Breaking Away:
     PEOPLE IN GLASS HOUSES SHOULD NOT THROW STONES.  THE STONE WON'T BREAK,
BUT THE GLASS CERTAINLY WILL.  THIS IS PRETTY INTUITIVE,  BUT SCIENTISTS HAVE HAD HARD
TIME FIGURING OUT JUST WHY CERTAIN THINGS BREAK AND OTHERS DON'T.  ON A
MOLECULAR LEVEL, IT'S TOUGH TO FIGURE OUT WHAT'S SO DIFFERENT BETWEEN A ROCK
AND A SHEET OF GLASS. 

     Marder: "If you look at how individual atoms pull on each other they're . . . very
strong and they pull very very hrad and if you try to do calculations based on that you
find that you'd have to pull on things 10, 100 times harder than any child knows you really
do." 

     MICHAEL MARDER IS A PHYSICIST AT THE UNIVERSITY OF TEXAS.  HE SAYS THAT
FIGURING OUT WHY THE CALCULATIONS ARE SO FAR OFF HAS TAKEN US THE BETTER PART
OF THIS CENTURY.  PAR T OF THE PROBLEM IS THAT YOU CAN'T REALLY UNDERSTAND THE
BREAK WHEN YOU LOOK AT ONLY A FEW ATOMS. 

     Marder: "A crack is a pretty big thing, a lot of atoms take part in it they all work
together, they cooperate. . . until you look at something large enoguh and complicated
enough to have a crack going through it you have no hope of getting anything
particularly right."

     MARDER IS ONE Of THE PEOPLE WHO'S BEEN LOOKING AT CRACKS FROM A
LARGER SCALE.  HE'S FOUND THAT GLASS MOLECULES PRACTICALLY UNZIP--CREATING AN
EASY BREAK, WHILE SOMETHING LIKE A ROCK DISPERSES THE FORCE  INTO A MAZE OF TINY
BREAKS.

     Marder:  "If you get a crack started in glass that crack really moves.  and its very
hard to stop. . .if you start a crack in brick it turns this way , it turns that way, it gets
bumped, it gets jiggled, the crack splits into two, the crack splits into four, the crack
stops."

     THE KEY IS THE WAY THAT THE ATOMS ARE LINED UP--SOME MATERIALS PREPARE A
NICE SMOOTH TRACK FOR THE CRACK, WHILE OTHERS CREATE AN OBSTACLE COURSE. 
WHILE WE MAY HAVE LEARNED MORE ABOUT WHY THINGS BREAK, MARDER SAYS THE TAKE
HOME MESSAGE IS STILL THE SAME: BUILD YOUR HOUSE OUT OF BRICK NOT GLASS.