《超弦与一些别的事情》（英文版）Calle Superstrings and other things，A GUIDE TO PHYSICS

SUPERSTRINGS AND OTHER THINGS A GUIDE TO PHYSICS CARLOS I CALLE NASA Kennedy space center loP Institute of Physics Publishing Bristol and Philadelphia



    
  

 /
  //
     !   & 0  

CONTENTS PREFACE PaRt 1: INTRODUCTORY CONCEPTS 1 PHYSICS: THE FUNDAMENTAL SCIENCE 3 What is physics? The scientific method: learning from our mistakes Physics and other sciences Sizes of things: measuremen Fundamental units Physics and mathematics 3589 Frontiers of physics: Very small numbers Pioneers of physics: Measuring the circumference of the Earth PaRT 2: THE LAWS OF MECHANICS THE DESCRIPTION OF MOTION Understanding motion Uniform motion 55% The frontiers of physics: Friction Instantaneous speed Velocity: Speed and direction Vectors Acceleration 901145 Uniformly accelerated motion Falling bodies The motion of projectiles


  .   +
     
 3 

8   . * /
 7 <   @ 7  - "8 & !"  "' 5      =
? ! &8 "" 37 ."  36    "" 3A      !  ! 3=    "   !   #   12
      1    
        . *      16 & " 16 !" " 1; &  15 $       1=   72 4 8
   73 4 73  7B !"  " 76 .&  75    % & !  7=  " ! , B2 

SUPERSTRINGS AND OTHER THINGS 3 THE LAWS OF MECHANICS NEWTON'S LAWS OF MOTION The concept of force The ancient idea of motion The birth of modern science Pioneers of physics: Galileo's dialog with aristotle Galileo formulates the law of Inertia Physics in our world: The Leaning Tower of pisa Newton's First Law: Law of inertia Physics in our world: Car seat belt ewton's Second Law: Law of force Newton's Third Law: Law of action and reaction 4 ENERGY What is energy? The concept of work 3457802569222667 Units of work and energy The concept of energy Pioneers of Physics: James Prescott Joule(1818-1889) The work-energy theorem Conservative and nonconservative forces 5 CONSERVATION OF ENERGY AND MOMENTUM Transformation of energy The principle of conservation of energy The energy of mass Efficiency pioneers of physics: The phnysicists'letters Power Physics in our world: Automobile efficiency Impulse and momentum Physics in our world: Air bags Conservation of momentum 888888888999 Elastic and inelastic collisions Cannons and rockets 6 ROTATION AND THE UNIVERSAL LAW OF GRAVITATION Rotational motion The frontiers of physics: CD-ROM drives 91m Torque and angular momentum

7   / <
. * 
8   <    C
/ <
 . *      B7   ! ! B7    ! " BB   ! "  B6    % &   '     B5  !"  /% !  BA    ' $   $'   62 %C . /%8 /% !  61    '     6B %C
 /%8 /% ! ! 6; %C  /%8 /% !    6= B      ;1 <  & @ ;1   ! %' ;1  ! %'  & ;;   ! & ;;    ( !  ( )*+*+,*++-. ;5  %'(& " 5B    ! 56 6 
4  .    *  *    * 5A !" ! & 5A   !  ! & A2  & ! " A3 !- A1    $  &   A7 % A6    '  ! / A; "  """ AA    '    =2  ! """ =3     =B   ' =6 ;      4
/ / <  .  4       =A  " =A $     01"  323 :  & """ 321


    


Physics in our world: Twisting cats Satellites Origins of our view of the universe 110 Keplers laws of planetary motion 114 Newton,s law of universal gravitation The frontiers of physics: Measuring the distance to the Moon Spacecraft and orbital motion The frontiers of physics: The Global Positioning Satellite System 128 part 3: THE STRUCTURE OF MATTER Z ATOMS: BUILDING BLOCKS OF THE UNIVERSE The underlying structure of matter The Atomic Hypothesis concept of the ator irst models of the atom 346 Waves and quanta The bohr model of the atom 145 Molecules 147 Physics in our world: Winemaking 8 THE HEART OF THE ATOM THE NUCLEUS Raw material: Protons and neutrons Pioneers of physics: Heisenbergs failing grade The composition of the nucleus 153 The glue that keeps the nucleus together Size and shape of the nucleus Nuclear energy levels 9 FLUIDS 164 states of matter Buoyancy Surface tension and capillarity Fluids in motion The human cardiovascular system 6669868 Physics in our world: Curve balls

   ' $'    32;   32A
 332 & !  % !   332 $C % !  " 33B %C % !  & 33A $     "       " 31B
!   " 316 $     $ %       ! 31A
      5 *
8 0/ 0/$
.     4  
 377   &  ! " 377  "  377   !  " 37B . " !  " 37; <  : 3B3  0 " !  " 3B6 * 3B5    ' 2! 3 3B= A     .   *8     / 
363 % "8    363    4&     361  " !   367  &  '   & 366
?   !   36=  &  3;3 = . /  
3;B
 ! " 3;B  3;6  3;; 0  35;
!    35= .  " 3AB  "   " 3A;    '    3A5  +

SUPERSTRINGS AND OTHER THINGS PaRt 4: THERMODYNAMICS 10 HEAT AND TEMPERATURE Heat as a form of energy Pioneers of physics: Count Rumford Measuring temperature Temperature and heat Physics in our world: Thermography eat Heat of fusion and heat of vaporization Evaporation and boiling Physics in our world: Instant ice cream Humidity Thermal expansion 215 The unusual expansion of water 11 THE LAWS OF THERMODYNAMICS The four laws of thermodynamics The ideal gas law 221 Physics in our world: Automobile engines The zeroth law of thermodynamics The first law of thermodynamics The second law of thermodynamics The third law of thermodynamics The frontiers of physics: Entropy that organizes? Entropy and the origin of the Universe Entropy and the arrow of time Part 5: ELECTRICITY AND MAGNETISM 12 ELECTRICITY Electromagnetism Electric charge Coulombs law The electric field The fundamental charge The frontiers of physics: Electrostatics on Mars Electric potential he frontiers of physics: Storing single electrons Physics in our world: Inkjet pr

    32       *      3=6    !" ! & 3=6     0! 3=5 *& " 3== "   123    ' $!  12B   126  ! !   ! ? 125   & 132    ' 5    ! 137 " 137 " + 136   + ! % 13A 33   / <
 .    *     *  
113  ! % ! " " 113   & % 113    '  !  11B  ? % ! " " 116  - % ! " " 11;   % ! " " 11=   % ! " " 177 $     #     67 17B    & !   176    % ! " 17=
     31  /          1B5 "&" 1B5  & 1BA "C % 162   - 167  !" & 16; $     #    "  16A   1;2
&  & 1;1 $         1;B    ' 538   1;6


    
+

13 APPLIED ELECTRICITY Conductors and insulators Electric current and batteries Physics in our world: Electric cars 271 The frontiers of physics: Electric dentists Simple electric circuits Resistor combinations Electrical energy and power emiconductors 14 ELECTROMAGNETISM The discovery of magnets The magnetic field Physics in our world: Magneto-optical drives Electric currents and magnetism moving charge in a magnetic field Particle accelerators Magnetism of the earth Physics in our world: Avian magnetic navigatio The source of magnetism Faradays law of induction Motors and generators Maxwells equations Physics in our world: Microwave ovens PART 6: WAVES 15 WAVE MOTION The nature of waves The principle perposition Resonance and chaos The frontiers of physics: Chaos in the brain 337 16 SOUND The speed of sound 343 Physics in our world: Telephone tones Intensity of sound waves

37 /     /          1;5    1;5     1;A "C /% 152    ' #    153 $     #     156
"   156  " 15A  &  % 1A2
" 1A3
 1A5 3B  /      *    
* 1=3   ! "& 1=3  "& - 1=1    ' "      1=6    "&" 1=6 "& &   "& - 1=A   723 *&" !   72B    '   !      725   ! "&" 725 . C % !  72= *  & 731 *+%C : 736    ' "'   735
   36 < 4  *      713   ! % 713   !  716    777 $           77; < % 775
" % 77= 3;
   7B1   !  7B1   !  7B7    ' $   7BB  !  % 7B;  +

SUPERSTRINGS AND OTHER THINGS The sound of music Musical instruments The Shockwaves Ultrasound 17 OPTICS 370 Reflection of light Reflection from mirror Curved mirrors Refraction of light The frontiers of physics: Gradient-index lenses Total internal reflection Optical instruments The human eye The frontiers of physics: Artificial vision 1 8 THE NATURE OF LIGHT The The speed of light The electromagnetic spectrum Color 417 421 Polarization 425 Physics in our world: Compact disc player 435 PaRT 7: MODERN PHYSICS 19 THE SPECIAL THEORY OF RELATIVITY 441 Galilean relati The Michelson-Morley experiment Einsteins postulates Time dilation The frontiers of physics: Intergalactic travel Length contraction

  7B5 $     #    !    761   ! " 761 * " 765   !! 7;1
'% 7;6  7;5 35    
752 < ! & 752 D ! & 752 D !" " 75B  " 75; ! ! & 7A2 $     %  9  7A=   D 7=2  " 7=7  "   7== $      /   B27 3A        . /   B26  %  ! & B26   ! & B2;  "& " B33  B37
8  & ! " B35 &C +" B13 ? B16 / B72    ' !     B7B & B76
   
  3=  
   /       .   /   4    BB3   BB3  *E* +" BB6 C  BB= "  B67 $     5       B6A
" B;2 /&  B;1


    
+

Addition of velocities 20 THE GENERAL THEORY OF RELATIVITY 469 The principle of equivalence The bending of light The perihelion of Mercury The gravitational time dilation The frontiers of physics: Orbiting clocks The frontiers of physics: Spacetime drag 94 21 THE EARLY ATOMIC THEORY The physics of the atom Black body radiation The photoelectric effect The bohr model of the atom revisited Physics in our world: Using photons to detect tumors De broglie waves antum mechanics 22 QUANTUM MECHANICS The beginnings of quantum mechanics 511 The new mechanics of the atom 51 Wave mechanics Pioneers of physics: Schradinger's inspired &u Heisenbergs uncertainty principle The new physics The frontiers of physics: Knowledge and certainty Physics in our world: Electron microscopes The frontiers of physics: Quantum teleportation 23 NUCLEAR PHYSICS 532 Bevond the atom Radioactivity Nuclear reactions Nuclear energy: Fission and fusion Applications of nuclear physics Pioneers of physics: Enrico Fermi (1901-1954 Physics in our world: Proton beams for cancer therapy

 !  B;B # !1 B;6 12       /       .   /   4    B;=   ! : B;= ?. 6B5    '    !      661  +

SUPERSTRINGS AND OTHER THINGS 24 ELEMENTARY PARTICLES Antimatter The fundamental forces 555 Exchange forces Particle classification: Hadrons and leptons Strange particles Quark Pioneers of physics: Gell-Mann's quark Particles with charm 25 SUPERFORCE: EINSTEIN'S DREAM 571 Global and local symmetries The electroweak unification The color force GUTs. the third unification The creation of the universe The first moments of the universe The frontiers of physics: The cosmic background explorer 594 Appendix A POWERS OF TEN Appendix B THE ELEMENTS AppendixC NOBEL PRIZE WINNERS IN PHYSICS Appendix D PHYSICS TIME-LINE Glo Inde XIV

1B  /  *          / 
667 " 667  !" ! 666 +& ! 665  66=  -8    6;3  % 6;7
&  6;6 F' 6;6    %" & @ 3 6;A  % " 6;A 16
  .     8   
    C
   * 653
"" 653     "" 657  %' - 656   ! 6A3 )   - 6AB
 ""  & 6A6   !   6AA  - "" !   6=3 $     $ !  3 9  6=B +  <  
 .    6=; + 0    /  *   
6== +    0  /   G  <     
  
 
;21 +  
 
  *  ( /    ;2A  ;36 + ;71


    
+

PREFACE As a research scientist at NASA Kennedy Space Center working on planetary exploration, I am very fortunate to be able to experi ence first hand the excitement of discovery. As a physicist, it is not surprising that I find science in general and physics in particular captivating. I have written this book to try to convey my excite- ment and fascination with physics to those who are curious about nature and who would like to get a feeling for the thrills that scientists experience at the moment of discovery The advances in physics that have taken place during the twentieth century have been astounding. One hundred years ago, Max Planck and Albert Einstein introduced the concept of the quantum of energy that made possible the development of quantum mecha panics. This revolutionary theory opened the doors for the breathtaking pace of innovation and discovery that we have witnessed during the last fifty years At the beginning of the new century, physics continues its inexorable pace toward new discoveries. An exciting new theory might give us the"theory of everything, the unification of all the forces of nature into one single force which would reveal to us how the universe began and perhaps how it will end Although these exciting new theories are highly mathemati cal, their conceptual foundations are not difficult to understand As a college professor for many years, I had the occasion to teach physics to nonscience students and to give public lectures on physics topics. In those lectures and presentations, I kept the mathematics to a minimum and concentrated on the concepts The idea for this book grew out of those experiences This book is intended for the informed reader who is inter- ested in learning about physics. It is also useful to scientists in other disciplines and to professionals in non-scientific fields The book takes the reader from the basic introductory concepts

.       
$
  %'&   +)  "  !     +(  -   +" !  #    )    &   -   &      &#   %  '     " +( "  ! %     %      % % '  &  !& !     +   "" !  #        '  &  %    &#    &) *+ '       !  :" ! &  "   " ! :" "#       !  '&  !     %  % &   -! #   && !  %  )     +  % % #  +& %  "& &   HH !  &)CC  - !   ! !    & ! % %    %   &   %  % # &  +& %   & ""( )   !   !-  #   & ! ! " )              &      #     )  '  ""   """     #   !  ' &%  !  +#  '   !  !"  %  (   &   #    !        !  (- -#  ' '   !"     +