James J Kolata - Elementary Cosmology: From Aristotles Universe to the Big Bang and Beyond

Elementary Cosmology:
From Aristotles Universe to
the Big Bang and Beyond

James J Kolata

University of Notre Dame, USA

Morgan & Claypool Publishers

Copyright 2015 Morgan & Claypool Publishers

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ISBN 978-1-6817-4100-0 (ebook)
ISBN 978-1-6817-4036-2 (print)
ISBN 978-1-6817-4228-1 (mobi)

DOI 10.1088/978-1-6817-4100-0

Version: 20151101

IOP Concise Physics
ISSN 2053-2571 (online)
ISSN 2054-7307 (print)

A Morgan & Claypool publication as part of IOP Concise Physics
Published by Morgan & Claypool Publishers, 40 Oak Drive, San Rafael, CA, 94903, USA

IOP Publishing, Temple Circus, Temple Way, Bristol BS1 6HG, UK

To my wife Ann who encouraged me throughout this book project, and to the many Notre Dame students whose questions and comments over the years contributed immensely to the development of the Elementary Cosmology course.

Cosmology is the study of the origin, size, and evolution of the entire Universe. Every culture has developed a cosmology, whether it be based on religious, philosophical, or scientific principles. In this book, the evolution of the scientific understanding of the Universe in the Western tradition is traced from the early Greek philosophers to the most modern 21st century view.

This book began as a series of lecture notes for a one-semester course at the University of Notre Dame called Elementary Cosmology. An elective for non-science majors, it was designed to acquaint the non-mathematically inclined student with the most important discoveries in cosmology up to the present day and how they have constantly altered our perceptions of the origin and structure of the Universe. It examined such questions as Where did the Universe come from?, Why do scientists now feel sure that its birth was in a great cosmic fireball called the Big Bang?, and Where did the Big Bang itself come from?. The emphasis was on class discussion of readings from science popularizations for the curious and intelligent layperson, focusing eventually on the many interesting and exciting new discoveries in cosmology in the late 20th and early 21st century.

After a brief introduction to the concept of the scientific method, which underpins all scientific approaches to the study of the Universe, the first part of the book describes the way in which detailed observations of the Universe, first with the naked eye and later with increasingly complex modern instruments, ultimately led to the development of the Big Bang theory which supplies the framework for our current understanding of cosmology. The key to this theory is the realization that our Universe, far from being static and eternal, has instead been expanding in size since its origin some 13.5 billion years ago. While the fact of this expansion was accepted rather soon after it was first proposed in the 1920s and 1930s, the more radical idea that the Universe had a birthday was more difficult for scientists to accept. It was only with the development of modern, satellite-based communication devices in the 1960s that instruments sensitive enough to detect the cosmic microwave background (CMB) were produced. It is now understood that the CMB consists of ancient light, emitted at a time near to the formation of the Universe. As such it is the smoking gun of the Big Bang and detailed studies of its properties have led to many interesting and fascinating new discoveries in cosmology.

The second part of the book traces the evolution of the Big Bang theory itself, including the very recent observation that the expansion of the Universe is itself accelerating with time. In addition, the contribution of modern physics to our understanding of the mechanism of the Big Bang is discussed and the state of the Universe at various eras throughout its history is described. Finally, some speculations beyond current knowledge that bear on cosmology are introduced and the implications for future developments in our understanding of the Universe are described.

The text contains many links to websites that clarify and extend the discussion. By following these links (some to images and videos), the reader can attain a much more in-depth understanding of many of the concepts introduced in this book. This is especially true for those seeking a more mathematical discussion of the topics, which is beyond the level of the current text.

I acknowledge with gratitude the assistance of Karen Donnison, and Jacky Mucklow at IOP Publishing in production of the manuscript into its final form.

James J Kolata

James J Kolata is an emeritus professor of physics at the University of Notre Dame in the USA and a Fellow of the American Physical Society. He is the author of over 250 research publications in nuclear physics.

IOP Concise Physics

Elementary Cosmology: From Aristotles Universe to the Big Bang and Beyond

James J Kolata

The scientific method is a procedure for obtaining knowledge about the Universe around us. It begins with the assumption that there is an objective reality that can be observed and measured, and provides a framework for systematizing and extending these observations. A key characteristic of the method is that it seeks to eliminate individual bias by insisting on reproducibility of results. In order to describe the method in more detail, it is necessary to define a number of terms, some of which have different meanings from the way they are understood in common usage. These are:

• Fact: The result of an experiment or observation. In the scientific context, facts are observations that have been repeatedly reproduced and confirmed so that they are regarded as true for all practical purposes. However it is important to recognize that truth in science is never final and facts accepted today may be changed or even discarded tomorrow. This is quite different from the common usage in which a fact is often assumed to be an immutable truth.