Question: What is quantum mechanics?

Jack Miller answered on 17 Jun 2013:

Hi Imlaurenpontin,

Quantum mechanics is, roughly speaking, the physics of small things (on the order of the size of a small molecule or less).

It turns out that there is inherent uncertainty of pinning down the behaviour of small things, and that one cannot ever make a perfect measurement. This has lots of very odd consequences — the way nature really works on very small scales is probabilistic rather than certain. We can’t say “there is an electron here in this point in space”, but we can say “there is a probability that the electron is here, and a probability is over there”. This is a very different approach from how things work in everyday life. Einstein famously didn’t like this — he said that “god does not play dice”. Yet, it turns out, that nature really does — and that this leads to odd consequences, with “stuff” being able to act as if it’s in two places at once.

Incidentally, the name “quantum mechanics” comes from the fact that matter on small scales has properties that only come in certain “sizes”, called quanta. So, for instance, an electron orbiting around an atom can have one energy, let’s call it E0, or another lot of energy, E1, say, or a third energy E2…but it absolutely can’t have an energy in between E0 and E1. Its energy is said to be ‘quantised’ — it comes only in discrete units.

Quantum mechanics is behind everyday items such as digital cameras, the lasers found in CD/DVD players, and virtually every single electronic device you’re likely to come across.

For much more information, try having a look at http://en.wikipedia.org/wiki/Introduction_to_quantum_mechanics.

Hope this helps!

— Jack