reply to post by Spiramirabilis
I don't know if there is any such thing as a good popular account of quantum mechanics. Richard Feynman, the originator of the theory of quantum
electrodynamics and a legendary humorist, observed that 'if you think you understand quantum mechanics, you don't'. These wise words should serve
as a warning to
any layman hoping to get a grip on this terrifying subject without any training in physics and mathematics.
If that doesn't put you off and you are determined to plough ahead regardless, I salute you. Here are a few things you should know.
- Quantum phenomena occur on a very, very small scale, known as the Planck scale. How small is
this? Well, a unit of Plank length is 1/10,000,000,000,000,000,000 times the diameter of a proton, or roughly
3/500,000,000,000,000,000,000,000,000,000,000 of an inch*. The consequences of a single quantum event can sometimes be detectable at the human scale
(as in the Schroedinger's Cat thought-experiment or the operations of 'tunneling' electronic devices), but the sum of the unimaginably vast numbers
of quantum events constantly occurring is very simply the real world, which follows the laws of classical (relativistic) mechanics. Thus fundamental
uncertainties at the quantum level are eliminated and the universe is apprehended as deterministic**. This process, which some explain as
decoherence, is part of the great scandal of quantum mechanics, otherwise known as the
- observer effect. This is the one thing everyone thinks they
know about quantum mechanics, which is that quantum outcomes are affected by the act of measurement. It is scandalous because it demands the presence
of an observer to make reality real. But the quantum observer effect is also - and here's the crunch - inoperative on scales larger than the
Planck scale.
- You may also be surprised to learn that, although quantum theory has been borne out by countless experiments, it is in some sense flawed or
incomplete. The observer effect is one indication of this, as I pointed out in an earlier post: things happen anway, whether someone's around to
observe and measure them or not.
- The other indication is that, put very simply, quantum mechanics does not agree with general relativity, another theory which has been massively
substantiated by observation and experiment, and is moreover far more consistent in itself and its predictions than quantum theory is. All quantum
events are described as taking place against a fixed universal background. But the real world is not like that: space and time are in constant flux
under the influence of gravity. There is no fixed background.
None of this states that quantum thory is wrong; merely that it is incomplete, or a special case of a more general theory, just as Newtonian mechanics
is a special case of general relativity in which certain values are constrained.
There is no complete theory of the world in physics -
supersymmetry, supergravity, string theory, M-theory and all the rest have enormous caveats atached to them. The scary truth is that there has been no
progress on a real, falsifiable theory of the world since the late 1970s. In fact, with the discovery of dark matter and dark energy and the
increasingly weird behaviour ascribed to black holes, confusion has been worse confounded.
Remember all this when you crack the covers of that book of yours.
The phrase 'quantum physics' is not wrong, but when I hear it used by a layman, my antennae always prick up, because in the nonscientific world
'quantum physics' is code for wish-fulfilling pseudoscience that has nothing to do with quantum
theory or quantum
mechanics. In
'quantum physics', free will is made possible by Heisenbergian uncertainty in the operations of 'microtubules in the brain', water has 'memory'
and willpower can alter reality.
Quantum theory does not predict or support any of this.***
* * *
Why do you want to learn about quantum mechanics? Do you intend to make a career of it, or are you simply very interested in physics? If you're
really interested, you'll find some book recommendations
here and
here. The Shankar and the Dirac are classics - Paul Dirac was one of the founders of
quantum mechanics. However, the book mentioned by the OP in one of those forums, Zukav's
The Dancing Wu Li Masters, is mystical tosh. Neither
the physics nor the Eastern philosophy in it are to be trusted.
If you're interested in the philosphy of quantum theory (I mean philosophy in the academic Western sense) I'm afraid I can't help you much.
And if your interest is chiefly in spiritual things, my advice is to stay away from quantum mechanics. Truly, it has nothing to offer you. It is about
vanishingly tiny and quite possibly nonexistent particles crashing into each other. It is an incomplete theory and almost certainly
not an
accurate description of the real world. Forget about it.
*I hope I got all the zeros in. For those who wish to check, the respective figures are in fact 10^-20 and 6.3 x 10^-34
**Hence, no free will (again!)
*** Specifically, it does
not make it possible to change the world through willpower.
[edit on 5-9-2008 by Astyanax]
).
