Richard A. Muller - Now - The Physics of Time

NOW

THE PHYSICS OF TIME

Richard A. Muller

Copyright 2016 by Richard A. Muller

All rights reserved

First Edition

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The Library of Congress has cataloged the printed edition as follows:

Names: Muller, R. (Richard), author.

Title: Now : the physics of time / Richard A. Muller.

Description: First edition. | New York ; London : W.W. Norton & Company,

[2016] | ?2016 | Includes index.

Identifiers: LCCN 2016012496| ISBN 9780393285239 (hardcover) |
ISBN 0393285235 (hardcover)

Subjects: LCSH: Space and time. | Entropy. | PhysicsPhilosophy.

Classification: LCC QC173.59.S65 M85 2016 | DDC 530.11dc23 LC record

available at http://lccn.loc.gov/2016012496

ISBN 978-0-393-28524-6 (e-book)

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CONTENTS

Now that enigmatic and ephemeral moment that changes its meaning every instanthas confounded priests, philosophers, and physicists, and with good reason. Understanding now requires knowledge of relativity, entropy, quantum physics, antimatter, backward time travel, entanglement, the Big Bang, and dark energy. Only now do we have all the physics in hand to understand now .

The elusive meaning of now has been a stumbling block in the development of physics. We understand time dilation from velocity and gravity, even the flipping of time in relativity theory, yet weve made no progress in explaining the most striking aspects of time: its flow and the meaning of now . The basic drawing board of physics known as a space-time diagram ignores these issues, and physicists sometimes perversely treat this absence as a strength and conclude that the flow of time is an illusion. Thats backward. As long as the meaning of now eludes us, further advances in understanding timethat key aspect of realitywill continue to be stalled.

My goal in this book is to bring together the essential physics, assembling pieces like a jigsaw puzzle until a clear picture of now emerges. For this process to work, we also have to find and remove jigsaw pieces that have been mistakenly jammed into the wrong places.

The broad range of relevant physics explains why the puzzle has remained elusive. Physics is not simple and linear, and by necessity this book covers an enormity of material, perhaps too much for a single volume. Feel free to skip around, using the index to go back to key ideas you may have missed. This story can also be thought of as a mystery, with a gradual accumulation of clues leading to a remarkable resolution.

My background is primarily experimental physics, the building and using of new hardware to measure and occasionally discover physical truths that were previously hidden. Two of my projects were directly related to our understanding of time: a measurement of the microwave debris from the Big Bang, and a precise determination of the past expansion of the universe, including the discovery of the dark energy that is accelerating that expansion. Although I admit to having written some purely theoretical papers, I did so mostly when funds to perform experiments were low, or when I thought theory was far off track. As far as I know, this is the only current book written specifically about time by a physicist deeply involved in experimental work, and I will try to give some insights on the challenges and frustrations that such work entails.

The path toward the understanding of now requires five parts.

In Part I, Amazing Time , I begin by discussing some solidly established yet still surprising aspects of time, uncovered principally by Albert Einstein. Not only does time stretch, flex, and flip, but such behavior affects our daily lives. GPS, the satellite system that keeps us from getting lost, depends exquisitely on Einsteins relativity equations, on these strange properties of time. It is relativity that brought us to think of four-dimensional space-time. The most important message of Part I is that we do understand much about time, and that the behavior of time is not simple but is well established. The pace of time depends on local conditions of velocity and gravity, and even the order of eventswhich event came firstis not a universal truth. Moreover, Einsteins theory of relativity gives us much of the structure that we need to understand the meaning of now .

In Part II, Broken Arrow , I remove one jigsaw piece that has been crammed in the wrong spot, the theory that has most inhibited progress in understanding now . This improperly placed piece of the puzzle is the theory of physicist Arthur Eddington, purporting to give an explanation for the arrow of time, the fact that the past determines the future and not the other way around. I do this by first presenting the best possible case in support of his theory, and only afterward showing its fatal flaws.

Eddington attributed the flow of time to the increase in entropy , a measure of disorder in the universe. We now know enormously more about the entropy of the universe than did Eddington in 1928 when he proposed the theory, and Ill argue that Eddington got it backward. The flow of time causes entropy to increase, not the other way around. Entropy production does not exert the tyranny that is often attributed to it. Control over the pathways of entropy turns out to be essential for our understanding of now .

Part III, Spooky Physics , brings in another important element for the understanding of now : the mysterious science of quantum physics. Quantum physics is perhaps the most successful theory of all timewith agreement between predictions and observations reaching ten decimal placesyet this theory is both disconcerting and distressing. The wraithlike behavior of quantum waves and their measurement blatantly violate Einsteins principles of relativity, but not in any way that can be directly observed or exploited. This behavior of the quantum wave challenges and develops our sense of reality, a sense that will prove essential for the elucidation of now . A most disturbingor perhaps liberatingconsequence of quantum physics is that the past no longer determines the future, at least not completely. Some of the most non-intuitive aspects of quantum physics, particularly a strange feature called entanglement , have been experimentally verified, and that (surprising!) experimental result suggests that limited ability to predict the future will remain a fundamental weakness of physics forever.

In Part IV, Physics and Reality , I explore the limitations of physics. Dont worrytime and now do not fall in this realm; they originate in physics, but our perception of them depends on our sense of reality, a sense that stretches beyond physics. Math represents a world of reality that cannot be verified by physics experiment, even something as simple as the irrationality of the square root of 2. But there are other issues that are real but not in the realm of physics, questions such as, what does the color blue look like ? The denial of nonphysics, nonmath truths has been named physicalism by philosophers. Physicalism is faith based and has all the trappings of a religion itself. Alas, against Einsteins fervent hopes, the evidence leads to the conclusion that physics is incomplete, that it never will be capable of describing all of reality.