What is physics?

    To be honest, it's hard to say exactly what physics is. First of all, physics changes as we progress and make new discoveries. New theories don't just bring new answers. They also open the door to new questions that might not even make sense from the perspective of previous physics. This makes physics more interesting, but it also reduces its definition to generalizations about what physics has been in the past, not what it might become sometime in the future.

    Still, a definition is useful. If you need a definition, this is the one you want. Physicists are essentially trying to:

    Accurate description of the most fundamental measurable quantities in the universe (eg, velocity, electric field, kinetic energy). Trying to find the most fundamental description of the universe has historically been one of the main tasks of physics, as illustrated by the figure below.

    Finding connections between fundamental measurable quantities (eg, Newton's laws, conservation of energy, special relativity). These relationships and laws are expressed in words, equations, graphs, tables, charts, models, and other ways so that we humans can better understand and apply them.

    Source: Tour of the Atom, 1948 General Electric, 1948, George Rousseau.

    Admittedly, reducing physics to just two things is a bit of a gross oversimplification, and it leaves out the finer details of what physicists do and how they do it. But describing the complex world with simple and clear laws is the very essence of physics. So maybe it's not such a bad idea to try to describe the complicated work of physicists with a simple and clear definition.

What will we learn by studying physics?

    In physics, we explain the motion of objects and their causes, but if we don't know how to describe the motion, it's hard to explain it. Therefore, initially in One-Dimensional Motion and Two-Dimensional Motion, we learn how to accurately describe the motion of objects and, in some cases, predict what their motion will be.

    After learning how to accurately describe motion, we will learn how the concept of force can explain why objects change in motion in the topic of Force and Newton's Laws.

    We continue to refine and expand our ability to work with motion by showing that conservation laws are an alternative way to explain body motion. These conservation laws limit the change in motion of a body. We study the law of conservation of energy in Energy and work, and the law of conservation of momentum in the topics Impact and momentum.

    So far, we've studied objects that don't change their rotational motion, and in Moments, Momentum, and Angular Momentum, we'll learn how to describe and explain rotational motion and a new conservation law—the conservation of angular momentum.

    We will then apply our knowledge of motion, forces, and the laws of conservation to consider several new forces and phenomena. In the topics of fluid physics and thermodynamics, we learn to work with liquids and gases. Then in Electricity and Magnetism, we will learn about two new forces, electric and magnetic forces. In electric circuits, we learn how electric forces cause current to flow. In optics, we study the laws of refraction and reflection of electromagnetic waves (ie light). After learning about light, we will explore Einstein's Special Theory of Relativity. And that's not all.

    By the end of the topics, you will have a good idea of elementary physics and the mathematical tools physicists use to describe and explain the universe, but no summation can describe all the interesting and powerful aspects of physics. The best way to find out is to see it all for yourself.