# Newton's Discovery of Physics

By Jorden Simmons

Topic: History

[Open the interactive Jig](https://ask.jig.com/j/hr1p7BYd8LYr)

## Guide

### 1. A quiet farm, 1666

In 1665 a deadly plague closed Cambridge University\. Young Isaac Newton went home to his family's farm at Woolsthorpe\. For about eighteen months he read, wondered and worked things out on his own\. He later called it the prime of his life for invention\.

Drag empty space to turn the diorama\. Pinch or scroll to look closer\.

### 2. Why does an apple fall straight down?

Newton said that watching an apple fall in the orchard set him thinking\. Why does it always drop straight down toward the middle of the Earth, never sideways or up? Tap the red apple to let it fall\.

No one at the time said it hit his head\. That part was added later\.

### 3. Does the pull reach the Moon?

Newton wondered whether the same pull that brings the apple down might stretch all the way up to the Moon\. If it did, it could be what keeps the Moon circling the Earth instead of flying off into space\.

The Moon goes once around the Earth in about 27 days\.

### 4. Newton's cannon

Newton imagined a cannon on a very tall mountain\. Fire it gently and the ball curves down to the ground\. Fire it faster and it lands farther away\. Fast enough, and the ground curves away as quickly as the ball falls, so it falls around the Earth forever\.

That is an orbit: the Moon is always falling, but always missing\.

### 5. Weaker far away

The Moon is about 60 times farther from Earth's centre than we are\. Newton worked out that the pull must get weaker with distance: 60 times farther means 60 times 60, or 3,600 times weaker\. That weaker pull fits the Moon's 27\-day trip very well\.

Here the distance is drawn to scale: each small bead is one Earth radius\.

### 6. Splitting sunlight

Newton also studied light\. In a darkened room he let a thin sunbeam through a small hole in the shutter and into a glass prism\. Out came a long band of colours, about five times longer than it was wide\. Switch on a second, upside\-down prism to see what happens\.

Red bends the least and violet bends the most\.

### 7. One law for the heavens

In 1684 the astronomer Edmond Halley asked Newton how planets move\. Newton's answer grew into a great book, the Principia \(Latin for "principles"\), printed in 1687\. Its three laws of motion and one law of gravity explain falling apples, the Moon, the planets, comets and the tides\.

Halley paid for the printing himself\.

### 8. Back in the orchard

Newton did not find all this in one flash\. It took about twenty years of questions, experiments and careful mathematics, building on Galileo and Kepler\. The apple and the Moon feel the same pull, and so do you\.