Thursday, 15 September 2005

Quantum Mechanics is Real

Last Friday I heard something from a student that I hear from a lot of people and makes me very upset. He said that "quantum mechanics is so abstract that it is not related to the real world". Ok, he's only fourteen, but the others were not so young. It is unbelievable that more than a century after the advent of quantum mechanics people still think that it is only a bunch of complex rules with no aim or utility! People only need to look around to see how quantum mechanics is TOTALLY related to our daily lives.

Computers are machines that are used everywhere, everytime. They are constructed with transistors, and transistors are quantum devices. Nuclear Magnetic Resonance (NMR) is a quantum mechanical device too. But the most quantum of all devices is also the most common. You can even buy it in any market. The LASER. Lasers are used to do so many things today that a complete list would take pages to write. The laser was originally created without any application in mind. Just an experimental exercise of quantum mechanics. Lasers CANNOT be even explained by classical optics. They need quantum mechanics to exist. I think I am not exaggerating if I say that computers and lasers are the basis of our modern technology. Therefore, our modern technology IS quantum mechanical.

Quantum mechanics is the most respected physics theory. There is not a single experiment today that contradicts quantum mechanics. The only problem with it is a philosophical one: its interpretation. The mathematical framework of QM is internally consistent and using it we can make predictions for experiments that are confirmed to one part in one billion! But as we cannot probe the diminute distances that are the range of applicability of QM directly with our senses, a picture of what is happening is difficult to construct. But (although a lot of people will disagree with me in this point) pictures are less important than the mathematical formalism. That is because we can test experimentally the theory even without a clear picture if we have a precise formalism that allows us to predict the outcome of experiments. And predicting what Nature will do on a given situation is what science is all about!

Next time you think about saying that QM is just nonsense mathematics & physics, look at your computer and your CD-player, remember about NMR and laser pointers, and give a look at the myriad of medical procedures that use one or more of the three devices I described above. And before saying anything, think seriously if you could really live the way you live today without QM.

The picture in the beginning of the post is a computer representation of orbitals in a hydrogen atom calculated using QM.

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