My name is James Lincoln. I'm a physics teacher here for About.com. Today, we will be discussing several physics terms that you will need to know if you want to study physics.There are several constants to know, but three of them tend to be considered "Universal Constants." These are the three constants that would be the same anywhere in the universe, for any creature in the universe, or in any universe, period. These three are the speed of light, Newton's Gravitational Constant and Planck's Constant.The speed of light is how fast light or any interaction travels. It's sometimes known as the Einstein Constant. Newton's Gravitational Constant allows you to predict how strong gravity is between two objects in space. And the third one, Planck's Constant, let's you know how much energy can be exchanged between any two atomic or molecular systems.A major area of physics is quantum mechanics, which is the study of very small particles. The reason we use the word "quantum" is it means we are counting the particles. Now, what's unusual in quantum mechanics is that you can't actually make good predictions about a single particle, so you have to quantify the probability of several particles at once. Einstein's Theories of Relativity are special cases in which objects are moving very quickly, near the speed of light, and unusual phenomena occur, such as changes in length, changes in mass, or changes in time. In the general relativity, very large masses will warp space and cause light beams to bend and gravity to exist.Duality is an idea that came out of quantum mechanics. The idea is sometimes particles will act like waves and waves will act like particles. Another idea in physics is that of a field. A field helps explain the way gravity or electric forces or magnetic forces reach across empty space to cause pulling and pushing of other objects. Inertia is not just mass, it's an idea. It's the idea that when an object is moving, it's in its natural state, to keep moving. And when an object is at rest it is in its natural state to remain at rest. I'm James Lincoln for About.com. Thanks for watching.