The bulk of the universe is dark matter (roughly 23%) and dark energy (about 73%). This dark energy drives an acceleration that means that the expanding universe will grow ever larger. String theory, in which the universe has several invisible dimensions, might offer an opportunity to unite the quantum description of the particle world with the gravitational properties of the large-scale universe.
Journal Article
Einstein’s steady-state theory: an abandoned model of the cosmos
We present a translation and analysis of an unpublished manuscript by Albert Einstein in which he attempted to construct a ‘steady-state’ model of the universe. The manuscript, which appears to have been written in early 1931, demonstrates that Einstein once explored a cosmic model in which the mean density of matter in an expanding universe is maintained constant by the continuous formation of matter from empty space. This model is very different to previously known Einsteinian models of the cosmos (both static and dynamic) but anticipates the later steady-state cosmology of Hoyle, Bondi and Gold in some ways. We find that Einstein’s steady-state model contains a fundamental flaw and suggest that it was abandoned for this reason. We also suggest that he declined to explore a more sophisticated version because he found such theories rather contrived. The manuscript is of historical interest because it reveals that Einstein debated between steady-state and evolving models of the cosmos decades before a similar debate took place in the cosmological community.
Journal Article
Einstein’s cosmology review of 1933: a new perspective on the Einstein-de Sitter model of the cosmos
We present a first English translation and analysis of a little-known review of relativistic cosmology written by Albert Einstein in late 1932. The article, which was published in 1933 in a book of Einstein papers translated into French, contains a substantial review of static and dynamic relativistic models of the cosmos, culminating in a discussion of the Einstein-de Sitter model. The article offers a valuable contemporaneous insight into Einstein’s cosmology in the early 1930s and confirms that his interest lay in the development of the simplest model of the cosmos that could account for observation. The article also confirms that Einstein did not believe that simplified relativistic models could give an accurate description of the early universe.
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