G8-What Goes Up 800-900L-02

Introduction

You have probably heard the saying, “What goes up, must come down.” At first, the statement seems reasonable, based on your everyday life experiences. You throw a ball high into the air, and it comes back down. Even airplanes fit this model as they take off and then land sometime later. Throughout most of history, the concept of ‘what goes up must come back down’ held true. Fortunately for us, scientists who sought to better understand this phenomenon challenged that notion.

Newton’s Contribution

In the mid-seventeenth century, one man wanted to know more. He wanted to learn more about this invisible force that pulled objects toward the earth. Sir Isaac Newton first published his ideas about gravitation on July 5, 1687. His paper explained that all objects were attracted to one another. In his Law of Universal Gravitation, Newton explained that the force of gravity could be predicted. His model explained how the force is proportional to the product of the two masses. It is also inversely proportional to the square of the distance between them.

Once the force of gravity was realized to be finite, it raised a curious question. Could the force of gravity be overcome? Do all objects that go up have to come back down? His thought experiment involved a hypothetical cannon mounted atop a tall mountain. Newton hypothesized if a cannon ball was launched at a specific speed, it would circle Earth. The speed would need to be just right to assure it didn’t fall back to Earth or fly off into outer space. Too slow and the force of gravity would pull the cannonball down toward Earth, too fast and the cannonball would fly off into outer space due to its own inertia.