October 26, 2020

#08-001: Newton and the Apple

Sir Isaac Newton

Note: With this lesson we'll begin discussing stories from science, literature, art, music, history, philosophy--almost every field of human endeavor and experience, even folk tales. We'll start by examining a well-known story from science. 

Get Ready: What do you know about Sir Isaac Newton? Do you know any stories about him?

It's commonly said that one day, the English scientist Sir Isaac Newton was sitting under an apple tree when a piece of fruit fell and bonked him on the head. Inspired by this, he invented gravity.

But is this story true?

Well, first, gravity cannot have been "invented" by anyone, since it is a property of physical things and inheres in matter. Newton called it "an attractive force."

Well, then, perhaps it was "discovered"? No. People have known from time immemorial that if you step off a cliff, you will fall. The old saying is, "What goes up, must come down"!

Instead, Newton saw an apple fall (it did not hit him on the head!), and asked himself, Why does an apple always fall straight down--perpendicular to the ground--and never left or right or upward, unless acted on by another force, like wind--or someone hitting it with a stick?

Something, he thought, was pulling the apple toward the very center of the earth! His exploration of this phenomenon led him to formulate what is now called "Newton's Law of Universal Gravitation." More important to his studies than an apple was the behavior of the moon, which by logic--since it is traveling at a great speed--ought to fly off into space. What is keeping it from doing so? The attraction between it and the earth--that is, gravity.

His law is best expressed as a complex mathematical formula, but let's try to put it into words:

"Every particle attracts every other particle in the universe with a force [called "gravity"] that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers."

Oversimplifying, the greater the mass of an object, the greater its attraction to other objects; and the farther apart two objects are, the weaker the gravitational pull between them.

Let's leave it at that!


Read more: https://en.wikipedia.org/wiki/Isaac_Newton

Practice: Match the term to its definition below:

  1. attraction
  2. endeavor
  3. inheres (in)
  4. inversely
  5. mass
  6. mathematical formula
  7. particle
  8. perpendicular
  9. square
  10. time immemorial

  1. at right angles to
  2. oppositely
  3. exists permanently and inseparably in
  4. the quantity of matter in something
  5. a rule or principle written in numbers and symbols
  6. a number times itself
  7. a small bit of matter
  8. drawing power
  9. the distant past, beyond memory or record
  10. effort; activity

Answers are in the first comment below.

Submitted to the Shenzhen Daily for October 26, 2020

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