[at lighthouse,  Pigeon  Point, California We've seen, by looking
 at nature on the subatomic scale, that the structures of matter and
 energy, and even the nature of the fundamental forces thought to govern
 their behavior  throughout the universe, would have been simpler under
conditions of extremely high energy.

   And we've  seen by looking at nature on the large scale--out in the
 expanding universe of galaxies--that the universe began in just such a
 state of high energy.   By putting these two lines of inquiry together,
 scientists  have been able to trace the broad outlines of cosmic history
 from the first fraction of a second of the Big Bang down to  the present
 day.

    We don't know all the details of this story by any means, of course.
 Parts of it are missing; much of what's been surmised is doubtless
 distorted or simply wrong. But even at this early stage it's possible
 to discern the grandeur and beauty, and the extraordinary explanatory
 power of what is,  after all, the ultimate history  story--the history
 of the universe,  the story of how a single kernel  of energy could have
become everything that there is.

   To examine the scientific  account of genesis and evolution in detail,
 suppose that  the steps leading up to  the tower of this old lighthouse
 could carry us backward  into  cosmic  history,  so  we could  scrutinize
 every thread  in  the long tapestry of time.

    [enters  lighthouse]   Let's  imagine that  each of the windows in the
 lighthouse looked out on an earlier epoch in cosmic history, so that this
 first window  let us  see the  way  the  universe looked  when  it was
 only one billion years old. And that each step up the stairway from there
 on  took us  back to when the universe was one tenth its previous
 age--to only  100  million  years after the Big Bang, then 10 million,
 one billion, and so forth.

 Walking in this way, we very  soon would have reached the first  second
 of time.  And that's important, because a lot happened during that first
 second.

 Our  galaxy--and pretty much  all the other galaxies,  so far as we can
 tell--formed during the first billion years of the expansion of the
 universe, when the primordial gas was still thick enough to congeal
 readily into stars and galaxies.  We don't know all the specifics of how
 the galaxies formed, by any means, but we think we have a pretty good
 picture of what the young Milky Way might have looked like.  And here it
 is.  [opens window, exposing computer animation of the Milky  Way
 protogalaxy--a spiral blazing with brilliant young stars, enshrouded in
 primordial dust and glowing red gas]  These first generation stars were
 composed almost entirely of hydrogen and helium. If there was any
 intelligent life in the early days of the universe, the periodic table
 up at the  front of the high school chemistry class would have had just
 two squares in it--hydrogen and helium.

 [climbing stairs; opening next window reveal computer animation of photon
 decoupling]  Once the universe had been expanding for about one million
 years, it had thinned out enough so that photons could fly freely through
 space without constantly running into other particles. The result was the
 dawn of light. This was also the date of the birth of the first atoms.
 Free at last from harassment by the photons, electrons could settle down
 in orbit around atomic nuclei. One electron orbiting one proton gives you
 an atom of hydrogen, the simplest and most abundant of all the elements.
 Two electrons orbiting a pair of protons, plus a couple of neutrons, gives
 you a tidy little atom of helium. But those helium nuclei were already on
 hand.   They must have formed at an even earlier epoch.

 (up to the next window)  The creation of helium nuclei dates from when
 the universe was about one hundred seconds old. That's the first point at
 which things had cooled off enough so that protons and neutrons could get
 together and form nuclei of atoms, without constantly being torn asunder
 again in the all pervasive heat.  [opens window onto helium synthesis
 animation]  Now, for the first time,  protons and neutrons are able to
 cling together-thanks to the strong force.  They tend to form triplets,
 and the triplets combine to make an unstable nucleus. Two of the extra
 protons are thrown off, and the result is a stable nucleus of helium.

    This elaborate mating ritual seems to have been pretty popular in the
 early days, so popular that the theorists calculate that about one quarter
 of all the stuff in the universe should have congealed into helium gas.
 And sure enough, when astronomers study the chemical composition of the
 universe at large today, they find that it's about one quarter helium.
 It's this sort of confirmation of theory by experiment that leads
 scientists to think that they really do understand something of how
 helium atoms formed in the fires of the Big Bang.

   [up the stairs]  We're climbing now into very early times.  When the
 universe was one second old, the heat was so intense that it overwhelmed
 even the strong nuclear force.  That's the force that holds quarks
 together to make protons and neutrons.  From here on up, even such
fundamental structures as protons and neutrons can't exist, and the
 universe is a soup of free quarks.  A tenth of a second...one hundredth
 of a second after the beginning of time.  The universe now is so dense
 that even neutrinos, subatomic  particles  so  aloof that they can
 normally fly through a trillion-mile block of solid lead without hitting
anything--even neutrinos are now bound up in the universal broth of matter
and energy.

   (opens fourth window: electroweak interactions]  One 10 billionth of
 a second after the beginning, the heat was sufficiently intense that the
 electromagnetic and weak forces were still welded together and functioned
 as a single unified force, the electroweak force.  Z particles could be
 created in abundance out of the heat of the electroweak epoch. Weak bosons
 and photons acted interchangeably, and the universe was ruled, not by four
 forces, but by three.

 continued...

--- FMail 1.22