Before Isaac Newton, people believed an item was always at rest. Newton utterly refuted this widely accepted notion in the 1600s. He observed planets and stars for a long time, so he concluded that they were continually moving to one another. For instance, the solar system rotates around the galaxy while the Earth continuously orbits the Sun.

Newton created three laws to explain how all objects in the universe move. According to the first law, if no other force acts on an item, it will continue to move in a straight path. Galileo conducted an experiment in which he rolled balls down a hill to illustrate this. The only force acting on the balls was gravity, which caused them to roll straight.

According to Newton's second law, an object will accelerate at a rate inversely correlated to the force applied to it. For instance, a car with a stronger engine will accelerate faster than one with a weaker engine. According to this rule, a force will have less impact on a body's motion if it has more mass. For instance, if two vehicles have the same engine, the heavier vehicle would accelerate more slowly.

Newton’s law of universal gravitation describes gravity. It says that every object in the universe pulls on every other object with a force. This force depends on the masses of the objects and the distance between them. The greater the masses, the stronger the pull. Mathematically, this means that if you double the mass of one object, the gravitational force doubles.

In general, scientists gather information from observations they make during experiments, for instance, and use it to create theories. Theories have two major advantages. Firstly, they enable scientists to predict what will happen in the future. For instance, Newton's theory of gravity made it possible for scientists to forecast the future motions of celestial bodies like planets. With the help of the theory of gravity, it is feasible to predict anything, even the place where Mars will be in six months.

Scientific theories are not “proven” in an absolute sense. They are supported by evidence and can be revised or replaced if new data contradicts them. For instance, the idea that the Earth is the center of the cosmos was formerly widely accepted. Galileo’s discovery of moons orbiting Jupiter showed that not everything revolves around Earth, providing strong evidence against the geocentric view.