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What is quantum physics? Why should we care about knowing what is quantum physics? Do we NEED to know what quantum physics is? How does quantum physics affects our daily lives? These questions, and many more, come to mind when one thinks of quantum physics. Which questions should we try to answer first? We will first settle the issue of know what we are talking about: quantum physics. Understanding the story of the birth of quantum physics will help us understand what quantum physics is.

Quantum physics is the physics of the microscopic world; the world of molecules, atoms, and sub-atomic particles. It is a branch of physics that was born in the early decades of the twentieth century, with its seeds germinating in the late decades of the nineteenth century. Quantum physics was born out of a mixture of failure to understand certain experiments, and also out of non-sense results when applying classical physics to atoms. Yes, physicists were already familiar with the notion that matter is composed of microscopic packets, the atoms. This notion was initially put forth by the Greek philosopher Democritus who postulated that everything is built from atoms and the void. Later on, chemists starting in the eighteenth century with English chemist John Dalton, and after carefully studying chemical reactions and the proportions of reagents that go in and the proportions of the resultant chemicals, correctly inferred that matter is built of individual packets, which he called atoms! Dmitri Mandeleev in the nineteenth century classified atoms by their chemical properties and arranged them into the periodic table of elements that we are familiar with today. We will see as go on with our story that the chemical properties of atoms are a direct consequence of quantum physics!