Quantum physics has always been this mystical thing to me.  Throughout my years of academic studies in engineering, the word quantum may have been uttered by a professor, but it was never explored in any kind of depth.  Engineers are practical, and while quantum physics is fascinating, it is of little practical importance to most engineers at present.

A physics professor might say, "Classical physics is not theoretically sound, as it is only an approximation, and may only be accurately applied to things that do not move too fast and are not too small."  An engineering professor might then respond, "Most things are reasonably large and move reasonable slowly... In any case, any error less than 5% is good enough for me."

For nearly all engineers, the entire field of study may be ignored, and is.  For theoretical physicists on the other hand, it appears that there is not much outside quantum physics to ponder anymore.

In reality, for an object of reasonable size, the amount of error introduced by simply ignoring quantum aspects is negligible.  Still, this field of study is so fundamentally different from all of the science that came before it, that it is always categorized separately; that is, there is quantum physics, which centers around wave functions and probabilities, and then there is classical physics, which is everything else.

Quantum physics originated in the mid-1920s with physicists such as Max Planck, Albert Einstein, Neils Bohr, and Werner Heisenberg.  The fundamental principle of quantum physics was discovered by Heisenberg, who showed that one could not be 100% certain of both the momentum and position of a given particle.  The law is known as the 'uncertainty principle', not to be confused with the 'what the heck is going on principle' commonly exemplified by certain physics students.  

I remember the moment when I realized that I liked physics.  I was sitting in my grade 11 physics class learning about projectile motion.  When the teacher explained that you could determine where and when a ball thrown from a specific location with a specific velocity would land, I was hooked.  Predicting the future with certainty - what an empowering notion.

Had I learned that a given circumstance has a wide variety of possible outcomes, as quantum physics shows, the allure of physics would have been greatly diminished for me.  Another downside about quantum physics, is that its concepts are hard to wrap one's head around.  My distaste for quantum physics probably stems from the fact that it is less connected to our every day life experience than are other aspects of science.  Also, I was never formally introduced to it in an academic setting, and so perhaps I associate my quantum discomfort with a  lack of familiarity - I may warm up to this branch of science in time, like a father might a son-in-law.

If you are like me, and find quantum physics to be somewhat unsettling, do not feel bad, as we are both in good company.  Einstein famously rejected quantum physics, stating that "God does not play dice".  It was a powerful and memorable line, but was refuted by an even better response from the quantum community: "Stop telling God what to do!"

In the end, it is somewhat ironic that Einstein did not support quantum physics, as he is indeed one of its founding fathers.  Einstein received the Nobel Prize for physics for his development of the photoelectric effect theory, which showed that light behaves as a particle - this notion got the quantum ball rolling.

The term quantum was coined by Max Planck from the root word "quanta".  It describes a finite, minimum currency for energy.  It is like the dollar currency system, which does not allow physical exchanges of money by fractions of a penny.  You can have no money, or you can have one penny, but you cannot possess any amount in between.  Similarly, a particle of light (photon) can have no energy, or it can have E = hf (where h is Planck's constant and f is the frequency of the light), but it cannot have hf/2 of energy, for example.

It is a truly fascinating disconnect between most physicists and engineers: the first group believes that quantum physics is the only truth, and the second group shrugs their collective shoulders.  Most engineers work on a macroscopic scale.  Unless you are an engineer specializing in semi-conductors (and there are a few), the effects of quantum physics on your work are likely to be insignificant for now.

That being said, the scientist within me has his curiosity piqued by one particular area of quantum research: quantum computers.  In this semester alone, a few physics students have independently brought the subject to my attention without being prompted to do so.

Quantum computing was introduced by Richard Feynman in the early 1980s.  The concept is a computer that takes advantage of certain quantum mechanics phenomena.  The end goal is not so surprising: a CPU that can operate much faster than any of the traditional transistor-based variety can.  I am always simultaneously fascinated but also concerned at the prospect of "smart" computers, as the very notion is indicative of a technological singularity.  We humans will know our time is short once robots start building smarter robots than themselves.

I turns out that I am not only uncomfortable with quantum phenomena, but also fearful of the technologies that they may lead to.  Maybe I will just go on avoiding quantum physics, and attribute my disregard to the uncertainty principle.

What am I?  There are many ways to answer this philosophical question, but let us take a scientific approach.

The universe is composed of indivisible building blocks.  An electron is one example of such a building block, and physicists today seek to find other yet unknown examples of such particles.  All matter in the universe is composed of atoms, which are composed of the aforementioned subatomic particles.  The over one hundred known elements (kinds of atoms) all originate in stars, where extremely high energy collisions occur between atoms.  These collisions cause atoms to fuse together to form bigger ones in a nuclear process known as fusion. 

Ninety nine percent of the fusion reactions in stars involve hydrogen and helium.  But, if not for the remaining 1% of collisions, which fill in the periodic table, there would of course be no carbon, and then, no organic matter, and no life.  Life is an unlikely and bewildering occurence in so many ways.

Chemicals are combinations of atoms that have bonded together.  While there are only about one hundred known elements, there are millions of known chemicals, each with specific properties.

A person is an organism, which is composed of many systems, which are collections of organs, made up of tissues, which consist of cells.  The biological building blocks of a person are cells.  While cells are living matter, they are matter just the same; cells are made up of the atoms, whose origins lie not in the heavens, but in the stars.  What are we?  As the very famous astrophysicist, Neil deGrasse Tyson, likes to put it, "We are stardust."

The fact that man can observe the universe and question his origins with reason does set him apart from all other known life.  Although man is most certainly unique, his subatomic building blocks are the same as those for all matter, living and non-living.  As such, there is no reason to conclude that we are more than just bags of chemicals.

It is hard for one to accept that one is merely a walking collection of atoms.  We are often taught at a young age that we have some unobservable life force, or soul, deep within us.  I can accept the fact that I am a bag of chemicals, albeit with some discomfort, but I do have trouble dealing with one non-trivial implication that this notion leads to.

The laws of physics apply to all matter, whether it is living or not.  When a ball is thrown in the air, there is only one path it can follow.  When cells divide, they do so spontaneously, and like the ball, have no choice throughout the experience.  It is not so great a leap to say that an organism, like yourself, who is governed by the laws of physics, also makes no actual choices.

Wait a second.  I feel as though I make choices all of the time, in my brain.  I feel as though I make thousands of choices every day.  But my neural system is just a system, like my respiratory system.  Could it be that what feels like a choice is actually just the one possible consequence of any given scenario?  It is a hard concept to accept: as my building blocks are governed by physical laws, I have no free will.

I do not wish to embrace this philosophy, because of its implications.  It is however unscientific to discount a theory on the basis that its conclusions are unappealing.  Let’s continue down this scary rabbit hole for a moment then...

No free will means that there is no accountability for any actions.  This notion is freeing at first, as all of the anxiety I may feel over what feels like a choice disappears.  Contrastingly, a life devoid of actual choice represents a loss of identity.  As Neo of The Matrix exclaimed, “I don’t like the idea that I’m not in control of my life.”  Like Neo, I am perfectly happy to fuss over decisions, because it means that they are mine.

For those of you who want to believe that you are in control of your own destiny, let us seek solace in quantum physics, which says that all scientific outcomes are actually uncertain.  While the laws of the universe still apply, quantum physics says that the future state of a given system is only one of infinite possibilities.  In this case, all matter, including me, has an uncertain future.

I have always had distaste for quantum physics.  Classical physics empowers me with the ability to predict the future of a system with certainty.  But, if there is only one possible outcome for a given situation, then I am rendered powerless, as I am stripped of free will.  I cannot have it both ways, and must choose.

In physics, we may ignore quantum effects for bodies that are not too small (larger than atomic scale) and that do not move too fast (less than say 30,000 km/s).  As most scenarios in life agree with these conditions, we can ignore quantum physics for them, and take the simple classical approach.  The analogy for life is that most of our decisions are simplistic, and have just one reasonable solution. 

It is not that quantum physics is proven wrong in our day to day life; it is just not necessary to consider it most of the time.  It is for this reason that this modern branch of physics went unnoticed for so long.  Scientists needed to dig very deep to find it. 

When the universe has a non-trivial scenario to sort out, the effects of quantum physics are very noticeable.  Correspondingly, when a person makes a difficult decision, free will is invoked.

Where is the line drawn in the sand?  One particular cell has no free will, and I think that an ant does not either.  At some point, as a brain grows in size and complexity, the organism it is a part of is endowed with the ability to consider multiple options and choose one. 

As quantum physics is all about probabilities rather than certainties, and must be applied when dealing with phenomena at the sub-atomic scale, my justification for free will is as follows: "My building blocks, my cells, are composed of atoms, which are composed of sub-atomic particles; if these particles do not have a singular future, then neither do I.  If my future is not preordained, then it is possible for me to invoke free will."

It may turn out that sub-atomic particles are they themselves a manifestation of even smaller building blocks, known as strings.  If string theory were to be scientifically validated, we would know that the universe that we live in is even more chaotic than is currently believed, and have, in all likelihood, more reason to believe that our future is truly free.

What are we?  We are bags of chemicals with relatively uncertain futures.  I choose to believe that I do have free will.  And, although some decisions that I am confronted with are stressful, I am thankful for them, because they define who I am.