Einstein's Relativity and the Quantum Revolution- Modern Physics for Non-Scientists.pdf

Einstein’s Relativity and

the

Quantum Revolution:

Modern Physics for

Non-Scientists

Part I

Professor Richard Wolfson

T HE T EACHING C OMPANY ®

Richard Wolfson, Ph.D.

Professor of Physics, Middlebury College

Richard Wolfson is Professor of Physics at Middlebury College, where he has

also held the George Adams Ellis Chair in the Liberal Arts. He did

undergraduate work at MIT and Swarthmore College, graduating from

Swarthmore with a double major in physics and philosophy. He holds a master’s

degree in environmental studies from the University of Michigan and a Ph.D. in

physics from Dartmouth College. His published research includes such diverse

fields as medical physics, plasma physics, solar energy engineering, electronic

circuit design, observational astronomy, and theoretical astrophysics. Professor

Wolfson’s current research involves the sometimes violently eruptive behavior

of the Sun’s outer atmosphere, or corona. He also continues an interest in

environmental science, especially global climate change. As a college professor,

Wolfson is particularly interested in making physics relevant to students from

all walks of academic life. His textbook, Physics for Scientists and Engineers

(Addison Wesley, 1999), is now in its third edition and has been translated into

several foreign languages. Wolfson is also an interpreter of science for

nonscientists; he has published in Scientific American and wrote Nuclear

Choices: A Citizen’s Guide to Nuclear Technology (MIT Press, 1993). The

original version of this course on physics was produced in 1995, and in 1996,

Wolfson produced another Teaching Company course, Energy and Climate:

Science for Citizens in the Age of Global Warming . Although he has been at

Middlebury for his entire post-Ph.D. career, Professor Wolfson has spent

sabbaticals at the National Center for Atmospheric Research in Boulder,

Colorado; at St. Andrews University in Scotland; and at Stanford University.

Table of Contents

Einstein’s Relativity and the Quantum Revolution:

Modern Physics for Non-Scientists

Part I

Professor Biography ........................................................................................... i

Foreword ............................................................................................................ 1

Lecture One Time Travel, Tunneling, Tennis, and Tea................. 3

Lecture Two Heaven and Earth, Place and Motion........................ 5

Lecture Three The Clockwork Universe .......................................... 7

Lecture Four Let There Be Light! ................................................ 11

Lecture Five Speed c Relative to What? ...................................... 14

Lecture Six Earth and the Ether: A Crisis in Physics ................. 18

Lecture Seven Einstein to the Rescue ............................................. 24

Lecture Eight Uncommon Sense: Stretching Time........................ 28

Lecture Nine Muons and Time-Traveling Twins ......................... 33

Lecture Ten Escaping Contradiction: Simultaneity Is

Relative ................................................................... 40

Lecture Eleven Faster than Light? Past, Future, and Elsewhere ...... 47

Lecture Twelve What about E=mc 2 , and Is Everything

Relative? ................................................................. 52

Timeline ............................................................................................................ 59

Glossary ............................................................................................................ 61

Bibliography ..................................................................................................... 66

Einstein’s Relativity and the Quantum Revolution:

Modern Physics for Non-Scientists

Scope:

The twentieth century brought two revolutionary changes in humankind’s

understanding of the physical universe in which we live. These revolutions—

relativity and the quantum theory—touch the very basis of physical reality,

altering our commonsense notions of space and time, cause and effect. The

revolutionary nature of these ideas endows them with implications well beyond

physics; indeed, philosophical debate continues to this day, especially over the

meaning of quantum physics.

Is time travel to the future possible? You bet—but if you don’t like what you

find, you can’t come back! Are there really such bizarre objects as black holes

that warp space and time so much that not even light can escape? Almost

certainly! And do the even weirder cousins of black holes, wormholes, exist—

perhaps affording us shortcuts to remote reaches of space and time? Quite

possibly! Is the universe governed by laws that strictly predict exactly what will

happen in the future or is it governed by chance? In part, by chance! All these

and other equally strange consequences flow from relativity and quantum

physics.

Many people think that relativity and quantum physics must be far beyond their

comprehension. Indeed, how many times have you heard it said of something

difficult that “it would take an Einstein to understand that”? To grasp these new

descriptions of physical reality in all their mathematical detail is indeed

daunting. But the basic ideas behind relativity and quantum physics are, in fact,

simple and comprehensible by anyone; for example, a single, concise English

sentence suffices to state Einstein’s theory of relativity.

This course presents the fundamental ideas of relativity and quantum physics in

twenty-four lectures intended for interested people who need have no

background whatsoever in science or mathematics. Following a brief history of

humankind’s thinking about physical reality, the lectures outline rigorously the

logic that led inexorably to Einstein’s special theory of relativity. After an

exploration of the implications of special relativity, we move on to Einstein’s

general theory of relativity and its interpretation of gravity in terms of the

curving of space and time. We see how the Hubble Space Telescope provides

some of the most striking confirmations of general relativity, including near-

certain confirmation of the existence of black holes. Then we explore

quandaries that arose as physicists began probing the heart of matter at the

atomic and subatomic scales, quandaries that led even the great physicist

Werner Heisenberg to wonder “can nature possibly be as absurd as it seems to

us in these atomic experiments?” The resolution of those quandaries is the

quantum theory, a vision of physical reality so at odds with our experience that

even our language fails to describe the quantum world. After a brief exposition

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