Just what IS Quantum mechanics?

This is a question that has been been asked many, many times.

Now, let's get one thing perfectly straight - the "mechanics" bit up there bears no resemblance to the kind of mechanics we usually talk about, such things as engines, nuts, bolts, screwdrivers, wheel- balancing, etc.

True, it is the same word, but in physics it means something very different and quite specific: "mechanics" in physics is nothing more than the study of the relative movement of things, like apples dropping from trees, billiard balls moving on a snooker table, and the occasional hammer hitting someone's head.

Nothing to do with cars or anything Richard Anderson might say in "Forbidden Planet".

A lot of the time, mechanics just deals with things hitting each other. When I say "deals with" I mean we use equations to find out where they will go next.

For example, what happens when two billiard balls collide, head on? Well, if one is standing still, the moving one hits it and transfers the motion, and the second one moves off.

In an ideal world, yes, but this is not what happens. It so happens that both balls end up moving. "How can this be?" I hear you ask. The answer lies in the way the balls are put together and what they are made of, BUT that is the realm of materials science, not physics.

So mechanics is when things hit other things. Now we're getting someplace, as Ollie would say.

There are different types of mechanics, all of which use the basic "mechanics" laws set down by Isaac Newton. There is Celestial Mechanics (how large things like planets behave), Terrestrial Mechanics (hammers hitting heads), Car Mechanics (nothing to do with this discussion), and Quantum Mechanics (how very small things behave, things like atoms, etc). Oh and there is Relatavistic Mechanics, and Relativistic Quantum Mechanics, too, but both these only come into play when you are travelling just a tad faster than Richard Hammond did last year.

So, WHAT is Quantum Mechanics? We, like I said, it is "how small things behave" but there is more to it than that. Scientists thought terrestrial mechanics ruled ok, ino questions asked, including the very small. The fact is, we had to invent a completely new branch of Mechanics, so as to predict where things ended up after the charabanc. The reason was, the very small particles acted in very different ways to what we expected. They actually acted like "waves". Hard to believe , ain't it? Moreover this "quantum Mechanics" gave right answers for all the other mechanics branches as well.

Depending on the experiment you were doing , the very small particles act both like "waves" and "particles". It is very hard to imagine, and even to this day 99% of scientists don't really know what is going on, BUT, what they DO know is how to predict what will happen when two of these "quantum" billiard balls collide, and what happens afterwards. Very clever.

So where does that leave us? Well, to the ordinary layman, you or I, it means nothing, because we as people are never going to deal with things THAT small ( I am saying nothing about Marvin's brain here), but some scientists have to deal with this every day.

They are called "particle physicists" and live in very tall ivory towers in Geneva. I, the layman (or laywoman) deal with particles just as small, but I am only called a lowly "nuclear physicist".

However, I still find fun mucking about with the equations in our computer programs, investigating "Quantum Mechanics". It is almost all a little girl can do.......

So, when it comes down to it, we have a perfectly good representation of the world as we know it with "Terrestrial Mechanics", so why do we need "Quantum Mechanics"?

A good question, and one which deserves an answer. With no Quantum Mechanics, we would not have discovered Light Amplification by the Stimulated Emission of Radiation, or the LASER. There would be no nuclear or particle physics, ie neither the Atom bomb nor the Hydrogen bomb would have been invented. Is that a good or a bad thing (bad for me, anyway!) - one for the philosophers, I am sure.

Another thing is that wihout Quantum Mechanics, we would have primitive computer controls still, the most important of all would be - no DVD's CD's etc, Guided missiles would be out too, as would be supermarket checkouts. TV remotes. The road goes ever on.

Maybe the most important thing we would be missing would be the Josephson Junction in electonics, but I wll leave the reader to find out what is THAT by himself.

Shrodinger will never know what a Pandora's Box he opened!