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Wednesday, August 13, 2008

The Law of Falling Objects....

What Is It?
Ob jects fall at the same speed re gardless of their weight. Who Dis cov ered It? Ga li leo Galilei

Year of Dis cov ery: 1598

Why Is This One of the 100 Great est?

It seems a sim ple and ob vi ous discov ery. Heavier ob jects don’t fall faster. Why does it qualify as one of the great dis cov er ies? Be cause it ended the prac tice of sci ence based on the an cient Greek theo ries of Ar is totle and Ptolemy and launched mod ern sci ence. Ga li leo’s dis cov ery brought phys ics into the Re naissance and the mod ern age. It laid the foun da tion for New ton’s dis cov er ies of uni ver sal grav i ta tion and his laws of mo tion. Ga li leo’s work was an essen tial build ing block of modern physics and engineering.

How Was It Dis cov ered?

Ga li leo Galilei, a 24-year-old math e mat ics pro fes sor at the Uni ver sity of Pisa, It aly, of ten sat in a lo cal ca the dral when some nag ging prob lem weighed on his mind. Lamps gently swung on long chains to il lu mi nate the ca the dral. One day in the sum mer of 1598, Ga li leo re al ized that those lamps al ways swung at the same speed.
He decided to time them. He used the pulse in his neck to measure the period of each swing of one of the lamps. Then he timed a larger lamp and found that it swung at the same rate. He borrowed one of the long ta pers al ter boys used to light the lamps and swung both large and small lamps more vig or ously. Over many days he timed the lamps and found that they al ways took ex actly the same amount of time to travel through one com plete arc. It didn’t mat ter how big (heavy) the lamp was or how big the arc was.
Heavy lamps fell through their arc at the same rate as lighter lamps. Ga li leo was fas ci ¬nated. This ob serva tion con tra dicted a 2,000-year-old cor ner stone of be liefs about the world.
He stood be fore his class at the Uni ver sity of Pisa, It aly, hold ing bricks as if weigh ing and compar ing them—a sin gle brick in one hand and two bricks that he had ce mented to ¬gether in the other. “Gen tle men, I have been watch ing pen du lums swing back and forth. And I have come to a con clu sion. Ar is totle is wrong.”

10 The Law of Fall ing Objects

The class gasped, “Ar is totle? Wrong?!” The first fact ev ery school boy learned in be¬gin ning sci ence was that the writ ings of the an cient Greek phi los o pher, Ar is totle, were the foun da tion of sci ence. One of Ar is totle’s cen tral the o rems stated that heavier ob jects fall faster be cause they weigh more.
Ga li leo climbed onto his desk, held the bricks at eye level, and let them fall. Thud! Both bricks crashed to the floor. “Did the heavier brick fall faster?” he de manded.
The class shook their heads. No, it had not. They landed to gether.
“Again!” cried Ga li leo. His stu dents were trans fixed as Gali leo again dropped the bricks. Crash! “Did the heavy brick fall faster?” No, again the bricks landed to gether. “Ar is ¬totle is wrong,” de clared their teacher to a stunned cir cle of students.
But the world was re luc tant to hear Ga li leo’s truth. On seeing Gali leo’s brick dem on ¬stra tion, friend and fel low math e ma ti cian Ostilio Ricci ad mit ted only that “This dou ble brick falls at the same rate as this sin gle brick. Still, I can not so eas ily be lieve Ar is totle is wholly wrong. Search for another explanation.”
Ga li leo decided that he needed a more dramatic, ir re fut able, and pub lic dem on stration. It is be lieved (though not sub stan ti ated) that, for this demon stration, Gali leo dropped a ten-pound and a one-pound can non ball 191 feet from the top of the famed Lean ing Tower of Pisa. Whether he ac tu ally dropped the can non balls or not, the science discovery had been made.

Fun Facts:

Speak ing of fall ing ob jects, the high est speed ever reached by a woman in a speed skydiving com pe ti tion is 432.12 kph (268.5 mph). Italian dare devil Lu cia Bottari achieved this re cord-break ing ve loc ity above Bottens, Switzerland, on Sep tember 16, 2002, dur ing the an nual Speed Skydiving World Cup.


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