Quantum mechanics is weird - Discoveries in this field have been wonderfully counter-intuitive, prompting the legendary Niels Bohr to state "..those who are not shocked when they first come across quantum theory cannot possibly have understood it.". In fact, so profound are some of the questions it raises about reality that the ineffable Richard Feynman once said "I think I can safely say that nobody understands quantum mechanics.". Because the subject is so incredibly jaw-droppingly at odds with what we're used to in our macroscopic world, the fact that the microscopic behaves quite differently dazzles people.
But it is this very dazzling property that has made purveyors of nonsense grasp it, and use it as a stamp to justify their outlandish claims. The field of quantum mysticism and quantum healing is the use of modern physics terms to lend weight to a loose connection of new age and spiritual jargon, totally mangling the beautiful science in the process - Works by Deepak Chopra, Robert Anton Wilson, Gary Zukev et al have offered quantum mechanics as some kind of magical deus ex machina to explain away any gaping holes in their new ages drivel. Only here's the kicker - invoking quantum mechanics to 'explain' these, or indeed any human experiences is so stupid, it's not even wrong. So I decided to write a post condemning these utter quacks, when I came to the realisation that starting off that way might deny my readers an insight into the utterly crazy world of quantum mechanics. So I decided to split the post into two, with the first part a quick crash course into the brain shaking world of the very small and some other time I shall do a follow up on why new-agers and quacks love the word quantum and how they get it wrong everytime....
|Einstein reacts to Deepak Chopra's latest take on Quantum healing...|
|Newton - Would often be found musing over Optics and less often over the hottest trends in wig fashion|
|Slinky dog - Subtly teaching us about wave mechanics, the crafty informative bugger..|
|We are the physicists and we seek the aether!|
Just one small problem...
There was just one slight problem - the aether didn't exist. This was shown by the famous Michelson-Morley experiment, the most famous null result in physics. The ramifications of this experiment and a curious derivation from Maxwell's equations led a young patent clerk from Germany named Albert Einstein to a truly wondrous theory called special relativity in 1905, a fascinating area with an intimate relationship to quantum mechanics but at the moment we'll leave it be and jump to the world's most obscure light bulb joke.
|Wait for it....|
From Hand waving to mind blowing...
A "quanta" merely refers to a discrete packet, so it was apparent Planck's solution had 'quantised' energy. At this point no one gave this quantisation of results much notice, including Planck himself. They figured it was some problem with the model. Models, after all, are approximations of reality. But for Einstein, this actually solved a problem he'd been musing on called the photoelectric effect. This effect is observed when high energy light, even at low intensity, causes a metal to eject electrons. But curiously, lower energy light, even at high intensity couldn't dislodge them. This makes no sense in classical physics - if you imagine light like a wave lapping away at a sea cliff; a lot of little waves have the same cumulative effect as a few powerful waves. Yet this wasn't happening - only certain energies were doing it, intensity didn't matter. Einstein solved the puzzle by deducing that the light was arriving in packets which we know call photons. If one of these packets had enough energy, an electron was emitted. Einstein had used Planck's guess to solve a totally unrelated problem, and had begun to show that light was a particle.
So here was Einstein in 1905 postulating that light was a particle, and making a pretty damn convincing case for it. But this kind of flew in the face of previous experiments and theory - Young had shown light was a wave. Maxwell's equations worked, and relied on light having wave properties. Waves and particles are mutually exclusive, what in the name of Schrodinger's fond regard for animal welfare was going on ?
|Is this really the only way to demonstrate the madness of macroscopic observer effect Dr. Schrodinger ?!|
Stop for a second - if that isn't making your logical brain go into convulsions, think about it again - it is something of a paradox of modern physics. What's more, there is a further principle which physicists call complementarity that essentially states something equally weird - while the wave and particle nature co-exist, any attempts to measure the properties of one state destroys all information about the other state. More correctly, the twain properties can never be measured at the exact same time.
This is deeply weird, and equally, deeply wonderful.
|Niels bore, the third most famous and great Dane after Hans Christian Anderson and Scooby Doo|
Einstein takes his quantum ball home
Now, physics up to this point had been deterministic. If you knew all the variables, you'd be able to always predict the output. But new quantum theory suggested that at the very, very small end of the scale, events were probabilistic. These probabilities were related to the square of the wave function, Ψ, of the system. Werner Heisenberg also showed that there was an inherent uncertainty in some variable pairs, such as position and momentum and energy and time - there would always be an uncertainty in these measurements as they involved the interaction of the system and the measuring device. This relationship was verified and is now known as the uncertainty principle. These ideas taken together for the basis of what is called the Copenhagen interpretation of quantum mechanics, which postulates..
- A system is completely described by its wave function Ψ
- Nature is essentially probabilistic
- It is impossible to know the value of all system properties at once (uncertainty)
- Matter exhibits wave-particle duality, both cannot be measured at once (complementarity)
- Quantum mechanical systems will reproduce classical results for large systems / particles
This interpretation of quantum mechanics is the most common, but there are others, differing mainly on the nature of the wavefunction. Now, a system can be in a superposition of all possible states, but the act of measuring them forces the system to collapse down to a single measured state. This bizarre behaviour is called wavefunction collapse, and is still a hotly contested question. In the Copenhagen interpretation, the measurement 'forces' the system into one state, where as the in the 'Many worlds' interruption, each possible state exists in a different universe. There are dozens of interpretations of Quantum mechanics - note that the the predictive power is beyond dispute, but the philosophical question of what these results imply about nature itself is still a thorny issue.
But ironically, the man who had lead the world into the quantum revolution loathed the new formulations - Einstein did not at all approve of the probabilistic interpretations, preferring a version of the ensemble interpretation which argues the wave function doesn't apply to an individual system but only to groups of them. This is when Einstein famously argued "God does not play dice!". Legend has it that Bohr muttered he should stop telling God what to do.
Bohr and Einstein had a series of debates, and every example he gave Bohr was able to counter. Finally, Einstein along with some colleagues came up with the EPR paradox - a quantum system has a wave function, but if this system is split into two, the system still maintains one wavefunction between them. Then, if you performed a measurement on one of them, even separated by vast distances, the other would be forced into a state too. Einstein and his co-authors argued that there must be a class of 'hidden variables' that told each particle what to do. QED, thought Einstein, as the other idea meant that non-local effects could instantly travel seemed utterly absurd on the face of it.
|Smug Einstein - QED, bitches!|
|Nice kitty, GET IN THE DAMN BOX!|
Class dismissed - some concluding remarks
The world of the very tiny behaves nothing like the world we know, and at small enough scales quantum effects dominate. What puts the limit on this scale ? The limit is related to a constant of nature we know as Planck's constant. It is given by..