Quantum Mechanics

Bet you never thought you would see that heading in this blog.

I have read many books on this subject and after all that all I have managed to get is some kind of intuitive feel for the subject. The basics seem fairly simple. At very small sizes i.e. a few dozen atoms or smaller, things are observably different. Some have heard of the Uncertainty Principle, the Schrödinger Equation and so on but to really give an example of how bizarre quantum mechanics is you need to remember back to high school physics and the double slit experiment.

If you remember you shone a light that hit one or two slits and projected this on a background. When two shits were open and interference pattern was formed, because light has the characteristics of waves (and of particles). When waves interfere you get lighter and darker places because the waves either reinforce each other or cancel each other out. So far most people can follow this kind of description and logic. With the single slit open you get a bright spot in the middle gradually getting dimmer as you spread out, again fairly obvious.

Now instead of a light you start firing individual photons (the smallest unit of light) at the slits. In this case they are behaving like particles. In fact this experiment has been duplicated using atoms and bucky balls (carbon or boron atoms in a ball like structure C20, C20 etc.).

Particles are not waves so there can be no interference pattern, but at relativistic speeds (close to the speed of light) matter starts to behave like a wave. To make sure you fire one particle say every second. When both slits are open, over time, the interference pattern is still created!

My first question when learning about this was, "how does it know?" and started imagining intelligent photons and the like. People far smarter than I am use terms like probability, all possible paths and then pages of mathematical equations. The experiment is repeatable and probabilities are predictable and verifiable. Getting your head around just this one experiment however is a very difficult thing to do.

The theory says that with a large slit if you could fire elephants at the speed of light through them you would get the same, albeit messier, result.

Then there is quantum entanglement where two particles can be linked together and instantly react to each other across distance a seeming violation of the speed of light. The latest theories posit that all matter is ultimately made of of random quantum fluctuations in a vacuum. Basically we just don't know.

So why is this topic in the blog? Well if you think about it sometimes it is nice to know that our universe has even more bizarre things that deaths caused by bushfires, the problems with Islam and the weird machinations of our governments.

So take a few minutes to ponder the weirdness of the quantum world before you have to turn your mind back the the weirdness that is our world. If you want to learn more about this field I can recommend Dirac's lectures and for a broader overview Brian Greene (both his books and his DVD)