Science Experiments | Gravity - Introduction

Introduction

Earth orbits the Sun. The Moon orbits the Earth. But how do the planets stay in the sky? How do we stay on Earth's surface? Englishman Sir Isaac Newton (1642–1727) figured out the answers to these questions while watching an apple fall in his orchard. Newton reasoned that the force that pulls the Moon into its curved path around Earth instead of a straight line was the same force that pulled the apple to the ground. Newton was a scientist and mathematician, and he wrote his theory on a scrap of paper, something he did with all his thoughts and formulas. The falling apple initiated his famous universal law of gravityThe law of physics that defines the constancy of the force of gravity between two bodies., which states that the attracting force between any two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. It was published in his book Principia in 1687.