4 Physics Concepts Everyone Should Know

What is physics? Physics is the study of matter and the movement of that matter through the space and time of the universe. It’s one of the fundamental sciences, and covers a huge range of subjects. Today, we’re sharing 4 basic physics concepts with you to help you understand this subject.

### The 4 Most Fundamental Physics Concepts

#### 1. Classical Mechanics (The Laws of Motion)

If you’ve studied any sort of science, you’ve probably heard the story of Isaac Newton sitting under an apple tree and formulating the basic laws of motion. While the story is partly apocryphal, there is some truth to it. In 1687, Newton published Philosophiæ Naturalis Principia Mathematica, the first book that laid out the fundamental laws of motion or classical mechanics. In the book, Newton laid out and explained the three fundamental laws of classical mechanics:

1. Objects at rest will remain at rest, and objects in motion will remain in motion at the same velocity, unless the object is acted on by an external force.
2. Force equals mass times acceleration (F = ma)
3. When one object exerts a force on another object, the second object exerts an equal and opposite force on the first.

These may sound a little abstract, but when you think about it, these laws of mechanics are clear from everyday life. On a flat surface, a ball will remain still unless someone kicks it, or the wind blows it. On a hill, gravity acts upon it and pulls it downhill. As far as force, we all understand that being hit by a dodgeball moving 30 mph isn’t the same as being hit by a car moving at the same speed. The mass of the object makes a difference in the force. And finally, we all understand that if we punch a wall, we’re probably going to break our hand. We may hit the wall hard, but the wall exerts an equal and opposite force in return. Ouch.

#### 2. Electromagnetism

What is light? It’s impossible to understand this simple question without talking about electromagnetism, one of the 4 basic forces that govern the universe. Electromagnetism refers to the forces generated by the electrons that are found in certain types of matter throughout the universe. Some types of matter, such as the compounds found in magnets, have electrons that are configured in such a way as to exert force on other electrons that are in “charged particles.”

These compounds exert energy on other “charged particles,” which is why a magnet will attract a paperclip but not your finger. The force carried by an electromagnetic field is carried by photons, which are particles that sometimes act like waves (or waves that sometimes act like particles).

Confusing, I know. The basic thing to understand is that electromagnetic radiation makes up much of our everyday lives. Visible light itself is a form of electromagnetic radiation. Other types of electromagnetic radiation are x rays, radio waves, and so on. Electricity, of course, is created through the manipulation of electromagnetic forces.

#### 3. Relativity

General relativity is a basic concept in physics that is often described using the analogy of a moving vehicle. Let’s say you’re riding in a car traveling at 60 mph. It’s a convertible, and the top is down. You throw a ball directly upwards. Relativity helps to explain the fact that there are two different perspectives on what happens to the ball.

From your perspective, inside the car, you have applied one upward force to the ball. From the perspective of someone outside the car who is standing still, the ball was already traveling 60 mph inside the car when the second force was applied. This is a simple example, but can be expanded to larger scales: for example, the Earth is currently rotating around the sun at around 67,000 miles per hour — but due to relativity, it doesn’t feel like that to us.

General relativity was expanded in the early 1900s when Albert Einstein created special relativity. In his writings, Einstein theorized an “absolute speed limit” for light — a speed which could not be exceeded regardless of relativity. Imagine this: you’re stationary in the middle of space, measuring the speed that light is moving past you. The light source is nearby, stationary. You measure the speed of light as 671 million miles per hour.

Then you conduct two further experiments. In the first, the light source is now being propelled away from you at a speed of 300 million miles per hour. In the second, the light source is moving towards you at the same speed. Each time you measure the speed of the light, however, the number is the same: 671 million miles per hour.

What does this mean? Well, for one, it stretches time: the faster you move, the slower time goes. Yes, this is as crazy as it sounds.

#### 4. Thermodynamics

The study of thermodynamics revolves around the relationship between heat, energy, and mechanical work. Thermodynamics revolves around 4 laws (that for whatever odd reason are numbered zero through three). The laws emerge from a basic interpretation of heat as movement.

At an atomic level, what we perceive as “temperature” actually refers to atomic movement. On a hot day, for example, solar energy excites the atoms in the Earth’s atmosphere to vibrate rapidly. This vibration carries energy which is transferred to our skin, making us feel warm.