Quantum Mechanics – Simplified

 

What is Quantum Physics, (and should I be worried)?

‘Quantum’ comes from the single noun, quanta. Max Planck described the smallest meaningful units that can possibly exist in our physical universe.  The smallest possible, meaningful length is known as the Planck Length or Planck Unit.  He also described the smallest unit of energy that can mathematically exist; a quanta of energy. Naturally, he described and proved a tonne of other stuff too, but this will do for now.

Between a heap of brilliant minds with names like Bohr, Heisenberg, Schrodinger and many, many others, physics took a 90 degree turn from logical and sensible; entering an enlightened state where things became really weird.

Light is a good place to start. Physics for ages thought light was only a wave, travelling in ether, an invisible medium, but this was shot down by a simple yet very effective experiment that showed that light followed Einstein’s rules, regardless of direction.  If there was a static medium, it would have to behave differently, with a different speed for light between directions within the ether as our planet moved through it. 

Then came evidence that light was actually made of quanta, tiny particles (bosons called photons). The problem came when evidence showed that light behaves as both waves and particles from carefully constructed experiments. The evidence and only logical conclusion was that light was both, particle and wave, in one state or the other!

Light is emitted as a wave, a potential photon in wave form. Now comes the first freaky bit, when a wave is observed (seen of ‘felt’), is instantaneously collapses into a single quanta of light energy, a photon. Only under observation does a light wave become a photon. Under certain experimental conditions, if can even be seen at different times as both!

Now, a light wave does not travel in a straight line, but takes, in wave potential, all possible paths to its point of observation; yes, this goes against a ‘thrown ball’ kind of logic, but is still true none-the-less. For each photon that we see as light, every possible potential path has been travelled and ‘distilled’ by probability until at the point of observation; only one path has actually been taken by that photon. This is called super-positioning.

Super positioning means that our photon, when travelling as a wave, was potentially everywhere and anywhere; within the rules of light speed, until observed at a specific place. Could it have been observed at a different place? Yes, but it would have been the SAME photon and it would only have taken a single path to get there.

Super-positioning is another non-tactile, non-logical fact of how the universe works at its most fundamental levels.  It is like saying that we can throw one ball to one of a bunch of people, and depending on who sees it first, history then distils into a single trajectory and event from all the possible ones. There were many potential throws made, and only when observed did one become dominant – the most probable – and become reality. Time works in quantum mechanics without a single ‘direction’ as such.

Getting back to the wave-particle thing once more; all electromagnetic quanta (all bosons), some fermions, even some atoms and complex bunches of atoms can be made to experimentally display both a wave and particle duality.  This principle, on the whole, is described as the Copenhagen Interpretation.

Erwin Schrodinger came up with a thought experiment generally referred to as “Schrodinger’s Cat”. For the animal lovers, this was not actually done in experiment; it was a convenient real-world illustration of some very complex maths.  Basically, if you had two cats in two containers, and a single but random event killed one of them, Schrodinger’s argument was that until the lids were removed and the live or dead cat were observed in one container, both containers held BOTH a  living and deceased cat. It was the observation of one that instantaneously cemented the state of both cats.

Einstein called this, ‘spooky action at a distance’ (he was renowned for a quirky sense of humour). Quantum physicists call it entanglement. This is our next stop.

Entanglement is best described by coming back to the atom. For the sake of this description, we will talk about two Hydrogen atoms, each with a single proton ‘orbited’ by a single electron. Electrons have a property called ‘spin’ (their direction of movement). For the sake of this example, we will only use two spin descriptors, up and down. When two atoms are closely associated, they are in a state of ‘entanglement’. The state of electron spin in one will directly and instantly affect the spin of the other electron of the other atom.

Now this principle is technical, but not too challenging to appreciate when two hydrogen atoms are ‘attached’, but here is another freaky bit of the puzzle. Take those two hydrogen atoms to the opposite ends of the universe (about 42 billion light years apart), change and observe the state of one of those electron’s spin, and the electron of the entangled atom on the other side of the universe is changed at that same Planck Interval (arguably, the length of time of ‘now). Oops, light speed does not regulate everything after all!

Information, distinctly describable bits of information, can be communicated without needing to adhere to Einstein’s rule about light speed. This is why he called it ‘spooky action at a distance’, because entanglement uses a means of communication that can’t be described by physics.  It breaks all the rules, but is experimentally proven to exist. Please remember that we are still well within the stuff of quantum physics that is part of the accepted model of the way our universe goes together and works.

The Heisenberg uncertainty principle is another lynch pin of quantum theory. Heisenberg’s uncertainty principle basically tells us we can either know exactly where or exactly when a particle is, but not both.  Only its position or movement can be defined at one time, never both. We can see a thrown ball in the air, and we think we know enough about its position and movement to catch it.  Break this down to the quantum level though, and we discover that things are very much different.  We can imply where and know when, or vice-versa, but not both at a given moment.

So how do we catch a thrown ball?  Go back a few paragraphs to the bit about observing the thrown ball making reality bend to a single history and you start to see why quantum mechanics was a very hard thing for many folks to get their heads around. Time-lines became flexible, and history becomes a flow of data that can be fast-forwarded and rewound.

Next, we need to discuss the Quantum Vacuum, often referred to as the Zero-Point Field. This says that a cube of space one Plank unit on each side without a particle in it must still hold energy – the cosmological constant – another bright idea from Max Planck. The problem comes in that when you actually go into a zero-point, you find both nothing what-so-ever and a huge potential amount of energy, both aspects rapidly approach infinity as you get in deeper. OK, take a breath and let’s try a different angle.

If you find a single point with no matter, no light, no radiation etc.; it still has energy.  This is the cosmological constant. The less logical part of this comes in the form of actually getting into the point where you find both nothing, something and everything, all at the same time. (This is not quite accurate in detail, but accurate in analogy or illustration.)

Why is this important? It is behind this zero-point doorway that super positioning and entanglement works. It is kind of a convenient place for slipping into and out of our linear timeline; where past follows obediently behind now and moves towards the future.

So we have a universe where a particle is not a particle until observed; where light speed governs all matter, but not information; where time builds a history based on future events; where a thing can’t be described in both time and space accurately, and where everything depends on everything else. This, in a nut-shell, is the world of quantum physics.  This is our day-to-day world too!

This brings us to the last section in this fast introduction, that of the inconsistencies and incompatibilities of Relativity and Quantum Theory.

  • http://www.facebook.com/profile.php?id=1719981020 Caleb Sindic

    Awesome stuff!

    • craigberry

      Thank you :-)

  • lguy

    huh! joking to a degree, none the less “Awesome”

  • lguy

    Bear with me please. I know this may sound like a silly question,
    but here goes. This came about through FB conversations with athiests and evolutionists. I am a Christian. Considering the age of the earth as anywhere from 5 – 15 billions years old, according to some, and the number of species on the earth which is anywhere from 2 – 8 million, so the numbers say, one fellow said that there was enough time from the big bang, for random mutations to occur so that we now have life as we see it. Who knows, to me it seems too unbelievable – not enough time if we have to consider how long does it take for beneficial mutations to occur. This, considering that our brain has 100 billion nerve cells alone. One organ out of many in one species, times the number of species that require a similar number of organs, etc. I then watched Amit Goswami on the Quantum Activist. I only know an infinitesimal minute amount of information about quantum mechanics so I ended up on your site and thanks to you have helped to enlighten me some more on the subject. Sorry, no fault of yours, but it is still somewhat confusing – I’m just learning though.
    The question is, what is the understanding about the origins of quantum mechanics?
    Did this process (if I am correct in calling it that) evolve or did it just appear with the “big bang”
    (not saying I believe in the bang), or was it always there, or what??? Thanks for taking the time to answer.

    • Aloysius Flyte

      There has to have been an event to create this, Iguy, to make it all happen. That is how the Big Bang factors into this. That is the conundrum facing physicists today: the marriage of Classical Mechanics / Quantum Theory, and what event supersedes string theory. The process began with the Big Bang, and they’re trying to work out how it fits together

  • just a person named sam

    you guys are so close to the truth that it is almost scary. your on the right train of thought. when you figure it out you laugh at how close this was.

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