9780241992036

So he wrote it himself.

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In This Way to the Universe, Dine takes us on a fascinating tour through the history of modern physics – from Newtonian to quantum mechanics, from particle to nuclear physics – delving into the wonders of our universe at its largest, smallest, and within our daily lives. If you are looking for the one book to help you understand physics, written in language anyone can follow, this is it.

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UN I V MIC HA DIN EL E

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I S B N 978-0-241-99203-6

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APPROVED COVER ON B3

’ sk a n t a e w d u o y o g id t thin but were afra s ery c i s y h p t u o v b wa ‘E kno amvada Natarajan, author of avens to He Priy Mapping the

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When leading theoretical physicist Professor Michael Dine was asked where you could find an accessible and authoritative book that would teach you about the Big Bang, dark matter, the Higgs boson and the cutting edge of physics now, he had nothing he could recommend.

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‘Extra o Leonar rdin d S ary us sk ’ ind

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of e l c ‘A tour de for nta M e all of fundam ght i B B C S ky a t N

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This Way to the Universe ‘This book is a rare event: a grand overview of the leading ideas in modern fundamental physics, presented by someone who is a true master’ Sean Carroll, theoretical physicist at the California Institute of Technology, host of the Mindscape podcast and author of From Eternity to Here, The Particle at the End of the Universe and The Big Picture ‘This book, written by one of the great masters of modern physics, is an extraordinary journey into what we know, what we hope to know and what we don’t know about the universe and the laws that govern it. Unlike other books on the subject it does not try to sell you the author’s pet theory. In a clear and honest way it lays out all the most important problems, puzzles and potential solutions that modern physics faces’ Leonard Susskind, professor of theoretical physics at Stanford University, author of The Cosmic Landscape, The Black Hole War and The Theoretical Minimum series ‘Michael Dine takes the reader on a fascinating and wideranging tour of the world of physics, both theoretical and experimental, emphasizing the remarkable discoveries that make up modern physics and the daunting challenges that remain. Dine is a leader in theoretical physics and tells the story of the last few decades based on his own personal experiences and involvement’ Edward Witten, theoretical physicist and professor at the Institute for Advanced Study ‘Everything you wanted to know about physics but were afraid to ask. This Way to the Universe is a fascinating and sweeping tour of the history of ideas in modern physics and cosmology from a remarkable theoretical physicist and engaging storyteller. A riveting read, the book offers a ringside view to many of the latest theoretical and experimental developments from a key protagonist. A treat for the intellectually curious’ Priyamvada Natarajan, professor of astronomy at Yale University and author of Mapping the Heavens

‘Dine’s enthusiastic storytelling makes the read worth it for those who want to finally wrap their mind around string theory or the Higgs boson’ Tess Joosse, Scientific American ‘It is not an easy task to take the complexities of theoretical physics . . . and translate it into common prose. It is even more difficult to make it accessible to the lay enthusiast. The author has done an admirable job and hasn’t shirked away from many of the more difficult and arcane topics. As a comprehensive and uncompromising tour de force of literally all of fundamental physics, there can be few better alternatives’ BBC Sky at Night Magazine ‘Excellent popular science’ Kirkus Reviews

ab o ut the author Michael Dine is Distinguished Professor of Physics at the Santa Cruz Institute for Particle Physics, University of California.

One of the world’s leading physicists, he has made important contributions to our understanding of particle physics and string theory, has proposed arguably the leading candidate for the identity of the dark matter, and put forth some of the most promising ideas to explain why our universe consists of something rather than nothing. This is his first book for a general readership.

TH TH I SI SWW AYAY T OT O T HTEH E

UU NN I VI E VR ER SE SE

T THHI SI SWWAY AY T OT OT HTEH E

UUNNI VI VEERRSSEE a journey a journey intointo physics physics

M IM CIH CAHEALE LD ID NIEN E

P EN GU I N B O O K S

PENGUIN BOOKS UK | USA | Canada | Ireland | Australia India | New Zealand | South Africa Penguin Books is part of the Penguin Random House group of companies whose addresses can be found at global.penguinrandomhouse.com.

First published in the United States of America by Dutton 2022 First published in Great Britain by Viking 2022 Published in Penguin Books 2023 001 Copyright © Michael Dine, 2022 The moral right of the author has been asserted While the author has made every effort to provide accurate telephone numbers, internet addresses, and other contact information at the time of publication, neither the publisher nor the author assumes any responsibility for errors or for changes that occur after publication. Further, the publisher does not have any control over and does not assume any responsibility for author or third-party websites or their content.

Printed and bound in Great Britain by Clays Ltd, Elcograf S.p.A. The authorized representative in the EEA is Penguin Random House Ireland, Morrison Chambers, 32 Nassau Street, Dublin D02 YH68 A CIP catalogue record for this book is available from the British Library ISBN: 978–0–241–99203–6

www.greenpenguin.co.uk Penguin Random House is committed to a sustainable future for our business, our readers and our planet. This book is made from Forest Stewardship Council® certified paper.

This book is dedicated to Melanie, Aviva, Jeremy, Shifrah, Matt, and Oren

C OCNO TE NN TE TS NTS

STEP STEP ONEONE 1. Surveying 1. Surveying the Universe the Universe

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2. Can 2. Can We Take We Take Space Space and and TimeTime for Granted? for Granted?

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4. Can 4. Can Quantum Quantum Mechanics Mechanics Predict Predict the Future? the Future?

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5. Fruits 5. Fruits of the ofNuclear the Nuclear Age Age

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3. What 3. What Do We DoMean We Mean

by Universe?

by Universe?

STEP STEP T WO T WO

6. The 6. Weight The Weight of the ofSmallest the Smallest Things Things

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7. Stardom 7. Stardom

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THETHE NEXNEX T STEPS T STEPS 8. Why 8. Why Is There Is There Something Something Rather Rather ThanThan Nothing?

Nothing?

155 155

9. “The 9. “The Large Large Number Number Problem” Problem”

175 175

10. What 10. What Is theIsUniverse the Universe Made Made Of? Of?

193 193

11. The 11. Dark The Dark Energy Energy

219 219

ix

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ANDAND STEPPING STEPPING INTO INTO THETHE UNSTABLE UNSTABLE 12. At 12.the AtBeginning the Beginning of Everything of Everything

233 233

13. Can 13. Can We Get We to Get a Final to a Final Theory Theory Without Without Getting Getting Up Up fromfrom Our Chairs?

Our Chairs?

249 249

14. The 14. Landscape The Landscape of Reality of Reality

293 293

15. Rolling 15. Rolling the Dice the Dice of Theoretical of Theoretical Physics Physics

317 317

NotesNotes

323 323

Acknowledgments Acknowledgments

327 327

IndexIndex

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t seems t seems to betoan beextraordinary an extraordinary moment. moment.

On the On one the one hand, hand, we we faceface daunting daunting challenges: challenges: climate climate change, change, global global pandemics, pandemics, the threat the threat of nuclear of nuclear war.war.

On the On other the other hand, hand, as a as species, a species, we we havehave knowledge knowledge of the of world— the world— and and the universe— the universe— around around us us beyond beyond anything anything humans humans might might havehave imagined imagined eveneven a century a century ago.ago.

No matter No matter whatwhat happens, happens, we have we have an unprecedented an unprecedented un- understanding derstanding of the of the natural natural world world of which of which our our dailydaily experiexperiences ences sample sample onlyonly a tiny a tiny corner. corner.

OurOur liveslives playplay out on outscales on scales of of centimeters, centimeters, meters, meters, kilometers, kilometers, perhaps perhaps thousands thousands of kilomeof kilometers.ters.

But But we know we know about about nature nature on smaller on smaller scales— scales— far, far, far far smaller smaller thanthan the size the size of anofatomic an atomic nucleus. nucleus.

We also We also know know about about the universe the universe out to outunimaginably to unimaginably largelarge distances. distances.

EvenEven moremore amazing amazing is what is what we know— we know— really really know— know— about about events events bil- billionslions of years of years ago,ago, and and we can we can make make statements statements withwith nearnear cer- certainty tainty about about whatwhat will will happen happen to the to universe the universe for the for next the next few few tenstens of billions of billions of years. of years.

An extraordinary An extraordinary moment moment indeed. indeed.

MostMost of usofhave us have heard heard about about faraway faraway starsstars and and galaxies, galaxies, 3

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havehave somesome inkling inkling thatthat the universe the universe emerged emerged fromfrom a biga bang big bang billions billions of years of years ago.ago.

But precisely But precisely howhow largelarge and and howhow old isold the is the universe? universe?

Where Where did it didcome it come from? from?

What What is itsisultimate its ultimate fate?fate?

HowHow do we dofiwe ndfianswers nd answers to these to these questions? questions?

We We are are aware aware of atoms of atoms and and maybe maybe somewhat somewhat aware aware of of things things smaller smaller thanthan atoms. atoms.

HowHow can can we possibly we possibly know know about about atomic atomic nuclei nuclei thatthat are far aretoo far small too small to see to with see with the most the most powerpowerful microscopes? ful microscopes?

HowHow do these do these tinytiny things things control control the operathe operationtion of the of universe the universe at large, at large, as well as well as events as events like like making making a a sandwich, sandwich, using using a credit a credit card,card, or driving or driving to work? to work?

From From the the largest largest scales scales to the to smallest the smallest scales, scales, our our universe universe can can seemseem im- impossibly possibly mysterious. mysterious.

CanCan we do wemore do more thanthan speculate speculate about about the the architecture architecture of the of cosmos the cosmos and and its building its building materials? materials?

CanCan we we construct construct experiments experiments thatthat will will answer answer our our questions questions about about reality reality at such at such fantastic fantastic scales? scales?

As IAs write I write this,this, the world the world is (hopefully) is (hopefully) at the at tail the tail end end of of the the Covid-19 Covid-19 pandemic. pandemic.

From From thisthis ordeal, ordeal, we’re we’re all now all now fa- familiar miliar withwith the the signifi signifi cance cance of powers of powers of 10. of In 10. the In the earlyearly stages stages of the of the outbreak, outbreak, the the number number of cases of cases in some in some councountriestries waswas growing growing by nearly by nearly a factor a factor of 10ofevery 10 every few few weeks. weeks.

Many Many countries countries saw saw spikes spikes in the in fall the fall of 2020 of 2020 or early or early in the in the winter winter of 2021 of 2021 withwith similar similar growth growth rates. rates.

With, With, say, say, a growth a growth of aoffactor a factor of 10ofin10ainmonth, a month, 1,000 1,000 cases cases a day a day would would turnturn intointo 10,000 10,000 cases cases in one in one month, month, 100,000 100,000 in two in two months, months, and and a million a million cases cases a day a day in three in three months. months.

Nations Nations reacted reacted withwith varying varying degrees degrees of speed of speed and and severity, severity, but but nonenone allowed allowed suchsuch extreme extreme growth growth to continue. to continue.

At the At the end end of 2020, of 2020, withwith the the appearance appearance of eff ofective effective vaccines, vaccines, the the trend trend reversed, reversed, withwith drastic drastic decreases decreases in the in the number number of daily of daily newnew cases, cases, 4

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approaching approaching zerozero in some in some countries. countries.

Hopefully Hopefully this this willwill con-continue tinue worldwide. worldwide.

But But powers powers of 10ofneed 10 need not not always always tell tell suchsuch a grim a grim story. story.

TheyThey are aare valuable a valuable tool tool for thinking for thinking about about nature. nature.

We We hu- humans mans occupy occupy a tiny a tiny planet planet in ain vast a vast universe. universe.

At the At the same same time, time, there there is a world is a world of far of tinier far tinier things— things— molecules, molecules, atoms, atoms, protons, protons, neutrons, neutrons, and and electrons. electrons.

Powers Powers of 10ofare 10 also are also a usea useful concept ful concept in these in these happier happier pursuits. pursuits.

In 1977, In 1977, while while a gradua graduate student ate student visiting visiting the the Smithsonian Smithsonian Institution Institution withwith my my brother, brother, I watched I watched the the video video Powers Powers of Ten, of Ten,

by Charles

by Charles and and RayRay Eames Eames (a couple (a couple bestbest known known for their for their workwork in industrial in industrial design). design).

ThisThis beautiful beautiful fi lmfisummarized lm summarized our our understanding understanding of nature of nature at that at that time, time, on the on the largest largest and and smallest smallest scales. scales.

Starting Starting withwith a couple a couple enjoying enjoying a beautiful a beautiful spring spring day,day, oc- occupying cupying a space a space maybe maybe two two meters meters across across in each in each direction, direction, it explored it explored scales scales progressively progressively larger larger by factors by factors of 10— of 10— parks, parks, cities, cities, states, states, nations, nations, the the planet, planet, the the solarsolar system, system, galaxies, galaxies, andand clusters clusters of galaxies. of galaxies.

It then It then proceeded proceeded in the in the other other direction, direction, describing describing smaller smaller scales— scales— parts parts of the of the human human anatomy, anatomy, thenthen cells,cells, atoms, atoms, and and the nuclei the nuclei of atoms. of atoms.

It sumIt summarized marized for me for pretty me pretty wellwell whatwhat I was I was learning learning in my in studmy studies. To ies.be Tohonest, be honest, there there waswas a good a good dealdeal I didn’t I didn’t yet know yet know in in thatthat fi lm.fi lm.

A lotAhas lot has happened happened in the in subsequent the subsequent decades. decades.

We underWe understand stand nature nature at scales at scales several several powers powers of 10oflarger 10 larger and and several several powers powers of 10ofsmaller, 10 smaller, and and we have we have cluesclues to many to many more more pow-powers of ers10ofin10each in each direction. direction.

I have I have beenbeen a witness a witness to, and to, and in in some some cases cases a participant a participant in, many in, many of these of these developments. developments.

Telling Telling the story the story of nature of nature on this on this vastvast range range of scales of scales is the is the 5

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subject subject of this of this book. book.

The The storystory follows follows this this progress progress in physin physics, ics, astrophysics, astrophysics, and and cosmology. cosmology.

I will I will onlyonly occasionally occasionally mention mention the the spectacular spectacular discoveries discoveries of the of the pastpast century century in in biology, biology, medicine, medicine, computer computer andand cognitive cognitive science, science, andand other other fields. fields.

These These advances advances havehave beenbeen the product the product of dedicated of dedicated workwork of experimenters of experimenters and and theorists. theorists.

The The dichotomy dichotomy between between the the two two can can be abe confusing a confusing one,one, but but one one which which will,will, I hope, I hope, be- become come clearclear in these in these pages. pages.

While While I seriously I seriously considered considered a a career career in experimental in experimental physics, physics, as a as student a student I fellI in felllove in love withwith theoretical theoretical physics. physics.

ThisThis was,was, professionally, professionally, a risky a risky choice, choice, and and some some of my of mentors my mentors discouraged discouraged me, me, telling telling me that me that the the competition competition waswas just just too too stiffstiff . While . While I believed I believed them, them, and and waswas by no bymeans no means convinced convinced I had I had the stuff the stuff for theory, for theory, I was I was in love in love withwith the subject. the subject.

My graduate My graduate student student daysdays werewere spent spent studying studying phenomena phenomena at the at the smallest smallest scales scales thenthen accessible, accessible, - 14 centiabout about one-onethirdthird the size the size of an ofatomic an atomic nucleus, nucleus, or 10or- 1410centimeters meters (a hundredth (a hundredth of a of trillionth a trillionth of a of centimeter). a centimeter).

I have I have to to confess confess thatthat I was I was hardly hardly a brilliant a brilliant student, student, but my but teachers my teachers had had faithfaith in me, in me, and and I went I went on to ondo to ado postdoctoral a postdoctoral fellowfellowshipship at the at Stanford the Stanford Linear Linear Accelerator Accelerator Center Center in Menlo in Menlo Park,Park, California.

California.

Here, Here, I was I was involved involved in interpreting in interpreting experiments experiments on still on still smaller smaller length length scales. scales.

Among Among my mentors my mentors werewere Sid- Sidney ney Drell, Drell, a leading a leading voicevoice for nuclear for nuclear armsarms control, control, and and LeonLeonard ard Susskind, Susskind, thenthen a brash a brash young young theorist, theorist, whowho had had recently recently come come to Stanford. to Stanford.

Still,Still, though, though, I had I had a hard a hard timetime finding finding my my wayway in that in that period. period.

The The problems problems I worked I worked on didn’t on didn’t really really move move me. me.

After After two two years years at Stanford, at Stanford, I moved I moved to a to similar a similar position position 6

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at the at the Institute Institute for Advanced for Advanced Study Study in Princeton. in Princeton.

The The InstiInstitutetute is anisinstitution an institution exclusively exclusively devoted devoted to theory, to theory, and and it is it is famed, famed, in part, in part, because because of the of faculty the faculty of itsofearly its early days.days.

ThisThis includes, includes, mostmost notably, notably, Albert Albert Einstein, Einstein, but but alsoalso figures figures like like J. Robert J. Robert Oppenheimer Oppenheimer (who(who headed headed the atomic the atomic bomb bomb effort effort at Los at Los Alamos Alamos during during the Second the Second World World War), War), JohnJohn von von Neu-Neumann mann (an early (an early computer computer pioneer), pioneer), and and George George Kennan Kennan (the (the diplomat diplomat whowho shaped shaped much much of US ofpolicy US policy relative relative to the to Soviet the Soviet Union Union in the in early the early daysdays of the of Cold the Cold War).

War).

Its current Its current faculty— faculty— including including Edward Edward Witten, Witten, Nathan Nathan Seiberg, Seiberg, JuanJuan Maldacena, Maldacena, and and Nima Nima ArkaniArkaniHamed— Hamed— are are among among the the premier premier living living theoretical theoretical physicists physicists in the in the world. world.

In this In this environment, environment, I I found found my scientifi my scientifi c bearings c bearings and and started started to probe to probe questions questions beyond beyond the the levellevel of our of our thenthen current current understanding. understanding.

From From there, there, I went I went on toonfito ve fiproductive ve productive years years on the on faculty the faculty of the of the CityCity College College of New of New York, York, before before moving, moving, for family for family reasons, reasons, backback to the to West the West Coast, Coast, joining joining the faculty the faculty at the at University the University of California of California at Santa at Santa Cruz.

Cruz.

I have I have spent spent the subsequent the subsequent three three decades decades there. there.

UC Santa UC Santa CruzCruz sits amidst sits amidst towering towering redwoods, redwoods, overlooking overlooking Monterey Monterey Bay.Bay. When When firstfiestablished rst established in 1965, in 1965, it was it was committed committed to a to radical, a radical, 1960s 1960s vision vision of education of education and and engagement. engagement.

Its unIts unofficial official motto motto was was “We“We are not are Berkeley,” not Berkeley,” meaning meaning thatthat its facits facultyulty and and administration administration werewere committed committed to their to their students, students, not not just just to research. to research.

ThatThat vision vision survives, survives, but for butserendipitous for serendipitous rea- reasons,sons, UCSC UCSC alsoalso became became a research a research powerhouse. powerhouse.

The The astronastronomyomy enterprise enterprise of the of UC the system, UC system, the Lick the Lick Observatory, Observatory, moved moved its headquarters its headquarters to the to Santa the Santa CruzCruz campus campus fromfrom Mount Mount HamHamilton. ilton.

Earth Earth scientists scientists werewere attracted attracted to the to the campus campus by its by its 7

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proximity proximity to major to major faultfault systems, systems, marine marine biologists biologists by the by rich the rich ecology ecology of the of nearby the nearby bay;bay; biologists, biologists, chemists, chemists, and and mathematmathematicians icians werewere excited excited by the by opportunity the opportunity to work to work in the in natural the natural beauty beauty of this of this landscape. landscape.

UCSC UCSC alsoalso became became a center a center for parfor particleticle physics, physics, because because of the of commissioning the commissioning of a of revolutionary a revolutionary newnew instrument instrument for particle for particle physics physics nearby nearby at the at Stanford the Stanford Lin- Linear Accelerator ear Accelerator Center.

Center.

I arrived I arrived much much later,later, in 1990, in 1990, imagining imagining a hippya hippydippy dippy in- institution stitution in the in woods. the woods.

AndAnd so itso was, it was, but but I discovered I discovered at the at the same same timetime a rich a rich intellectual intellectual and and scientifi scientifi c environment. c environment.

For For the same the same personal personal reasons reasons thatthat brought brought me to meSanta to Santa Cruz, Cruz, I I actually actually livedlived “over “over the the hill”hill” on the on the other other sideside of the of the Santa Santa CruzCruz Mountains, Mountains, in San in San Jose,Jose, partpart of the of Silicon the Silicon Valley.

Valley.

For-Fortunately, tunately, fromfrom the very the very start,start, I had I had a cara pool car pool withwith a group a group of of colleagues. colleagues.

At the At time, the time, this this group group included included fourfour high-highenergy energy physicists, physicists, working working on experiments on experiments at the at the Stanford Stanford Linear Linear Accelerator Accelerator Center, Center, the Fermi the Fermi National National Accelerator Accelerator Laboratory Laboratory (Fermilab, (Fermilab, located located nearnear Chicago), Chicago), and and CERN, CERN, the the big big EuroEuropeanpean laboratory laboratory in Geneva. in Geneva.

There There werewere alsoalso two two astronomers. astronomers.

TwoTwo of the of the experimenters experimenters werewere playing playing leading leading rolesroles in the in the Superconducting Superconducting Super Super Collider Collider (SSC), (SSC), planned planned as the as world’s the world’s largest largest particle particle accelerator, accelerator, thenthen in the in the initial initial stages stages of conof construction struction nearnear Dallas, Dallas, Texas.

Texas.

It was It was designed designed to accelerate to accelerate two two beams beams of protons of protons to enormous to enormous energies, energies, and and thenthen to smash to smash them them together, together, examining examining the products the products of the of collisions. the collisions.

In aIn a multibillionmultibilliondollar dollar project project involving involving thousands thousands of PhD of PhD scienscientists,tists, my car my pool car pool partners partners had had the principal the principal responsibility responsibility for for tracking tracking particles particles just just as they as they emerged emerged fromfrom the the collision. collision.

OneOne of the of the astronomers astronomers waswas working working on understanding on understanding 8

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planets. planets.

At that At that time,time, the existence the existence of planets of planets beyond beyond our our so- solar system lar system was was a matter a matter of speculation. of speculation.

All that All that changed changed start-starting ing in 1995 in 1995 withwith the the firstfidiscovery rst discovery of an of extrasolar an extrasolar planet. planet.

Astronomers Astronomers at Santa at Santa CruzCruz made made crucial crucial contributions contributions to the to the breakthrough breakthrough technology technology and and to the to the underlying underlying planetary planetary theory. theory.

The The other other astronomer astronomer waswas a cosmologist, a cosmologist, one one of the of the originators originators of the of theory the theory of how of how darkdark matter matter led to ledthe to formathe formationtion of the of stars the stars and and galaxies. galaxies.

In 1993, In 1993, President President Bill Bill Clinton Clinton recognized recognized thatthat as the as costs the costs of the of SSC the SSC rose,rose, it became it became more more and and more more vulnerable vulnerable to the to the surging surging politics politics of government of government spending. spending.

Congress Congress fi nally fi nally killed killed the the project project one one day day in the in the fall.fall.

I expected I expected my my col- colleagues leagues to spend to spend a few a few daysdays mourning, mourning, but but by the by the nextnext morning, morning, theythey werewere in the in the car car discussing discussing a call a call theythey had had received received fromfrom the big the laboratory big laboratory in Geneva, in Geneva, Switzerland, Switzerland, in- inviting viting them them to join to join a project a project there, there, known known as the as Large the Large Had-Hadron ron Collider Collider (LHC), (LHC), still still in early in early stages stages of development. of development.

TheyThey agreed, agreed, and and immediately immediately launched launched intointo workwork on the on developthe development ment of a of large a large detector detector for elementary for elementary particles, particles, known known as as ATLAS. ATLAS. It would It would be fibe fteen fifteen years years before before thisthis machine machine waswas ready ready to operate. to operate.

There There werewere many many successes successes and and setbacks setbacks on the on way, the way, involving involving science, science, technology, technology, and and funding. funding.

The The mostmost devastating devastating waswas a magnet a magnet failure, failure, in 2008, in 2008, which which greatly greatly damaged damaged the machine. the machine.

The The recovery recovery tooktook two two years, years, but but by 2010, by 2010, the the accelerator accelerator waswas up and up and working working well.well.

In In 2012, 2012, two two experimental experimental teams teams at the at the LHCLHC discovered discovered the the Higgs Higgs particle. particle.

As aAs theorist, a theorist, my work my work involves, involves, among among other other things, things, trying trying to understand to understand the results the results of experiments of experiments and and to anticipate to anticipate pos-pos9

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sibilities sibilities for future for future experiments. experiments.

My My closeclose connections connections withwith experimental experimental colleagues colleagues havehave helped helped keepkeep me honest, me honest, focused focused on questions on questions we can we can really really hopehope to answer to answer in experimentally in experimentally verifi verifi ableable ways— ways— or atorleast at least to distinguish to distinguish those those we can we can and and those those we can’t. we can’t.

Much Much of my of research my research effort effisort devoted is devoted to sorting to sorting out precisely out precisely thesethese issues. issues.

What What might might account account for the for mass the mass of of the Higgs the Higgs boson? boson?

What What might might the dark the dark matter matter consist consist of and of and under under whatwhat circumstances circumstances might might we hope we hope to fito ndfiit? ndIsit?string Is string theory theory subject subject to experimental to experimental test?test?

OurOur conversations conversations in the in the car were car were oftenoften about about our children, our children, restaurants, restaurants, sports, sports, and and pol- politicsitics (real(real and and academic), academic), but but theythey werewere mostly mostly about about science. science.

Just Just as my as car my pool car pool partners partners havehave triedtried to teach to teach me about me about the the challenges challenges of building of building electronics electronics thatthat can can withstand withstand intense intense bursts bursts of radiation, of radiation, theythey havehave suffered suffered through through my my explanexplanations ations of the of latest the latest theoretical theoretical ideasideas and and theirtheir promise promise and and limi-limitations. tations.

My students My students at UCSC at UCSC havehave alsoalso keptkept me focused me focused on what’s on what’s exciting exciting in science. in science.

I frequently I frequently teach teach a course a course withwith the title the title “Modern “Modern Physics.”

Physics.”

It starts It starts withwith Einstein Einstein and and relativity, relativity, moves moves to the to development the development of quantum of quantum mechanics, mechanics, and and thenthen proceeds proceeds through through the the spectacular spectacular developments developments of the of the twentieth twentieth and and earlyearly twentytwentyfirstficenturies. rst centuries.

ThisThis bookbook willwill cover cover an even an even broader broader sweep sweep of ideas, of ideas, and and my hope my hope is toisconvey to convey excitement excitement about about whatwhat we understand, we understand, and and appreciation appreciation of the of mysteries the mysteries we currently we currently confront. confront.

The The discovery discovery of the of the Higgs Higgs particle, particle, of dark of dark matter matter and and darkdark energy, energy, along along withwith precision precision studies studies of the of big the bang, big bang, il- illustrate lustrate an understanding an understanding of our of our place place in the in the universe universe

10

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beyond beyond anything anything thatthat humanity humanity has has everever known. known.

At the At the same same time,time, we have we have burning burning questions. questions.

For some For some of these, of these, we we havehave a clear a clear pathpath to answers, to answers, for others for others less less so. Iso. firmly I firmly be- believelieve thatthat this this science science is not is not so far so removed far removed fromfrom the ordinthe ordinary ary events events of our of our liveslives thatthat we can’t we can’t all share all share in both in both the the understanding understanding and and the the mostmost pressing pressing questions. questions.

I intend I intend to to illuminate illuminate whatwhat questions questions are likely are likely to betoresolved, be resolved, say, say, overover the next the next decade, decade, by experiments by experiments or new or new theories, theories, and and which which onesones maymay not not be accessible. be accessible.

ThisThis bookbook willwill explore explore many many orders orders of magnitude of magnitude beyond beyond those those which which the the creators creators of the of the Powers Powers of Ten of Ten video video could could contemplate. contemplate.

We will We will journey journey across across scales scales bothboth voluminous voluminous and and microminiature, microminiature, but but we’llwe’ll alsoalso travel travel the scales the scales of time. of time.

OurOur clock clock willwill start, start, t= 0, t= at0,the at the big bang. big bang.

On this On this clock, clock, our our present present instant instant is about is about 13 billion 13 billion years years later,later, or 13 or x1310x9 109 years. years.

From From our our present present moment, moment, we’llwe’ll looklook backback to times to times when when starsstars and and galaxies galaxies began began to form— to form— 1 billion 1 billion years years afterafter the big the bang, big bang, and and further further to the to earliest the earliest times times we completely we completely understand— understand— three three minutes minutes afterafter the big the bang, big bang, when when hydrohydrogen gen and and helium helium werewere produced produced in ainhot, a hot, cosmic cosmic soup. soup.

But But we’llwe’ll looklook backback much much earlier— earlier— to times to times for which for which we have we have onlyonly scattered scattered bits bits of evidence, of evidence, when when the the universe universe waswas per-perhapshaps a billionth a billionth of a of second a second old, old, when when matter matter itselfitself maymay havehave beenbeen created. created.

Ultimately, Ultimately, we’llwe’ll peekpeek behind behind the the curtain curtain of of the the big big bang, bang, asking asking whatwhat maymay havehave come come before, before, and and en- encounter counter controversial controversial ideas ideas like like the the multiverse. multiverse.

ThisThis ideaidea provides provides a compelling a compelling explanation explanation of one— of one— andand maybe maybe more more thanthan one— one— of nature’s of nature’s greatest greatest mysteries. mysteries.

It isIteven is even

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conceivable conceivable thatthat we could we could fi ndfiobservational nd observational evidence evidence for for thisthis bizarre bizarre possibility. possibility.

Experiment Experiment andand Theory Theory Perhaps Perhaps more more thanthan mostmost sciences, sciences, physics physics is riven. is riven.

ThisThis maymay sound sound bad,bad, but it but has it has enabled enabled principled, principled, disciplined disciplined investiinvestigations gations of much of much thatthat initially initially seemed seemed utterly utterly bizarre. bizarre.

PhysiPhysicistscists divide divide intointo two two groups: groups: those those whowho devote devote the the bulkbulk of of theirtheir timetime to designing, to designing, building, building, running, running, and and analyzing analyzing the data the data fromfrom experiments experiments and and those those whowho spend spend the bulk the bulk of of theirtheir timetime inventing inventing theories, theories, predicting predicting the the results results of proof proposed posed experiments, experiments, and and comparing comparing experimental experimental results results withwith theories. theories.

Some Some of these of these theories theories are are designed designed to acto account count for existing for existing experimental experimental results, results, some some to account to account for for a mysterious, a mysterious, poorly poorly understood understood feature feature of nature of nature and and its its laws.laws.

ThisThis waswas not not always always true.true.

Newton, Newton, whowho did did much much to to shape shape the the modern modern fieldfiof eldphysics, of physics, waswas bothboth an experimenan experimentalisttalist and and theorist. theorist.

He performed He performed important important measurements, measurements, studying, studying, for example, for example, the properties the properties of light of light (coming (coming to noto notoriously toriously wrong wrong conclusions). conclusions).

He invented He invented the the calculus, calculus, one one of the of the mostmost important important toolstools of the of the modern modern theorist theorist or exor experimentalist, perimentalist, and and wrote wrote down down the the basicbasic lawslaws of motion, of motion, as as wellwell as aas theory a theory of gravitation of gravitation thatthat survived, survived, virtually virtually un- unscathed, scathed, for almost for almost two two hundred hundred years. years.

But But by the by late the late ninenineteenth teenth century, century, theory theory had had emerged emerged as aasspecialization, a specialization, practiced practiced in those in those daysdays by abyrather a rather small small group. group.

ThisThis re- reflected, flected, at least at least in part, in part, the the growing growing technological technological 12

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sophistication sophistication of experiments of experiments and and a similar a similar growth growth in the in the mathematical mathematical demands demands of theoretical of theoretical analysis. analysis.

EvenEven then, then, the Scotch the Scotch physicist physicist James James Clerk Clerk Maxwell, Maxwell, whowho put put the laws the laws of electricity of electricity and and magnetism magnetism into into theirtheir finalfiform nal form in the in 1860s, the 1860s, alsoalso did experiments did experiments withwith colorcolor and and established established the Cavendish the Cavendish Lab Lab at Cambridge at Cambridge University University in the in latter the latter partpart of his ofcareer. his career.

An An earlyearly notable notable purepure theorist theorist waswas the Dutch the Dutch physicist physicist Hendrik Hendrik Lorentz, Lorentz, who,who, among among many many other other accomplishments, accomplishments, wrote wrote down down a precursor a precursor to Einstein’s to Einstein’s relativity relativity theory theory and and developed developed an early an early theory theory of the of electron. the electron.

The The paradigm paradigm of the of modern the modern theorist, theorist, of course, of course, is Albert is Albert Einstein.

Einstein.

Einstein Einstein burst burst ontoonto the the scene scene in 1905, in 1905, withwith three three remarkable remarkable pieces pieces of work. of work.

The The two two mostmost famous famous of these of these are are his theory his theory of special of special relativity relativity and and the the photoelectric photoelectric effect, effect, for which for which he won he won the the Nobel Nobel Prize.

Prize.

The The average average physics physics stu- studentdent is less is less aware aware of his of work his work on the on Brownian the Brownian motion. motion.

But But this this workwork did did much much to establish to establish the reality the reality of atoms, of atoms, gavegave a a reasonably reasonably goodgood estimate estimate of the of number the number of atoms of atoms in a in cubic a cubic centimeter centimeter of water of water (Avogadro’s (Avogadro’s number), number), and and had had a profound a profound influence influence not not onlyonly in physics in physics but but in chemistry in chemistry and and biology. biology.

All All of these of these werewere products products of some of some combination combination of pure of pure thought thought and and analysis analysis of data of data fromfrom existing existing experiments. experiments.

It is It is a mold a mold thatthat all who all who call call themselves themselves theoretical theoretical physicists physicists try try to emulate. to emulate.

But But Einstein Einstein spoke spoke wistfully wistfully of his of own his own aspiraspirationation of doing of doing bothboth experimental experimental and and theoretical theoretical physics. physics.

Of Of Newton, Newton, he wrote: he wrote: “Nature, “Nature, to him, to him, waswas an open an open bookbook . . . In . . . In one one person person he combined he combined the the experimenter, experimenter, the the theorist, theorist, the the mechanic, mechanic, and,and, not not least, least, the the artist artist in exposition in exposition . . . .He . . He stands stands before before us certain, us certain, and and alone: alone: his joy his in joycreation in creation and and 13

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his his minute minute precision precision are are evident evident in every in every word word and and every every figure.” figure.”

A twentiethA twentiethcentury century exception exception to the to theorist/ the theorist/ experimenexperimentalisttalist dichotomy dichotomy waswas Enrico Enrico Fermi.

Fermi.

BornBorn in Italy in Italy in 1901, in 1901, his his earlyearly theoretical theoretical work work in quantum in quantum mechanics mechanics is essential is essential to chemists’ to chemists’ understanding understanding of the of the periodic periodic tabletable and and to the to the physics physics of neutrinos. of neutrinos.

But But he also he also did did crucial crucial experiments experiments in in nuclear nuclear physics, physics, for which for which he was he was awarded awarded the the Nobel Nobel Prize Prize in 1938. in 1938.

He and He and his wife, his wife, Laura Laura Fermi, Fermi, wentwent to Stockholm to Stockholm to reto receiveceive the the prize, prize, but but did did not not return return to Italy. to Italy.

Instead, Instead, fearing fearing persecution persecution in fascist in fascist ItalyItaly as Laura as Laura waswas Jewish, Jewish, theythey contincontinued ued on toonthe to United the United States, States, he taking he taking a position a position at Columbia at Columbia University.

University.

His His experiments experiments at Columbia at Columbia and and laterlater at the at the University University of Chicago of Chicago werewere pivotal pivotal in the in the development development of of nuclear nuclear weapons weapons and and nuclear nuclear power. power.

His His students students included included many many of the of most the most important important theorists theorists and and experimentalists experimentalists of the of post– the post– World World WarWar II generation, II generation, but but nonenone exhibited exhibited his his combination combination of talents. of talents.

My car My pool car pool has has not only not only educated educated me about me about a range a range of exof experimental perimental issues issues but has but has helped helped keepkeep me honest, me honest, focused focused on on questions questions thatthat either either are driven are driven by experiment by experiment or can or can be adbe addressed dressed by experiment. by experiment.

A deAfacto de facto requirement requirement of membership of membership in this in this poolpool is the is ability the ability to explain to explain to each to each other other whatwhat we are we are doing. doing.

As we As make we make our our journey, journey, we will we will encounter encounter many many indi-individual vidual physicists, physicists, bothboth historical historical figures figures and and theorists theorists and and experimentalists experimentalists active active now.now.

We We willwill encounter encounter menmen and and women women fromfrom different different continents, continents, but but it is ithard is hard to avoid to avoid the the 14

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reality reality thatthat the the fieldfield has has beenbeen dominated dominated by men by men fromfrom a a handful handful of countries. of countries.

Some Some of our of our actors actors havehave harbored harbored offensive offensive views views along along racial, racial, ethnic, ethnic, or gender or gender lines. lines.

NeverNevertheless, theless, I doIbelieve do believe the evidence the evidence is strong is strong thatthat the questions the questions we will we will encounter encounter are of areinterest of interest across across the lines the lines thatthat somesometimes times separate separate us, and us, and I hope I hope sharing sharing these these can can helphelp bring bring us together. us together.

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he arena he arena for our for our day-dayto- day to- day lives— lives— and and for exploring for exploring the the realms realms of the of very the very largelarge and and the very the very small— small— is normally is normally described described in terms in terms of space of space and and time.time.

“I’m“I’m sorry, sorry, I’m running I’m running late,”late,” we text. we text.

“LA “LA is three is three hours hours behind behind NewNew York,York, isn’tisn’t it?” or it?” or we might we might say, say, “Mt.“Mt. Everest Everest is only is only about about five fi miles ve miles high,high, right?” right?”

We all Wehave all have somesome working working intuition intuition for the for reality the reality of space of space and and time.time.

But But the laws the laws of nature of nature givegive a sharper a sharper meaning meaning to space to space and and timetime themselves. themselves.

IsaacIsaac Newton Newton (1643– (1643– 1727) 1727) was was a complex a complex person, person, and and his his scientific scientific evolution evolution waswas equally equally complex. complex.

His His father father dieddied shortly shortly before before his birth, his birth, and,and, as a as child, a child, he was he was for afor time a time abanabandoned doned by his by mother. his mother.

He was He was a diffi a diffi cult,cult, hot-tempered hot-tempered individindividual ual whowho formed formed few few lasting lasting relationships. relationships.

He had He had strong strong religious religious views views and and dabbled dabbled at various at various points points in his in life his with life with alchemy. alchemy.

In his In later his later years, years, he left he Cambridge left Cambridge for London for London and and largely largely gavegave up his up scientifi his scientifi c researches c researches to become to become Master Master of of 17

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the Mint. the Mint.

He secured He secured this this finalfiposition nal position through through friends. friends.

What What might might havehave beenbeen a sinecure a sinecure became became his passion. his passion.

He pursued He pursued new,new, better better standardized standardized coinage, coinage, but especially but especially threw threw his enerhis energies gies into into the investigation the investigation (often (often undercover), undercover), arrest, arrest, and and execuexecutiontion of counterfeiters— of counterfeiters— typically typically by hanging, by hanging, drawing, drawing, and and quartering. quartering.

It is Itfrom is from Newton, Newton, moremore thanthan his predecessors his predecessors or even or even his his mostmost notable notable contemporaries, contemporaries, thatthat we acquire we acquire the notion the notion thatthat the phenomena the phenomena we witness we witness in nature in nature are governed are governed by laws, by laws, and and thatthat these these lawslaws can can be expressed be expressed in precise, in precise, mathematical mathematical terms. terms.

He framed He framed his questions his questions in language in language shaped shaped by the by the worldviews worldviews of his ofage. his age.

He was He was influenced, influenced, certainly, certainly,

by Galileo,

by Galileo, but but alsoalso by his by competition his competition withwith somesome of his of contemporaries, his contemporaries, mostmost notably notably the English the English scientist scientist Robert Robert Hooke.

Hooke.

Their Their rivalry rivalry was was quitequite fierce. fierce.

Hooke Hooke felt, felt, possibly possibly unjustly, unjustly, thatthat Newton Newton stolestole his law his of lawgravitation of gravitation fromfrom him.him.

Newton Newton rejected rejected any any suchsuch insinuation. insinuation.

He famously He famously said,said, of his ofown his own accomplishments, accomplishments, in in a letter a letter to Hooke: to Hooke: “If I “If have I have seenseen further further it is it byisstanding by standing on the on the shoulders shoulders of giants.” of giants.”

ThisThis storystory is often is often told told as an asillustration an illustration of scientifi of scientifi c modesty, c modesty, but but as one as one of my of astronomy my astronomy colleagues colleagues explained explained to me, to me, Hooke Hooke was was quitequite slight slight (he actually (he actually described described himhim as a as dwarf, a dwarf, but this but this apparently apparently was was not true). not true).

While While somesome of my of my colleagues colleagues think think pretty pretty highly highly of themselves, of themselves, few few are are quitequite so cruel— so cruel— oftenoften quitequite the opposite. the opposite.

Newton, Newton, at various at various stages stages in his incareer, his career, worked worked in chemistry in chemistry and and on phenomena on phenomena connected connected withwith light.light.

He observed He observed correctly correctly thatthat white white lightlight is composed is composed of light of light of diff of erent different colors, colors, but he but he not not so correctly so correctly theorized theorized thatthat lightlight consisted consisted of particles, of particles, or or

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“corpuscles.” “corpuscles.”

For the For questions the questions thatthat concern concern us, Newton’s us, Newton’s invesinvestigations tigations understanding understanding the the motion motion of the of the planets planets and and the the moon moon are central. are central.

Newton Newton andand the the Character Character of Physical of Physical LawLaw The The title title of this of this section section is taken, is taken, withwith apologies, apologies, fromfrom a seta of set of lectures lectures given given in 1964 in 1964

by Richard

by Richard Feynman.

Feynman.

We speak We speak casually casually of physical of physical law, law, or laws or laws of nature, of nature, but but Feynman Feynman asked: asked: What What do we domean we mean by this? by this?

OurOur modern modern scientifi scientifi c paradigm c paradigm for physfor physical ical law law comes comes fromfrom Newton’s Newton’s lawslaws of motion of motion and and his law his law of of gravity. gravity.

Newton’s Newton’s successful successful application application of his of rules his rules and and tech-techniques niques to the to motion the motion of objects of objects in the in solar the solar system system was was the fithe rstfirst greatgreat triumph triumph of this of this worldview. worldview.

We may We may imagine imagine Newton Newton as heasdescribed he described himself, himself, sitting sitting in in a garden a garden and and watching watching the the fall fall of an of apple. an apple.

From From a modern a modern perspective, perspective, we can we can divide divide Newton’s Newton’s lawslaws into into two two types. types.

The The firstfiwere rst were his laws his laws of motion, of motion, a basic a basic framework, framework, a setaof setrules of rules applicable applicable to a to broad a broad array array of physical of physical phenomena. phenomena.

The The firstfirst law law of motion of motion sayssays thatthat a body a body in motion in motion remains remains in the in same the same statestate of motion of motion (it moves (it moves withwith the same the same speed, speed, or velocity) or velocity) un- unless less actedacted on by onaby force. a force.

ThisThis maymay seemseem intuitively intuitively reasonable, reasonable, but begs but begs the question: the question: What’s What’s a force? a force?

Newton Newton provided provided a defi a -definition, nition, through through his second his second law:law: A force A force givesgives rise rise to antoaccelan acceleration, eration, a change a change in speed, in speed, or velocity. or velocity.

ThisThis law law sayssays that,that, for for an object, an object, say say a car, a car, of aofgiven a given mass, mass, the the acceleration acceleration getsgets larger larger if the if force the force is larger. is larger.

For For a given a given amount amount of force, of force, the the

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acceleration acceleration is smaller is smaller if the if mass the mass is larger. is larger.

So, for So, the for same the same force, force, my Prius my Prius C accelerates C accelerates much much moremore rapidly rapidly thanthan a large a large truck. truck.

Similarly, Similarly, if I press if I press the gas the and gas and double double the force the force of the of the engine, engine, the particle the particle accelerates accelerates to highway to highway speeds speeds twice twice as fast. as fast.

These These two two rulesrules account account for the for motion the motion of things— of things— day-dayto-day to-day objects objects like like tennis tennis balls, balls, bullets, bullets, and and missiles, missiles, but but alsoalso enor-enormous mous bodies bodies like like planets, planets, stars,stars, and and galaxies. galaxies.

Having Having established established this this framework framework for motion for motion in space in space and and timetime (what (what is called is called kinematics), kinematics), Newton Newton tooktook another another crucial crucial step,step, determining determining the force the force of gravity. of gravity.

Humans Humans had had observed observed the motion the motion of the of planets the planets sincesince ancient ancient times. times.

In the In century the century before before Newton, Newton, a more a more precise precise picture picture had had developed developed of planof planetaryetary motion. motion.

The The sixteenthsixteenthcentury century Danish Danish astronomer astronomer Tycho Tycho Brahe Brahe (1546– (1546– 1601)1601) did did careful, careful, accurate accurate measurements measurements of the of the planetary planetary orbits orbits in aninobservatory an observatory funded funded by the by king the king of Denof Denmark. mark.

His His measurements measurements werewere particularly particularly remarkable remarkable as he as he did did not not havehave a telescope, a telescope, instead instead relying relying on instruments on instruments of of ancient ancient origin, origin, the sextant the sextant and and the quadrant, the quadrant, to measure to measure the the positions positions of planets of planets and and starsstars in the in sky. the sky.

Johannes Johannes Kepler Kepler (1571– (1571– 1630), 1630), Brahe’s Brahe’s assistant, assistant, analyzed analyzed the data, the data, summarizing summarizing it init in threethree “laws.” “laws.”

OneOne characterized characterized the shape the shape of the of orbits. the orbits.

A secA second ond governed governed the speeds the speeds of the of planets the planets as they as they move move through through theirtheir orbits. orbits.

A third A third related related the length the length of their of their year,year, the time the time it it takestakes themthem to complete to complete an orbit, an orbit, to their to their distance distance fromfrom the sun. the sun.

These These rulesrules werewere remarkable remarkable in that in that theythey didn’t didn’t correspond correspond to to any any obvious obvious intuition intuition and and theythey wentwent against against Kepler’s Kepler’s prejudices prejudices at the at start the start of the of project. the project.

TheyThey are also are also remarkable remarkable in the in care the care theythey show. show.

Kepler Kepler could could havehave declared declared the orbits the orbits to betocircles, be circles,

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and,and, in fact, in fact, the the shape shape of the of the orbits orbits of all of the all the planets planets thenthen known known are nearly are nearly circles, circles, but but not not quite; quite; theythey are actually are actually el- ellipses. lipses.

Before Before the demotion the demotion of Pluto of Pluto fromfrom its status its status as planet as planet to to dwarf dwarf planet, planet, I liked I liked to remark to remark to my to students my students thatthat it was it was the the onlyonly planet planet whose whose orbitorbit was was not very not very nearly nearly circular. circular.

I put I put lawslaws in quotes in quotes above above because because Kepler’s Kepler’s pronouncepronouncements, ments, while while providing providing a way a way of organizing of organizing Tycho Tycho Brahe’s Brahe’s ob- observations, servations, werewere not laws not laws in the in sense the sense of the of laws the laws thatthat Newton Newton would would promulgate. promulgate.

The The difference difference is subtle is subtle and and beautiful. beautiful.

The The firstfielement rst element of this of this distinction distinction has has to dotowith do with the broad the broad appliapplicability cability of Newton’s of Newton’s laws.laws.

The The lesson lesson of the of story the story of Newton of Newton and and the apple, the apple, apocryphal apocryphal or not, or not, is not is about not about howhow Newton Newton discovered discovered objects objects fall down. fall down.

It is It hisisrealization his realization that that the force the force of gravity of gravity is universal, is universal, that that the the moon, moon, in particular, in particular, fallsfalls toward toward the earth the earth according according to the tosame the same rulerule thatthat the apple the apple fallsfalls toward toward the earth, the earth, as does as does the earth the earth to- towardward the sun. the sun.

He translated He translated this this into into the statement the statement that that the force, the force, say between say between the sun the sun and and a planet, a planet, is proportional is proportional to the to mass the mass of of the sun, the sun, times times the mass the mass of the ofplanet, the planet, divided divided by the bysquare the square of the of the distance distance between between them. them.

ThisThis means, means, for example, for example, sincesince Venus Venus has ahas mass a mass similar similar to that to that of the of earth the earth but is but closer is closer to the to sun— the sun— about about 62 million 62 million miles miles as compared as compared to 98tomillion—the 98 million—the pullpull of the of sun the sun is roughly is roughly twice twice as large as large on Venus on Venus as on asthe on earth. the earth.

Correspondingly, Correspondingly, Venus Venus moves moves much much faster faster thanthan earth earth in its in its orbit, orbit, while while the outer the outer planets planets move move moremore slowly. slowly.

The The forceforce of of gravity gravity the earth the earth exerts exerts on the on apple the apple is smaller is smaller thanthan it exerts it exerts on on the moon the moon sincesince the apple the apple has far hasless far less mass, mass, and and it would it would not be not be appreciable appreciable werewere it not it for notthe for much the much shorter shorter distance distance fromfrom the the

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center center of the of earth the earth to the to apple the apple compared compared to the to moon. the moon.

WithWith this this law law for the for force, the force, Newton Newton could could explain, explain, indeed, indeed, all three all three of Kepler’s of Kepler’s laws.laws.

But Newton’s But Newton’s lawslaws werewere much much moremore powerful powerful thanthan Kepler’s, Kepler’s, making making much much moremore precise precise predictions. predictions.

Newton Newton realized realized thatthat the orbits the orbits are not are exactly not exactly ellipses. ellipses.

The The planets planets are are pulled pulled on not on only not only by the by sun the sun but by butthe by other the other planets planets and and theirtheir moons moons as well. as well.

Because Because the planets the planets are much are much smaller smaller thanthan the the sun,sun, thesethese effects effects are small, are small, but Newton’s but Newton’s workwork opened opened up the up the possibility possibility of a of fara more far more detailed detailed study study of planetary of planetary motion, motion, which which continues continues to this to this day. day.

It was It was not until not until two two centuries centuries laterlater thatthat Einstein, Einstein, withwith his theory his theory of general of general relativity, relativity, predicted predicted tiny tiny breakings breakings of the of law, the law, which which werewere conficonfi rmedrmed by experiment. by experiment.

Returning Returning to the to distinction the distinction between between Kepler Kepler and and Newton, Newton, Kepler’s Kepler’s lawslaws summarized summarized regularities regularities he observed he observed in data. in data.

TheyThey werewere not exact not exact (though (though he likely he likely believed believed so), and, so), and, moremore importantly, importantly, Kepler Kepler could could not say, not say, a priori, a priori, just just howhow precise precise his his rulesrules should should be. Newton be. Newton could could explain explain the small the small violations violations of of Kepler’s Kepler’s rules. rules.

Einstein’s Einstein’s relativity relativity principles principles enlarged enlarged and and tran-transcended scended bothboth Newton’s Newton’s lawslaws of motion of motion and and his law his law of gravity, of gravity, and and would would allow allow himhim to say to say when when Newton’s Newton’s lawslaws should should be be validvalid and and when when theythey would would not apply. not apply.

These These issues issues aside, aside, Newton’s Newton’s kinematic kinematic framework framework became became the bedrock the bedrock of a of range a range of technologies. of technologies.

EvenEven when when the underlythe underlying ing forces forces could could not not be described be described in asinsimple as simple a way a way as the as the forceforce of gravity of gravity between between the the sun sun and and the the planets, planets, problems problems ranging ranging fromfrom civilcivil engineering engineering challenges challenges to motion to motion of projecof projectilestiles (artillery (artillery shells, shells, missiles), missiles), features features of weather, of weather, and and much, much, much much moremore could— could— and and still still can— can— be described be described in terms in terms of of Newton’s Newton’s lawslaws of motion. of motion.

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