An antidote to quantum weirdness

January 5, 2008


These pages provide some easily digestible pieces designed to offset the popular idea that quantum physics – the set of rules that describe the behaviour of the material world – is inherently weird and incomprehensible.

The articles make two main points, both of which are very simple:

(1)   The main reason that quantum physics is considered to be weird is a stubborn insistence by many people that the laws of physics must be deterministic, and hence that the unfolding series of events around us is inevitable. If we accept that events in the future are not inevitable, that there are many possible futures, something most of us believe anyway, much of the weirdness that quantum experiments are supposed to demonstrate just disappears. Alternatively, we can see famous quantum experiments such as the Double Slit Experiment and tests of Bell’s theorem as providing evidence that the future is not fixed.

This point is explained more fully in “If only ...”, “Escaping from quantum weirdness by playing cards” and “Phone-ins and quantum physics“.

(2)   The second point can be summarised in several different ways, such as: 

– The fact that we can ask stupid questions does not prove that the Universe is mysterious. 

– It may be fun to discuss questions when nobody can possibly check the answers, but it is not necessarily a good use of your time. 

– What we call “reality” can only consist of information about the world around us. We might like to think that this information gives us glimpses of a sub-reality that forms a satisfying continuous story, but it doesn’t. 

This point is explained more fully in “Escaping from quantum weirdness by watching TV” and “The Grand Final Interpretation of quantum mechanics“. 

A related point is that there is no sharp dividing line between situations where “quantum” and “classical” physics (ie pre-quantum physics) applies. Quantum physics is best approached by understanding that it is firmly connected to the more familiar classical physics – indeed it must give exactly the same results as classical physics in the many familiar situations when classical physics is successful, or it would be wrong.  Like classical physics, quantum physics stands or falls on how well it describes real observations. It is successful because it provides an excellent description of the world we find around us – not of some weird “quantum world” that we invent when trying to answer stupid questions. 

Although it is hard to understand the link between quantum and classical physics when the standard Schrödinger Equation approach to quantum mechanics is followed, it is much easier when using Richard Feynman’s Many Paths (also known as Path Integral, or Least Action) approach. This is explained more fully in “Why quantum mechanics is not so weird, after all.

“Quantum weirdness: an analogy from the time of Newton” makes a comparison between the weirdness expressed about quantum physics now and the weirdness expressed about Newtonian physics in the 17th Century.

Comments and suggestions on these pages should be sent to Paul Quincey at