TIMOTHY FERRIS:   The baseball  and  the bat are mostly empty space.
 Their solidity is an illusion  created by the electromagnetic  force
 field that binds their atoms together.

   [video:   computer animation of photons being generated as the bat
 and ball approach each other]  Viewed on the subatomic level, a home
 run begins with the exchange of photons between atoms in the bat and
 the atoms in the ball.   The ball is repelled  and flies  away.   We
 credit  the  home  run  to  the  batter,  but the fundamental  force
 responsible   is   electromagnetism.     Infinite  in   range,  it's
 electromagnetism  that  carries  us  light  from  the sun and stars.
 The weak nuclear  force  helps power the sun, and presides over  the
 phenomenon  of  nuclear   decay.  Tremendous amounts  of energy  are
 bound up  in the nucleus of each atom.   Some  nuclei  are unstable,
 and can't  contain  their energy forever.  When they decay, it's the
 weak  force,  carried by particles  called weak bosons, that governs
 the process.

   The strong nuclear force binds quarks together to make protons and
 neutrons.   Without it,  there would be no atoms,  and the  universe
 would be a quark fog.  The strong force is carried by particles that
 the  physicists call gluons,  because they act like the most perfect
 imaginable glue.
   [video:   computer  animation of baseball flying across a  gravity
 grid] Gravitation, the universal attraction of all massive particles
 toward one another, is the weakest of  the four forces.  But gravity
 has infinite  range,  and  it always  attracts,  never  repels. This
 single-minded   dedication  makes gravity the  force that holds  the
 planets, the stars and galaxies together.

   But why  are there  four forces [electromagnetism;  weak;  strong;
 gravity], and why  do they  differ so profoundly in character?

    [video:   footage and stills of Einstein  at Princeton]  Einstein
 tried in vain to find an answer to that question.  He sought what he
 called,  "a  simple  and  lucid  image  of  the  world,"   a  single
 principle  that would account  for  the baffling differences between
 the  forces  and  the  great  variety  of  particles.  "What  really
 interests  me,"  he  said,  "is whether  God had  any choice in  the
 creation of the universe."

   He failed in that effort,  but he never lost his faith that, as he
 put it,  "God  is subtle,  but not malicious,"  that nature,  though
 difficult  to  understand,  ought  at  the  root  to  be  simple and
 beautiful.

   [Ferris  in   Einstein's  old  office,  standing in  front of  the
 blackboard] Albert Einstein spent the last years of his life in this
 office at the Institute for Advanced Study in Princeton,  New Jersey,
 working on the search for a unified  theory of the forces of nature.
 He never found it,  and  the  equations  remained  unfinished on the
 blackboard on the day he died.

   Today,  the equations  look a  lot different, and they go by fancy
 names  that   Einstein   never  heard  of,   like  supergravity  and
 supersymmetry, and superstring theory.  But their  goal is the same:
 to draw the disparate elements of physics together into  one  whole.
 Physics today is a patchwork.   There  are theories that account for
 each of the  fundamental  forces,  and they do so  marvelously well.
 They  can predict the behavior of an electron spiraling away from an
 exploding  galaxy,  or the  behavior of these  photons arriving here
 from the sun.

   But they have little  to say about why the forces of nature differ
 so curiously in character. Why, for instance,is there a positive and
 negative electrical charge, but no such thing, so far as we know, as
 negative gravity?   Why do  the strong and weak forces function only
 within the nucleus of the atom,when electromagnetism and gravitation
 are infinite in range?

                                  *****

   [video:    tower   with   ascending   illustrations   representing
 milestones  in the  history of particle physics; at its base,  Plato
 and Aristotle contemplate a bust of Democritus]


   The search for simplicity--the hope of identifying the fundamental
 force, or a basic building block of matter-runs all through the his-
 tory of physics since the days of the ancient Creeks.

  Atomic theory was already an old idea when Plato debated its merits
 with his pupil,  Aristotle.  [5th century  B.C.]  Aristotle proposed
 that there were two basic forces. He called them levity,the tendency
 of light objects to rise, and gravity, the tendency of heavy objects
 to fall.
  The Roman poet Lucretius popularized atomic theory.
                                 *****

 LUCRETIUS:    (Rome, 1st century  B.C.; actor's voice over video  of
 drawing of Lucretius] Beautiful is the world created  by the  atoms.

   A wedding ring wears thin with the passage of years, yet  we never
 see flecks of gold departing from the  ring, for the gold is made of
 tiny atoms.

 TIMOTHY FERRIS:[as video moves upward on the tower] Amid the spirit-
 ualism  of the  Dark Ages, atomic theory, regarded as materialistic,
 was forgotten,  only  to be revived in the age of Isaac Newton,  who
 saw the world as composed of atoms run by the force of gravity.

 NEWTON:    [actor's voice]   The universe is like a perfect machine.
 It is  the  force of gravity  which  holds the  moon and planets  in
 their orbits.

 TIMOTHY FERRIS:   In  the  centuries that followed,  experiments  by
 Robert Boyles, John Dalton and others revealed that, as Ernest Ruther-
 ford put it, the atom  is a complex aggregate, not a  simple entity.
 Rutherford  found  positively   charged  particles--protons--in  the
 nucleus of the atom, and James Chadwick found neutrally charged neu-
 trons there.

  Fresh light was shed on the concept of electrical charge when James
 Clerk Maxwell,  in the  first  modern  unified  theory,  showed that
 electricity  is but an aspect of electromagnetic force.

   For  a  time  it  seemed  that there might be just two fundamental
 forces--electromagnetism and gravitation. But then the force picture
 became more complex when Hideki Yukawa and Enrico  Fermi  and others
 identified  two   previously  undetected forces  acting  within  the
 nucleus--the strong and weak nuclear forces.

 continued...



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