motionmountain-part5 (pdf document) free file download at fliiby.com

"Christoph Schiller MOTION MOUNTAIN the adventure of physics pleasure, technology and stars www.motionmountain.eu Christoph Schiller Motion Mountain The Adventure of Physics Pleasure, Technology and Stars available free of charge at www.motionmountain.eu Editio vicesima secunda. Proprietas scriptoris © Christophori Schiller secundo anno Olympiadis vicesimae nonae. Omnia proprietatis iura reservantur et vindicantur. Imitatio prohibita sine auctoris permissione. Non licet pecuniam expetere pro aliquo, quod partem horum verborum continet; liber pro omnibus semper gratuitus erat et manet. Twenty-second edition, second printing, ISBN 978-300-021946-7. Copyright © 2009 by Christoph Schiller, the second year of the 29th Olympiad. This pdf file is licensed under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 Germany Licence, whose full text can be found on the website creativecommons.org/licenses/by-nc-nd/3.0/de, with the additional restriction that reproduction, distribution and use, in whole or in part, in any product or service, be it commercial or not, is not allowed without the written consent of the copyright owner. The pdf file was and remains free for everybody to read, store and print for personal use, and to distribute electronically, but only in unmodified form and at no charge. To Esther and Britta τῷ ἐμοὶ δαὶμονι Die Menschen stärken, die Sachen klären. Preface The present overview of everyday physics is the result of a threefold aim I have pursued since 1990: to present the basics of motion in a way that is simple, up to date and vivid. In order to be simple, the text focuses on concepts, while keeping mathematics to the necessary minimum. Understanding the concepts of physics is given precedence over using formulae in calculations. The whole text is within the reach of an undergraduate. Within physics, quantum theory is the description of motion based on a smallest action, or better, a smallest change in nature. With this basic idea, we show how to describe life, death and pleasure. A smallest change explains the observations of chemistry, geology, material science and the working of the stars. These topics, corresponding to the three points labelled ‘quantum physics’ in Figure 1, are explored in the following. In order to be up to date, the text is enriched by the many gems – both theoretical and empirical – that are scattered throughout the scientific literature. In order to be vivid, the text tries to startle the reader as much as possible. Reading a book on general physics should be like going to a magic show. We watch, we are astonished, we do not believe our eyes, we think, and finally – maybe – we understand the trick. When we look at nature, we often have the same experience. The text tries to intensify this by following a simple rule: on each page, there should be at least one surprise or provocation for the reader to think about. Numerous interesting challenges are proposed. Hints or answers to these are given in an appendix. Giving full rein to one’s curiosity and thought leads to the development of a strong and dependable character. The motto of the text, die Menschen stärken, die Sachen klären, a famous statement by Hartmut von Hentig on pedagogy, translates as: ‘To clarify things, to fortify people.’ Exploring any limit requires courage; and courage is also needed to abandon space and time as tools for the description of the world. Changing habits of thought produces fear, often hidden by anger; but we grow by overcoming our fears. The great adventures in life allow this: exploring love is one, exploring physics is another. Eindhoven and other places, 8 January 2009 “ Primum movere, deinde docere.* Antiquity ” Motion Mountain – The Adventure of Physics available free of charge at www.motionmountain.eu Copyright © Christoph Schiller November 1997–January 2009 Advice for learners In my experience as a teacher, there was one learning method that never failed to transform unsuccessful pupils into successful ones: if you read a book for study, summarize every section you read, in your own words, aloud. If you are unable to do so, read the section again. Repeat this until you can clearly summarize what you read in your own * ‘First move, then teach.’ In modern languages, the mentioned type of moving (the heart) is often called motivating; both terms go back to the same Latin root. 8 preface PHYSICS: Describing motion with action. (Unified) theory of motion Adventures: understanding everything, intense fun with thinking, catching a glimpse of bliss What are space, time and quantum particles? General relativity Adventures: the night sky, measuring curved space, exploring black holes and the universe, space and time How do everyday, fast and large things move? Quantum theory with gravity Adventures: bouncing neutrons, understanding tree growth Quantum field theory Adventures: building accelerators, understanding quarks, stars, bombs and the basis of life, matter, radiation How do small things move? What are things? Motion Mountain – The Adventure of Physics available free of charge at www.motionmountain.eu Classical gravity Adventures: climbing, skiing, space travel, the wonders of astronomy and geology Special relativity Adventures: understanding time dilation, length contraction and E=mc2 c h, e, k Quantum theory Adventures: death, sexuality, biology, enjoying art, colours in nature, all high-tech business, medicine, chemistry, evolution G Galilean physics, electricity and heat Adventures: sport, music, sailing, cooking, using electricity and computers, understanding the brain and people F I G U R E 1 A complete map of physics: the connections are deﬁned by the speed of light c, the gravitational constant G, the Planck constant h, the Boltzmann constant k and the elementary charge e. Copyright © Christoph Schiller November 1997–January 2009 words, aloud. You can do this alone in a room, or with friends, or while walking. If you do this with everything you read, you will reduce your learning and reading time significantly. In addition, you will enjoy learning from good texts much more and hate bad texts much less. Masters of the method can use it even while listening to a lecture, in a low voice, thus avoiding to ever take notes. Using this book Text in green, as found in many marginal notes, is a link that can be clicked in a pdf reader. Green links can be bibliographic references, footnotes, cross references to other pages, challenge solutions or URLs of other websites. preface 9 Solutions and hints for challenges are given at the end of each part. Challenges are classified as research level (r), difficult (d), standard student level (s) and easy (e). Challenges of type r, d or s for which no solution has yet been included in the book are marked (ny). A request The text is and will remain free to download from the internet. In exchange, please send me a short email on the following issues: — What was unclear? — What story, topic, riddle, picture or movie did you miss? — What should be improved or corrected? Feedback on the specific points listed on the www.motionmountain.eu/help.html web page is most welcome of all. You can also add feedback directly to www.motionmountain. eu/wiki. On behalf of all other readers, thank you in advance for your input. For a particularly useful contribution you will be mentioned – if you want – in the acknowledgements, receive a reward, or both. But above all, enjoy the reading. Challenge 1 s Motion Mountain – The Adventure of Physics available free of charge at www.motionmountain.eu Copyright © Christoph Schiller November 1997–January 2009 Photo missing Pleasure, Technology and Stars In our quest to understand how things move as a result of a minimal change in nature, we discover that interactions are exchanges of radiation particles, why the floor does not fall but keeps on carrying us, why a smallest change is necessary to make pleasure possible, why empty space pulls mirrors together, why the stars shine, and why swimming and flying is not so easy. Contents 15 15 1 Motion for enjoying life Biological machines Reproduction 16 • Quantum machines 17 • How do we move? – Molecular motors 18 • Linear molecular motors 21 • Curiosities and fun challenges about biology 22 The physics of pleasure The nerves and the brain 30 • Living clocks 30 • When do clocks exist? 31 • The precision of clocks 32 • Why are predictions so difficult, especially of the future? 34 • Decay and the golden rule 34 • The present in quantum theory 35 • Why can we observe motion? 36 • Rest and the quantum Zeno effect 37 • Consciousness – a result of the quantum of action 37 • Why can we observe motion? – Again 38 • Curiosities and fun challenges about quantum experience 38 • Summary on pleasure 41 Changing the world with quantum theory Chemistry – from atoms to DNA Bonds 43 • Ribonucleic acid and deoxyribonucleic acid 45 • Curiosities and fun challenges about chemistry 46 Materials science Why does the floor not fall? 48 • Rocks and stones 49 • Some interesting crystals 49 • How can one look through matter? 56 • What is necessary to make matter invisible? 56 • The causes of colour 59 • How does matter behave at the lowest temperatures? 66 • Curiosities and fun challenges about materials science 67 Quantum technology Motion without friction – superconductivity and superfluidity 72 • The fractional quantum Hall effect 74 • Lasers and other spin-one vector boson launchers 79 • Can two photons interfere? 80 • Can two electron beams interfere? 81 • Challenges, dreams and fun curiosities about quantum technology 83 Q uantum electrodynamics – the origin of virtual realit y Ships, mirrors and the Casimir effect 85 • The Lamb shift 87 • The QED Lagrangian 88 • Interactions and virtual particles 88 • Vacuum energy 88 • Moving mirrors 88 • Photons hitting photons 89 • Is the vacuum a bath? 90 • Renormalization – why is an electron so light? 90 • Curiosities and fun challenges of quantum electrodynamics 91 • How can one move on perfect ice? – The ultimate physics test 96 • A summary of quantum electrodynamics 96 • Open questions in QED 98 Q uantum mechanics with gravitation – the first approach The phase of wave functions 100 • Playing table tennis with neutrons 100 • The gravitational Bohr atom 102 • Gravitation and limits to disorder 102 • Measuring acceleration with a thermometer – Fulling–Davies–Unruh radiation 103 • Black holes aren’t black 104 • Gamma ray bursts 107 • Material properties of black holes 109 • How do black holes evaporate? 110 • The information paradox of black holes 110 • More paradoxes 112 • Curiosities about quantum theory and gravity 112 • Quantum mechanics of gravitation 113 • Do gravitons exist? 114 • Space-time foam 114 • Decoherence of space-time 115 • Quantum theory as the enemy of science fiction 115 • No vacuum means no particles 116 • Summary on quantum theory and gravity 116 The structure of the nucleus – the densest clouds 27 42 42 2 48 72 85 3 100 4 118 5 contents 13 A physical wonder – magnetic resonance imaging 118 • The size of nuclei 120 • Nuclei are composed 123 • Nuclei can move alone – cosmic rays 125 • Nuclei decay 131 • Why is hell hot? 132 • Nuclei can form composites 133 • Nuclei have colours and shapes 134 • The four types of motion in the nuclear domain 135 • Nuclei react 136 • Bombs and nuclear reactors 137 • Curiosities and challenges on radioactivity 138 • Summary on nuclei 143 144 6 The sun, the stars and the birth of mat ter The Sun 144 • Why do the stars shine? 145 • Why are fusion reactors not common yet? 148 • Where do our atoms come from? 150 • Curiosities about the stars 151 • Summary on stars 152 The strong interaction The feeble side of the strong interaction 153 • Bound motion, the particle zoo and the quark model 154 • The Lagrangian of quantum chromodynamics 156 • Experimental consequences of the quark model 159 • Confinement of quarks – and elefants 161 • Asymptotic freedom 164 • The sizes and masses of quarks 165 • The mass, shape and colour of protons 166 • Curiosities about the strong interactions 167 • A summary of QCD 169 The weak nuclear interaction and the handedness of nature Transformation of elementary particles 171 • The weakness of the weak nuclear interaction 172 • Distinguishing left from right 173 • Distinguishing particles and antiparticles, CP violation 175 • Weak charge, mixings and symmetry breaking 176 • The Lagrangian of the electroweak interaction 178 • Curiosities about the weak interaction 180 • A summary of the electroweak interaction 184 The standard model of elementary particle physics – as seen on television Summary and open questions 189 153 7 Motion Mountain – The Adventure of Physics available free of charge at www.motionmountain.eu 171 8 186 9 191 10 Dreams of unification Grand unification 191 • The data 192 • The state of grand unification 193 • Searching for higher symmetries 194 • Supersymmetry 194 • Dualities – the most incredible symmetries of nature 195 • Collective aspects of quantum field theory 197 • A summary on higher symmetries 198 11 Bacteria, flies and knots Bumblebees and other miniature flying systems 199 • Swimming 203 • Rotation, falling cats and the theory of shape change 206 • Swimming in curved space 209 • Turning a sphere inside out 210 • Clouds 211 • Vortices and the Schrödinger equation 212 • Fluid space-time 215 • Dislocations and solid space-time 216 • Polymers 218 • Knots and links 220 • The hardest open problems that you can tell your grandmother 221 • Curiosities and fun challenges on knots and wobbly entities 223 • Summary on wobbly objects 226 12 Q uantum physics in a nu tshell Achievements in precision 228 • Physical results of quantum theory 230 • Results of quantum field theory 232 • Is quantum theory magic? 234 • The dangers of buying a can of beans 235 • The essence of quantum theory 236 • What is unexplained by quantum theory and general relativity? 236 • How to delude oneself that one has reached the top of Motion Mountain 239 • What awaits us? 242 a Composite particle properties 199 Copyright © Christoph Schiller November 1997–January 2009 228 244 Motion Mountain – The Adventure of Physics available free of charge at www.motionmountain.eu Copyright © Christoph Schiller November 1997–January 2009 contents 259 279 286 14 Credits Film credits 286 • Image credits 286 Challenge hints and solu tions Biblio graphy Chapter 1 MOTION FOR ENJOYING LIFE S ince we now can look at quantum effects without ideological baggage, let us have ome serious fun in the world of quantum theory. The quantum of action has ignificant consequences for medicine, biology, chemistry, material science, and engineering. We will only explore a cross-section of these topics, but it will be worth it. But also art, the colours and materials it uses, the creative process in the artist, are based on quantum physics.** From a physics standpoint, all these domains study small motions of electric charges; thus understanding the details requires quantum theory – though usually not much. Three special forms of electromagnetic motion are of special importance to humans: life, reproduction and death. We mentioned at the start of quantum theory that none of them can be described by classical physics. Life, sexuality and death are quantum effects. Let us see why. “ Homo sum, humani nil a me alienum puto.* Terence ” Motion Mountain – The Adventure of Physics available free of charge at www.motionmountain.eu biolo gical machines Living beings can be described as objects showing metabolism, information processing, information exchange, reproduction and motion. Obviously, all these properties follow from a single one, to which the others are enabling means: ⊳ Living beings are objects able to (self-)reproduce.*** From your biology lessons in secondary school you might remember the main properties of heredity. Reproduction is characterized by random changes from one generation to the next. The statistics of mutations, for example Mendel’s ‘laws’ of heredity, and the lack of intermediate states, are direct consequences of quantum theory. In other words, reproduction and growth are quantum effects. * ‘I am a man and nothing human is alien to me.’ Terence is Publius Terentius Afer (c. 190–159 bce ), the important roman poet. He writes this in his play Heauton Timorumenos, verse 77. ** The photograph on page 11 shows a soap bubble, the motion of the fluid in it, and the interference colours; it was taken and is copyright by Jason Tozer for Creative Review/Sony. *** However, there are examples of objects which reproduce and which nobody would call living. Can you find some examples, together with a sharper definition? Copyright © Christoph Schiller November 1997–January 2009 Challenge 2 s 16 motion for enjoying life In order to reproduce, living beings must be able to move in self-directed ways. An object able to perform self-directed motion is called a machine. All self-reproducing beings are machines. Since reproduction and growth is simpler the smaller the system is, most living beings are extremely small machines for the tasks they perform, especially when compared to human made machines. This is the case even though the design of human machines has considerably fewer requirements: human-built machines do not need to be able to reproduce; as a result, they do not need to be made of a single piece of matter, as all living beings have to. Indeed, despite all the restrictions nature has to live with, living beings hold many miniaturization world records: — The brain has the highest processing power per volume of any calculating device so far. Just look at the size of chess champion Gary Kasparov and the size of the computer against which he played. Or look at the size of any computer that attempts to speak. — The brain has the densest and fastest memory of any device so far. The set of compact discs (CDs) or digital versatile discs (DVDs) that compare with the brain is many thousand times larger. — Motors in living beings are many orders of magnitude smaller than human-built ones. Just think about the muscles in the legs of an ant. — The motion of living beings beats the acceleration of any human-built machine by orders of magnitude. No machine moves like a grasshopper. — Living being’s sensor performance, such as that of the eye or the ear, has been surpassed by human machines only recently. For the nose this feat is still far away. Nevertheless, the sensor sizes developed by evolution – think also about the ears or eyes of a common fly – are still unbeaten. — Living beings that fly, swim or crawl – such as fruit flies, plankton or amoebas – are still thousands of times smaller than anything built by humans. In particular, the navigation systems built by nature are far smaller than anything built by human technology. — Can you spot more examples? The superior miniaturization of living beings – compared to human-built machines – is due to their continuous strife for efficient construction. In the structure of living beings, everything is connected to everything: each part influences many others. Indeed, the four basic processes in life, namely metabolic, mechanical, hormonal and electrical, are intertwined in space and time. For example, breathing helps digestion; head movements pump liquid through the spine; a single hormone influences many chemical processes. In addition, all parts in living systems have more th..."

You need to upgrade your Flash Player , or try to enable javascript in order see this document properly.