Quantum Physics

Quantum Physics is a science of the very small. Quantum mechanics describes the behaviour of matter and its relations by energy on the scale of atoms and subatomic particles. By distinction, classical physics only explains matter and energy on a scale conversant to human experience, including the behaviour of astronomical bodies such as the Moon. Classical physics is still used in ample of modern science and technology. However, towards the end of the nineteenth century, scientists discovered occurrences in both the large (macro) and the small (micro) worlds that classical physics could not explain. Coming to terms with these limits led to two major revolutions in physics which created a shift in the original scientific model: the theory of relativity and the development of quantum mechanics. This article describes how physicists discovered the limits of classical physics and developed the main concepts of the quantum theory that replaced it in the early decades of the twentieth century. These concepts are described in roughly the order in which they were first discovered.