RUSH COUNTY – This week, since I don’t have a lot else to do, I’m going to share a fascinating story with you. Have you ever stopped to wonder why when you throw a ball up in the air it always comes back down? It absolutely never keeps going up! Ah! Gravity, you say? But what is gravity and what is it about gravity that makes objects fall to earth?
Gravity is a phenomenon we ordinarily take for granted, but there’s more to the force of gravity that keeps all of us and most other things, for that matter, on the ground!
About 300 B.C. Aristotle, the Greek philosopher and mathematician, during what has been called the Classical period in Ancient Greece, wrote that heavy objects fall to earth faster than light object. That notion, obviously, seems to make sense. If you drop a rock and a feather both at the same time, it’s fairly certain that the rock will hit the ground before the feather!
As it turns out, Aristotle was completely wrong, which seems to defy all logic!! Some two thousand years later, Galileo, the Italian astronomer, physicist, engineer, and mathematician proved that heavy objects and lighter ones fall at precisely the same speed. Galileo’s full name, just for the sake of curiosity, was Galileo di Vincenzo Bonaulti de Galilei – which is quite a mouthful.
At first blush, who would you believe, Aristotle or Galileo? Do heavy objects fall faster than light ones or do, regardless of their weight, or do they fall at the same speed? Ordinary common sense would suggest that dropping a cannon ball and a feather at precisely the same instant, that both will fall at different speeds. The cannon ball falls to earth instantly while the feather will drift slowly to the ground. What’s different about how fast the cannon ball and the feather fall to the ground? Wind resistance! Who knew? Well, it turns out that the fellow named Galileo knew, way back about around 1589 or 1592. The feather drifts down because, he said, air pressure on the feather from all sides affects the force of gravity, which makes it drift toward earth in the first place! Gravity still pulls the feather down toward the earth regardless of its weight.
Galileo was able to prove Aristotle wrong, they say, by dropping two objects of different weights, such as two different cannon balls from the top of the famous Leaning Tower of Pisa in Pisa, Italy. Remarkably, both objects fell at exactly the same speed despite their different weights. Common sense, even today, would make anyone think that the heavier object would fall faster than the lighter one, but it doesn’t.
To prove that the feather and the cannon ball drop at the same rate, all that’s needed is an everyday vacuum chamber which is a container from which all the air has been removed. But there was an easier way to prove it. Way back in 1971 Apollo 15 astronaut David Scott performed this experiment while standing on the moon, which exists in the vacuum of space where there is no air to cause wind resistance. The fact that there is no air in the vacuum of space is demonstrated by the necessity of space suits the astronauts wore so they could breathe while they were on the lunar surface. Nevertheless, Scott dropped a falcon feather and a hammer from the same height while standing on the moon and, low and behold, they both fell at exactly the same speed and hit the surface at exactly the same instant! The experiment is on film and can be found by Googling it.
Galileo’s experiment, supposedly from the top of the Leaning Tower of Pisa, incidentally, was critical to the development of Sir Issac Newton’s theory of gravity.
Newton was an English mathematician and physicist who lived from 1642-1727. Everyone remembers the legend that Newton was sitting under an apple tree when an apple fell from the tree and hit Newton on the head, which made him wonder why the apple fell from to the ground in the first place. In the 1680s Newton published his “Theory of Universal Gravitation.” The basic idea was that gravity was a force that acts on all matter in the universe. The theory says that an object is attracted to the earth because the earth has a greater mass than Newton’s apple; hence the apple is drawn toward the earth. Since the earth such a huge mass compared to, let’s say, a person, explains why all of us aren’t floating around on the wind right now!
But getting back to Galileo, the British Broadcasting Company did a special on his 16th century experiment here on earth. There’s a huge NASA power facility vacuum chamber near, of all places, Columbus, Ohio, that has the capability of pumping 30 tons of air from this huge chamber from which a cannon ball and a feather were simultaneously dropped. Guess what? They both hit the ground at the same instant, just as on the moon! Newton’s law of universal gravitation, simply put, says any two bodies are attracted to each other, therefore, the pulling force of the earth, called gravity, gives weight to cannon balls, feathers, and apples which makes them fall, or be drawn, to the earth at the same speed in a vacuum.
So, it’s the pull of one object toward another, that’s what keeps the ball coming back down when it’s thrown as high as possible. That’s also why it takes gigantic rockets to get outside the pull of the mass of the earth to do things like put satellites in orbit. And to think, it only took mankind 800 years or so to figure out why things fall down instead of up!
That’s —30— for this week.