Thursday, January 21, 2010

Quantum Mechanics Primer

Quantum mechanics is one of the most peculiar, counter-intuitive and interesting physical theories that has ever been developed by science. The world of the very small has only been accessible for approximately one hundred years. This relatively short period has spawned a wealth of knowledge highlighting the elegance and subtlety of the natural world. I am going to go over the history and the very basics of quantum physics before I try to tackle some people who misunderstand (or are simply con artists) and misrepresent the science to suit their purposes.

History and Background

The transition from classical to quantum mechanics began at the turn of the 20th century. Like all paradigm shifts in science new discoveries and thinking led to inconsistencies with current models. In this case it was black body radiation. This radiation is emitted by all objects with a the frequency is directly dependant on the object's temperature. It is the phenomenon that causes stove tops to glow red as the radiation distribution transitions from the invisible infrared regime to visible light.

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The theories at the time didn't match up with observations as the temperature reached the ultraviolet regime. If light was treated classically an infinite amount of energy was predicted to be released as the formulae showed an increase in energy proportional to the square of the frequency. The solution of this problem was to re-examine some of the premises the incorrect theory was based on.

Einstein and Planck developed the idea that instead of being continuous as before light was divided into packets called quanta. Each of these "pieces" of light required a certain amount of energy to be created which increased with the colour. Since it would take a lot of energy to create lets say X-rays they wouldn't be significant until temperatures reached very high values.

This discovery led to the first major revolution in the physical sciences since Newton. Many other well known scientists jumped into the fray and completely transformed our view of the physical world.

Photons were now seen as a particle. However the theory also had to reconcile with previous observations that showed, without ambiguity, that light also had wavelike properties. The answer turned out to be that indeed photons and, as was later discovered all matter, has properties of waves as well as particles. It is hard to picture this simply because our brains evolved to do different things than study QM. It would be rather anthropocentric for us to think that nature has to behave in ways that we can comprehend intuitively. Instead math provides us the gateway to learn, make predictions, test and ultimately utilize the world of the very small.

All matter therefore is "fuzzy". Instead of saying a particle is at a certain location we can only give a range of probabilities of its location. Another interesting emergent property is that particles can tunnel through barriers forbidden by classical physics. A decent analogy of this would be to imagine a ball rolling in a frictionless half-pipe getting near but never past the lip. Classical physics says that this ball will roll forever but quantum mechanics says there is a non-zero chance that the ball will tunnel through the half-pipe. It is important to not take this analogy to literally as macroscopic objects don't do this. The probability of this happening on an actual half-pipe is effectively zero. Many electrical process however have to take into account this tunneling current especially now that transistors on some silicon chips are around 45nm in size. The fact of the matter is that at the macroscopic scales we live in these effects are no longer apparent as the large number of particles are "smoothed out" and the wavelike property doesn't exist for all practical purposes.

Quantum Mysticism

Unfortunately due to the relative complexity of the math behind even basic quantum mechanics (2nd order PDE's) it typically isn't taught until the second or third year of an undergraduate physics program. This leaves the vast majority of the population in dark when claims are being made about the subject. It is a perfect storm, hard-to-understand theories and people ready to take advantage of that; most people don't believe that you can fall through your chair, you can co-exist in two places at once or that your thoughts can directly affect reality until the word quantum is brought into the sentence.

The popular docu-drama "What the Bleep do we Know?" is probably the most notable example on film. It blends real science, analogies and pure bullshit. When you start digging deeper the movie begins to unravel. The main individuals behind the movie are all from Ramtha's School of Enlightenment. A sort of new-age school/cult founded by J.Z. Knight. This person claims to channel the spirit of a Lemurian named Ramtha who led an army of 2.5 million to battle the Atlanteans 35 000 years ago. Yeah...

Of course their background doesn't necessarily make their claims false. Instead their backgrounds and fundamental beliefs are wholly inconsistent with reality as we understand it, dead people don't talk to living people and the estimated human population was around half of the size of the army he supposedly led. This should lead you to more skepticism of their claims. Maybe they have discovered the secret to life, the universe and everything but until they actually drop down some real evidence their claims are just crackpot assertions.

Now looking at the actual thesis of the movie, namely that because of the laws of quantum mechanics you can control the world around you with your thoughts. The basic law they are butchering is the Heisenberg Uncertainty Principle. It states that in nature some quantities cannot be known with arbitrary precision at the same time as certain other quantities. It extends to more than this but lets look at the most common case, momentum and position. The more you know about one quantity the less you can know about the other. This isn't a limitation on technology it is a fundamental law of nature the more precise in one measurement, the less precise the other is.

A basic explanation of this can be thought of by incorporating the act of measuring. When we look at a ruler we only get information because light is transmitting it. Now imagine the ruler was much much smaller. If each particle was a marking on the rule the light may actually have enough energy to push the particle and change its state. The act of measuring the system, the transmitted photon of light has caused the system to change. But remember a person doesn't have to be present, all that has to happen is particle interaction.

The movie takes this and tries to elevate this concept to consciousness. They take "observer" and link it to a human being. This is a huge leap and ultimately a non-sequitor. Quantum mechanics says nothing about human consciousness influencing measurements. They made it up. Their argument disintegrates when the primary premise of the movie, that we can change reality with our thoughts is shown to be based on, instead of established science, pure conjecture.

I haven't gone through most of the movie, if you are interested there are plenty of skeptical take downs of it. I only want to get people thinking about how others will take advantage of complex scientific topics such as QM and consciousness. They are both fascinating topics on their own, you don't need to make shit up. The fact that we don't fully comprehend the two doesn't mean we won't understand them in the future or that quantum mechanics won't play a roll. If there is a significant link between quantum mechanics and the brain I am quite confident it will be much more subtle and elegant than this magical thinking.