John Gribbin - Einsteins Masterwork: 1915 and the General Theory of Relativity

Einsteins
Masterwork

1915 and the General Theory
of Relativity

JOHN GRIBBIN
with MARY GRIBBIN

PEGASUS BOOKS

NEW YORK LONDON

EINSTEINS MASTERWORK

Pegasus Books Ltd

148 West 37th Street, 13th Floor

New York, NY 10018

Copyright 2016 by John Gribbin

First Pegasus Books hardcover edition September 2016

All rights reserved. No part of this book may be reproduced in
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ISBN: 978-1-68177-212-7

ISBN: 978-1-68177-265-3 (e-book)

Distributed by W. W. Norton & Company, Inc.

Most of these books are accessible at about the level of the present volume but go into more detail about Einsteins life or work. Titles marked with an asterisk require a little more scientific background. Quotes in the text, unless otherwise indicated, are from the collected works or the Princeton archive. See The Collected Papers of Albert Einstein, volumes 110, published by Princeton University Press between 1987 and 2006. These take the story up to 1920, covering the major part of the story told in this book.

Amir Aczel, Gods Equation, New York: Random House, 1999.

Jeremy Bernstein, Albert Einstein and the Frontiers ofPhysics, Oxford University Press, 1996.

Alice Calaprice, editor, The Ultimate Quotable Einstein, Princeton University Press, 2010.

Ta-Pei Cheng, Einsteins Physics, Oxford University Press, 2013.

Ronald Clark, Einstein: The Life and Times, London: Hodder & Stoughton, 1973.

Albert Einstein, Ideas and Opinions, New York: Random House, 1954.

Albert Einstein, Relativity, New York: Crown 1961 (reprint in English of Einsteins only popular book; originally published by Holt, New York, 1921).

Albert Einstein, Autobiographical Notes, edited and translated by P. A. Schilpp, La Salle, Illinois: Open Court, 1979.

* Albert Einstein, The Collected Papers, Princeton University Press, 1987-2006 (see especially Volumes 1, 2 and 6, 1987, 1990 and 1997).

Lewis Carroll Epstein, Relativity Visualized, San Francisco: Insight Press, revised edition 1987.

Albrecht Flsing, Albert Einstein, translated by Ewald Osers, New York: Viking, 1997.

George Gamow, Mr Mr Tompkins in Paperback, Cambridge University Press, 1965.

John Gribbin, In Search of Schrdingers Cat, New York: Bantam, 1984.

John Gribbin, In Search of the Edge of Time, London: Bantam, 1992.

Mary Gribbin and John Gribbin, Time Travel for Beginners, London: Hodder, 2008.

Tony Hey and Patrick Walters, Einsteins Mirror, Cambridge University Press, 1997.

Walter Isaacson, Einstein, New York: Simon & Schuster, 2007.

Thomas Levenson, Einstein in Berlin, New York: Bantam, 2003.

Robert Millikan, The Autobiography, London: Macdonald, 1951.

Alexander Moskowski, Conversations with Einstein, translated by Henry Brose, London: Sidgwick & Jackson, 1970 (reprint of 1921 edition).

Dennis Overbye, Einstein in Love, New York: Viking, 2000.

*Abraham Pais, Subtle is the Lord, Oxford University Press, 1982.

Jrgen Renn and Robert Schulmann, ed., Albert Einstein, Mileva Maric: The Love Letters, translated by Shawn Smith, Princeton University Press, 1992.

John Rigden, Einstein 1905, Cambridge University Press, 2005.

Carl Seelig, Albert Einstein, translated by Mervyn Savill, London: Staples Press, 1956.

John Stachel, ed., Einsteins Miraculous Year, Princeton University Press, 1998.

Russell Stannard, The Time and Space of Uncle Albert, London: Faber, 1989.

Michael White and John Gribbin, Einstein: A Life in Science, London: Simon & Schuster, revised edition 2005.

Clifford Will, Was Einstein Right?, New York: Basic Books, 1986.

Other biographies by John and Mary Gribbin

Richard Feynman: A Life in Science, London: Penguin, 1998.

FitzRoy: The Remarkable Story of Darwins Captain and the Invention of the Weather Forecast, New Haven: Yale University Press, 2004.

He Knew He Was Right: The Irrepressible Life of James Lovelock, London: Penguin, 2009.

Introduction
to the American Edition

In 1905, Albert Einstein published four scientific papers that had a profound influence on the science of the 20th century. Everybody knows Einstein's name, and an equation from one of those papers, E = mc2, is the most famous equation in all of science. For another of his contributions that year, he received the Nobel Prize. All of this has resulted in 1905 being referred to as Einsteins annus mirabilis or miraculous year. If he had never done another stroke of scientific work after 1905, Einstein would still be remembered as a genius. But, amazing as these achievements were, none of this represented Einsteins greatest work. Exactly ten years later, in 1915, he presented his master-work to the Prussian Academy of Sciencesa theory of gravity, matter, space and time which we know as the General Theory of Relativity, and which he described as the most valuable theory of my life. It describes the evolution of the Universe, black holes, the behavior of orbiting neutron stars, gravitational lensing, and why clocks run slower on the surface of the Earth than in space. It even suggests the possibility of time travel. He completed this work in Berlin during the First World War, where he later suffered from malnutrition caused by food shortages resulting from the Allied blockade of Germany and was nursed by his cousin, Elsa, who became his second wife. The accuracy of his theory was confirmed by British astronomers, at a time when Britain and Germany were technically still at war. But even today the General Theory is less feted than the achievements of 1905, because it is regarded as too difficult, for ordinary mortals to comprehend. I hope to disabuse you of the year 1915 should be at least as celebrated as those of 1905.

The Special Theory of Relativity, one of the achievements of 1905, is special in the sense that it is restricted and only describes the behavior of things moving in straight lines at constant speed. The names alone tell you that the General Theory is a bigger deal, but because of the widespread (mis)conception that the General Theory is too difficult for ordinary mortals to understand, the events of 1915 have been less feted than the events of 1905. It is, in fact, easy to understand the basics of the General Theory, even if the equations have been taken on trust, and this understanding should convince youcorrecting the misconception that the Special Theory was Einsteins greatest achievementthat Einsteins greatest year was indeed 1915, not 1905. But I intend to demonstrate this by putting Einsteins science in the context of his life and work both before and after 1915, including his breakthrough year of 1905.

* * *

In February 2016, just as this edition of the book was going to press, a large team of scientists announced the first direct detection of the gravitational radiation predicted by Einstein in 1916, and described here in Chapter 4. This is seen by many as the ultimate proof of the accuracy of the General Theory of Relativity, although we already had firm evidence for the existence of such radiation from the behavior of objects known as binary pulsars. The experiment involves two laser beams, 4 km long, at right angles to each other, which are kept in step so that when their waves meet they cancel each other out and leave nothing. A pulse of gravitational radiation passing through the experiment gave a squeeze and stretch to the beams, so that they were briefly out of step, by a distance much less than the diameter of an atom, so that they interfered with one another and produced a measurable flicker. And an identical experiment many kilometers away saw an identical flicker just seven-thousandth of a second later, proving that the source was extraterrestrial, not caused by some lorry passing by on the highway, and travelled at the speed of light.