The Manga Guide Relativity - No Starch Press

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Th e M a n g a G u i de to PRaise for the manga guide series“Stimulus for the next generation of scientists.” — Scientific computing“A great fit of FOrm and subject. Recommended.” — Otaku USA MagazineEverything’s gone screwy at Takai Academy.The Manga Guide to Relativity alsoWhen the crazy headmaster forces Minagi’steaches you how to:entire class to study Einstein’s theoryUnderstand and useof relativity over summer school, MinagiE mc ², the world’smost famous equationvolunteers to go in their place. There’sjust one problem: He’s never even heardCalculate the effects of time dilationof relativity before! Luckily, Minagi has theusing the Pythagorean theoremplucky Miss Uraga to teach him.follow along withUnderstand classic thought experimentsThe Manga Guidelike the Twin Paradox, and see whyto Relativity as Minagi learns about thelength contracts and mass increasesnon-intuitive laws that shape our universe.at relativistic speedsBefore you know it, you’ll master difficultHideo NittaMasafumi YamamotoKeita TakatsuTrend-Pro Co., Ltd .Grasp the underpinnings of Einstein’sconcepts like inertial frames of reference, unified space-time, and the equivalencespecial and general theories of relativityIf the idea of bending space and time reallyaffects modern astronomy and discoverwarps your brain, The Manga Guide toRelativity will straighten things out.why GPS systems and other everyday technologies depend on Einstein’s extraordinarydiscovery.T H E F I N E ST I N G E E K E N T E RTA I N M E N T 19.95( 22.95 CDN)nitta,Yamamoto, takatsu,trend-PROprinciple. You’ll even see how relativityw w w.nostarch.comRelativity A Charming Cartoon Guide toThe Theory of Relativitythe manga guide to Relativity“Highly Recommended.” — Choice MagazineComicsinside!shelve in: SCIENCE/Physics/Relativity“ I L I E F L AT .”This book uses a lay-flat binding that won't snap shut.Find more Manga Guides at www.edumanga.me44055 COV.indd 14405511-03-2321:29:52cov1Cyan, Magenta, Yellow, Black11-03-17 9:41 AM

The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.

Praise for the Manga Guide series“Highly recommended.”—choice magazine on the manga guide to databases“Stimulus for the next generation of scientists.”— scientific computing on the manga guide to molecular biology“A great fit of form and subject. Recommended.”— otaku usa magazine on the manga guide to physics“The art is charming and the humor engaging. A fun and fairly painless lesson on whatmany consider to be a less-than-thrilling subject.”— school library journal on the manga guide to statistics“This is really what a good math text should be like. Unlike the majority of books onsubjects like statistics, it doesn’t just present the material as a dry series of pointlessseeming formulas. It presents statistics as something fun, and something enlightening.”— good math, bad math on the manga guide to statistics“I found the cartoon approach of this book so compellingand its story so endearing that I recommend that everyteacher of introductory physics, in both high school andcollege, consider using it.”— american journal of physics on the manga guide to physicsWow!“A single tortured cry will escape the lips of every thirtysomething biochem major who sees The Manga Guide toMolecular Biology: ‘Why, oh why couldn’t this have beenwritten when I was in college?’”—the san francisco examiner“A lot of fun to read. The interactions between the characters are lighthearted, and the whole setting has a sortof quirkiness about it that makes you keep reading just forthe joy of it.”— hack a day on the manga guide to electricity“The Manga Guide to Databases was the most enjoyabletech book I’ve ever read.”— rikki kite, linux pro magazine“For parents trying to give their kids an edge or justfor kids with a curiosity about their electronics, TheManga Guide to Electricity should definitely be on theirbookshelves.”— sacramento book reviewThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 13/15/2011 3:25:43 PM

“This is a solid book and I wish there were more like it in the IT world.”—slashdot on the manga guide to databases“The Manga Guide to Electricity makes accessible a very intimidating subject, letting thereader have fun while still delivering the goods.”— geekdad blog, wired.com“If you want to introduce a subject that kids wouldn’t normally be very interested in, give itan amusing storyline and wrap it in cartoons.”— make on the manga guide to statistics“This book does exactly what it is supposed to: offer a fun, interesting way to learn calculusconcepts that would otherwise be extremely bland to memorize.”— daily tech on the manga guide to calculus“The art is fantastic, and the teaching method is both fun and educational.”— active anime on the manga guide to physics“An awfully fun, highly educational read.”— frazzleddad on the manga guide to physics“Makes it possible for a 10-year-old to develop a decent working knowledge of a subjectthat sends most college students running for the hills.”— skepticblog on the manga guide to molecular biology“This book is by far the best book I have read on the subject. I think this book absolutelyrocks and recommend it to anyone working with or just interested in databases.”— geek at large on the manga guide to databases“The book purposefully departs from a traditional physics textbook and it does it very well.”— dr. marina milner-bolotin, ryerson university on the manga guide to physics“Kids would be, I think, much more likely to actually pick this up and find out if they areinterested in statistics as opposed to a regular textbook.”— geek book on the manga guide to statistics“The Manga Guide to Statistics offers a visualization of statistics that can’t be found in anymere textbook.”— anime 3000“A great introduction for readers of any age, and an exemplar of technical communication.”— linux users of victoria on the manga guide to electricityThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 23/15/2011 3:25:43 PM

The Manga Guide to RelativityThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 33/15/2011 3:25:43 PM

The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 43/15/2011 3:25:43 PM

The Manga Guide toRELATIVITYHideo NittaMasafumi YamamotoKeita TakatsuTrend-pro Co., Ltd.The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 53/15/2011 3:25:43 PM

The Manga Guide to Relativity.Copyright 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.The Manga Guide to Relativity is a translation of the Japanese original, Manga de wakaru soutaiseiriron, published byOhmsha, Ltd. of Tokyo, Japan, 2009 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.This English edition is co-published by No Starch Press, Inc. and Ohmsha, Ltd.All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronicor mechanical, including photocopying, recording, or by any information storage or retrieval system, without the priorwritten permission of the copyright owner and the publisher.15 14 13 12 11   1 2 3 4 5 6 7 8 9ISBN-10: 1-59327-272-3ISBN-13: 978-1-59327-272-2Publisher: William PollockSupervising Editor: Hideo NittaAuthor: Masafumi YamamotoIllustrator: Keita TakatsuProducer: TREND-PRO Co., Ltd.Production Editor: Serena YangDevelopmental Editor: Tyler OrtmanTranslator: Arnie RusoffTechnical Reviewers: David Issadore and John RoederCompositor: Riley HoffmanCopyeditor: Paula L. FlemingProofreader: Serena YangIndexer: Sarah SchottFor information on book distributors or translations, please contact No Starch Press, Inc. directly:No Starch Press, Inc.38 Ringold Street, San Francisco, CA 94103phone: 415.863.9900; fax: 415.863.9950; [email protected]; http://www.nostarch.com/Library of Congress Cataloging-in-Publication DataNitta, Hideo, 1957[Manga de wakaru soutaiseiriron. English]The manga guide to relativity / Hideo Nitta, Masafumi Yamamoto, Keita Takatsu ; Trend-pro Co., Ltd. -- English ed.p. cm.Includes index.ISBN-13: 978-1-59327-272-2ISBN-10: 1-59327-272-31. Relativity (Physics)--Comic books, strips, etc. 2. Graphic novels. I. Yamamoto, Masafumi, 1947- II. Takatsu,Keita. III. Trend-pro Co. IV. Title.QC173.57.N5813 2010530.11--dc222010038111No Starch Press and the No Starch Press logo are registered trademarks of No Starch Press, Inc. Other product andcompany names mentioned herein may be the trademarks of their respective owners. Rather than use a trademarksymbol with every occurrence of a trademarked name, we are using the names only in an editorial fashion and to thebenefit of the trademark owner, with no intention of infringement of the trademark.The information in this book is distributed on an “As Is” basis, without warranty. While every precaution has beentaken in the preparation of this work, neither the author nor No Starch Press, Inc. shall have any liability to any personor entity with respect to any loss or damage caused or alleged to be caused directly or indirectly by the informationcontained in it.All characters in this publication are fictitious, and any resemblance to real persons, living or dead, is purely coincidental.The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 63/15/2011 3:25:43 PM

Table of ContentsPreface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ixPrologue: Outrageous closing ceremony . . . . . . . . . . . . . . . . . . . . . . . . . 11What Is Relativity? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91. What Is Relativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Galilean Principle of Relativity and Newtonian Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Mystery of the Speed of Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. Einstein Discarded Newtonian Mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .What Is Light? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Light Is Constant (and They Prove It Every Day in a Lab Called SPring-8) . . . . . . . . . . . . . . . . .What’s Simultaneous Depends on Whom You Ask! (Simultaneity Mismatch) . . . . . . . . . . . . . . . .Case of Newtonian Velocity Addition (Nonrelativistic Addition) . . . . . . . . . . . . . . . . . . . . . . .Case in Which the Speed of Light Is Constant (Relativistic Addition of Velocity) . . . . . . . . . .Galilean Principle of Relativity and Galilean Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Differences Between the Galilean Principle of Relativity and Einstein’s Special Principle ofRelativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Wait a Second—What Happens with the Addition of Velocities? . . . . . . . . . . . . . . . . . . . . . . . . . .1417233440434444464748482What Do You Mean, Time Slows Down? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511. Urashima Effect (Time Dilation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Why Does Time Slow Down? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. The Slowing of Time Mutually Affects Each Party Equally . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. Looking at the Slowing of Time Using an Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Using the Pythagorean Theorem to Prove Time Dilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .How Much Does Time Slow Down? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5456647378803The Faster an Object moves, the Shorter and Heavier It Becomes? . . . . 831. Does Length Contract When You Go Faster? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 862. Do You Get Heavier When You Go Faster? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92Using an Equation to Understand Length Contraction (Lorentz Contraction) . . . . . . . . . . . . . . . 106Muons with Extended Life Spans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108Mass When Moving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109Galilean Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109Newton’s Second Law of Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109Lorentz Transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Relationship Between Energy and Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112Does Light Have Zero Mass? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 73/15/2011 3:25:43 PM

4What Is General Relativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1151. Equivalence Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2. Light Is Bent by Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3. Time Is Slowed Down by Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. Relativity and the Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .The Slowing of Time in General Relativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .The True Nature of Gravity in General Relativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Phenomena Discovered from General Relativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Bending of Light (Gravitation Lensing) Near a Large Mass (Such as the Sun) . . . . . . . . . .Anomalous Perihelion Precession of Mercury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Black Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Global Positioning System and Relativity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .120133143149158162162162164164165Epilogue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175viii Table of ContentsThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 83/15/2011 3:25:43 PM

PrefaceWelcome to the world of relativity!Everyone wonders what relativity is all about. Because the theory of relativity predictsphenomena that seem unbelievable in our everyday lives (such as the slowing of time andthe contraction of the length of an object), it can seem like mysterious magic.Despite its surprising, counterintuitive predictions, Einstein’s theory of relativity has beenconfirmed many times over with countless experiments by modern physicists. Relativity andthe equally unintuitive quantum mechanics are indispensable tools for understanding thephysical world.In Newton’s time, when physicists considered velocities much smaller than the speedof light, it was not a problem to think that the measurement of motion, that is, space andtime, were independent, permanent, and indestructible absolutes. However, by the end ofthe 19th century, precise measurements of the speed of light combined with developmentsin the study of electromagnetism had set the stage for the discovery of relativity. As a result,time and space, which had always been considered to be independent and absolute, had tobe reconsidered.That’s when Einstein arrived on the scene. Einstein proposed that time and space werein fact relative. He discarded the idea that space and time were absolute and considered thatthey vary together, so that the speed of light is always constant.This radical insight created a controversy just as Galileo’s claim that Earth orbited theSun (and not vice versa) shocked his peers. However, once we ventured into space, it wasobvious that Earth was indeed moving.In a similar way, relativity has given us a more accurate understanding of conceptsregarding the space-time in which we are living. In other words, relativity is the result ofasking what is actually happening in our world rather than saying our world should be aparticular way.Although this preface may seem a little difficult, I hope you will enjoy the mysteries ofrelativity in a manga world together with Minagi and his teacher, Miss Uraga. Finally, I’d liketo express my deep gratitude to everyone in the development bureau at Ohmsha; re akino,who toiled over the scenario; and Mr. Keita Takatsu, who converted it into such an interesting manga.Well, then. Let’s jump into the world of relativity.Masafumi YamamotoJune 2009The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 93/15/2011 3:25:43 PM

The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 103/15/2011 3:25:43 PM

PROLOGUEoutrageous closingceremonyThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 13/15/2011 3:25:44 PM

The school isbrimming with anticipation of swimming atthe beach.camping.and summerlove.Taigai Academy,the last dayof schoolbeforesummerI realize thatyour summervacation is aboutto begin.Therefore!I'm giving this year'sjunior class a specialpresent so that youcan enjoy your summerbreak even more.HeadmasterRase IyagaWhat's he trying topull? The headmasteris such a creep!2prologueThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 23/15/2011 3:25:45 PM

And hereit is!The Wheel of Destiny!Your fate is nowin my hands!EnglishMathFreearchr es enoneRelativityWHAT?!This summer, you'llhave the opportunityto study whicheversubject the dart hits.Do you understand?He's got to bekidding!If Yashiki throws,he'll surely hit"None" since he'sthe star pitcher.Okay.Here we go!N-no way! Wait!hehhehThat's right! Surely,if "Windmill Yashiki"does it.whirrROh no!Headmaster Iyagawill be doing it!outrageous closing ceremony3The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 33/15/2011 3:25:46 PM

That's devious,headmaster!It's tyranny!And What the heckis relativity?.!!RelativityWhat the.?!What'sthis.the worst one!What is that?!the VicePrincipal ishere!RelativityMath!Woof!fWooEnglishIs he messingwith us?!Vice PrincipalKoromaru4 prologueThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 43/15/2011 3:25:48 PM

We can't understandthe vice principal, Buthe looks angry at theheadmaster!What?Vice Principal, you'vealready told themabout this, right?GrrrrWhy is a dog the viceprincipal aroundhere, anyway?Hey, you can't justspring this on us!Good gracious! It'sYou, student bodypresident so-and-so.The wheel of destinyis a farce! You're justtormenting us.Everyone has madetheir plans for summervacation already!Student bodypresidentRuka MinagiThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 53/15/2011 3:25:49 PM

Oh really? Well,shall I have youstudy relativity asa representative ofall students?Wha-what?!If you do that, thenthe other studentswill be exempt.Bu-but what isrelativity?!Hey, if we leave it up toMinagi, we'll be able toenjoy summer vacation,won't we?Can we really dosuch a terriblething to him?It seems like you'vegot a head start!Ack!Ack!Er.Um.If it's okaywith you, I couldteach you aboutrelativity.6 prologueThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 63/15/2011 3:25:50 PM

You probablywouldn't wantme to teachhim, wouldyou.?Physics teacherAlisa UragaComeon man!Saveus!Webegyou,man.Well, What willit be, Minagi?We can discussthat later!Okay, Iaccept yourchallenge!!!doit!Bleh.outrageous closing ceremony7The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 73/15/2011 3:25:51 PM

All right then. Whensummer vacation isover, submit a reporton relativity.And if you can'tdo it.I don't careif Miss Uragateaches you,but you have towrite the reportyourself!Okay!If I can't do it.?You'll spendyour senioryear as my.personalsecretary!No freakingway!This is crazy!I'll do it!WOOF!teeheeThe Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 83/15/2011 3:25:52 PM

What Is Relativity?The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 93/15/2011 3:25:52 PM

Ah, I was a bigbraggart, but nowI've got to do it.chirpchirpAt least I'll begetting privatelessons from theintriguing Miss Uraga!PhysicsRoomHmmm.Oh, here it is.You'relate!!!WHAM!The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 103/15/2011 3:25:53 PM

Miss Uraga.?!It's outrageousthat you arrivedlater than I did.Do you have theflexible hoursof an executive?mi. na. gi.It's probablynormal, but youreyes.are theyblack holes?SLAPSLAPwh-whwhat?psh, I'm sorry, I didn'tmean to be so severe.she's kidding?!Seriously, though,Please don't comelate again.What is relativity?11The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 113/15/2011 3:25:54 PM

That was mydisciplinarian face!Adults must use itevery so often.Our image of you.That freak of aheadmaster gave me animpossible task.This is awful.it's summervacation.now, don't be sopessimistic.Honestly, when hestarted talking aboutrelativity, I thoughtthat this was my bigopportunity!What do you mean byopportunity?12Chapter 1The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 123/15/2011 3:25:55 PM

And if I got a high evaluationfor being "Miss Uraga whoenthusiastically providesguidance to students," I'deventually become the nextheadmistress.It's my field ofspecialty. I thoughtI could use thissituation to rackup points with theheadmaster.That's a bitfar-fetched,isn't it?I'm just yoursteppingstone, huh?Well, let's get started!First, since you've askedwhat relativity is.Okay.What Is Relativity?13The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 133/15/2011 3:25:57 PM

1. What is relativity?GeneralSpecialGeneral relativityextended specialrelativity.wspoaShouldn't ageneral theorycome before aspecialized one?There are two types ofrelativity. One is specialrelativity, and the other isgeneral relativity.Special relativity is "special"because it is a simplification ofGeneral Relativity and is only true inthe special cases when the effectsof gravity and acceleration can besafely ignored.General relativityObserverObserverSpecial relativityGeneral relativity is a broadertheory of relativity thataccounts for the effects ofboth acceleration and gravity.Is it simplerwhen gravity oracceleration is notconsidered?14Well,sure it is.Chapter 1The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 143/15/2011 3:25:58 PM

The theory ofrelativity says that thepassage of time, distance, andmass depend on the motion ofwhoever makes the observation. Inspecial relativity, we only considerobservers at rest or who move ata constant velocity. We call thisvantage point an inertialreference frame.When observationsare made by an observerundergoing acceleration,that is called makingobservations from a noninertial reference frame,and we must use generalrelativity. Let me explainwhat these theoriesbroadly mean.Slows down,contracts?!Do those thingsreally occur?!ct!traCon ease!rIncspecial relativitysays that forobjects in motion.time slows down,length contracts, andmass increases.nTrasmoerrphO!!s, G.It's not like you areimagining it.The effects ofrelativity onlybecome noticeableat speeds close tothe speed of light.These speeds areextremely fast, and sowe very rarely observerelativistic effects onearth.Whattheheck?What Is Relativity?15The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 153/15/2011 3:25:59 PM

Relativityflash!General relativity saysthat an object withmass creates gravity byaffecting time and space.I see.for example, light.What is gravity?Stars have so much mass thatthey distort space and timeenough that we can observelight bend as it passes by.p!BzzThe observation of lightbending as it passes by alarge star was actuallythe first confirmation ofthe theory of generalrelativity.Now, since generalrelativity is moreadvanced anddifficult.Okaaaay Because if I don'tunderstand, I'llreally be in hotwater.let's proceedby focusing ourdiscussion on specialrelativity. You shouldappreciate this.16Chapter 1The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 163/15/2011 3:26:00 PM

2. Galilean principle of relativity andNewtonian mechanicsHistoricalbackground?Let's begin with somehistorical backgroundso you can understandrelativity a little better.It will probably be easierfor you to understand ifI tell you how the theoryof relativity originated.by the way, since I'll glossover some details, I hopeyou'll forgive me if myexplanation lacks a littlescientific precision.First, more than 300years before Einsteinmade his appearance well, I guessit's okay aslong as I getthe generalidea. there was the GalileanPrinciple of Relativitydiscovered by Galileo Galilei.Relativity.principle?What Is Relativity?17The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 173/15/2011 3:26:01 PM

Minagi, you knowwhat uniformlinear motion is,don't you?Um, it means thatsomething ismoving with afixed speed anddirection?Ah.A mysteriouscreatureappeared!State of restIf there is noexternal force, anobject at rest willremain at rest.Huh?!State ofmoving with afixed speedand directionityativRel ckkiThe law of inertiatells us that in an inertialreference frame, an objectat rest will stay atrest and.An object that is moving at aconstant velocity will continuemoving, until acted upon by anoutside force.Help Meeeeeee!18Chapter 1The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 183/15/2011 3:26:02 PM

The Galilean Principle ofRelativity tells us that Newton'slaws are the same in any inertialreference frame that we mightchoose. In other words, nomatter where an observer is inthe universe or how fast she ismoving, the laws of physicswill never change.For example, if I tossa ball straight up in aplace that is at rest, itwill come back to myhand, right?I sort ofunderstand it.In the same way, if I tossa ball straight up in atrain that is moving at aconstant speed, it willalso return to my hand.In other words, it doesnot matter if you are atrest or if you are moving,the laws of physics behaveexactly the same.What Is Relativity?19The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 193/15/2011 3:26:03 PM

But if earth itself is inmotion through ourgalaxy, does that meanthat earth is a movingreference frame?What do youmean?That’s right! Because inrelativity, no referenceframe is preferable to anyother reference frame,even Earth itself cannot beconsidered an “absolute”frame of reference.ityclackclackclackclackDon't you feel thiswhen you're ridinga train?ityclackclackFor example, when train A,which is moving at 50 km/h,passes by train B, which ismoving at 50 km/h in theopposite direction.a person on the othertrain seems to you tobe moving at 100 km/h.I see. That's justthe way it seems.20 Chapter 1The Manga Guide to Relativity 2011 by Hideo Nitta, Masafumi Yamamoto, and TREND-PRO Co., Ltd.RELATIVITY 03.indb 203/15/2011 3:26:04 PM

This perceivedmotion is theresult of therelationshipbetween youand the otherparty.The earth and everyother object inthe universe arecontinuously movingrelative to each other.It is a wayof thinkingreferred toas "relative."It is only inour frame ofreference that weare considered tobe at rest.You considerthe movement ofthe object withyourself as thereference point,right?Mmmhmmm.You assume that you ar

—rikki kite, linux pro magazine “For parents trying to give their kids an edge or just for kids with a curiosity about their electronics, The Manga Guide to Electricity should definitely be on their bookshelves.” —sacramento book review Wow! RELATIVITY_03.indb 1 3/15/2011