And then, in the 1920s, there came along this American
 astronomer by the name of Edwin Hubble of the University of
 Chicago.  Hubble used a technique called "red shifts" (which is
 akin to the Doppler effect in sound), seeing the shifting,
 frequency and amplitude of light waves.  He noticed that red
 shifts indicate that something is receding away from you quite
 quickly, and a blue shift indicates that something is coming
 toward you quite quickly.  At any rate, the main thing to
 remember here is that what Hubble discovered, as he moves out
 further and further into the universe looking through his
 telescope at distant galaxies, is that the red shift is
 increasing.  With this in mind, he was able to calculate (a long
 story) is not only that the universe is indeed expanding, but it
 is slowing down in its expansion.  And he is able to calculate
 very precisely the degree to which the universe is slowing down
 in its expansion.  And insofar as he is able to do it, he knows
 the force that is causing the universe to slow down, that is, the
 universal force of attraction between particles, which is
 gravity.  He also knows the precise amount of gravity in the
 universe that would slow it down to this degree over, say, 18
 billion years.  After calculating this, Hubble goes one step
 further:  he knows that mass, distance and gravity are related. 
 He knows the total amount of gravity in the universe; he
 therefore knows the total amount of mass in the universe.  It so
 happens that he thought the mass of the universe is 10^76 number
 worth of Hydrogen atoms worth of mass.  That's a big number, but
 it is very finite.  It dispelled the entire Newtonian concept of
 infinite space, mass, distance and time in the universe.  And
 Hubble knew that really it couldn't be much more than 10^76
 number of Hydrogen atoms of mass.  He certainly knew it couldn't
 be more than 10^78 number wort of Hydrogen atoms, for if the
 mass was 1,000x greater (10^2), gravity would also be 1000x
 greater.  If gravity was 1000x greater, so would the attraction
 be between particles in the universe.  If this were the case, the
 universe would have collapsed in upon itself six seconds after
 the big bang.  And as we shall see in a moment, that would be the
 end, because it would have collapsed into a Schwarzchild black
 hole never to re-expand again.  In short, what Hubble discovered
 was a most amazing fact:  not only is the mass of the universe
 finite, but this finite amount of mass is only propagated through
 the finite volume of the universe for a finite amount of time. 
 He speculated approximately 18 billion years, which is a figure
 we pretty much still hold onto today.  
  
      But other kinds of really spectacular discoveries happened
 in the wake of Hubble's discovery.  For what Hubble knew was that
 if the universe were to get an initial momentum that large, to be
 able to spread out to 10^76 number of hydrogen atoms of light,
 over an 18 billion light year diameter, there must have been an
 incredible force or explosion at the very beginning (i.e. the
 "big bang.")  Now Hubble knew that there would be a residual
 force left over from such a bang because, after all, any time
 when there is a real explosion, there is a residual shockwave. 
 And this shockwave would leave its own sign; a sign which would
 prove that the only place this radiation could have ever arisen
 is at the very beginning of the universe itself.  In short, if
 there was a completely uniformly distributed radiation throughout
 the universe, where there was very little frequency difference,
 the only way that could have happened is if the explosion was
 concurrent with the actual creation of the space-time continuum
 itself.  This, in General Relativity theory is called a
 singularity.  That is to say, the entire universe collapsed into
 a dimensionless point.  If the explosion happened before the
 space-time continuum was present, when the universe was a
 dimensionless point -- then and only then could that explosion --
 that residual radiation shockwave left over from the explosion
 spread out across the entire universe in a uniform distribution. 
 In 1964 it was discovered by two physicists in Bell laboratories,
 and in 1968 Penzias and Wilson, who discovered it, were awarded
 the Nobel prize for discovering the Big Bang.
  
 (continued next post)