Quantum Mechanics and You

cat looking out of slit in a door

Why should anyone bother learning quantum theory? Quantum effects only take effect at tiny scales, after all. Life would be fine and dandy if we stuck to just the classical laws of physics. But to do so would be depriving ourselves of a unique perspective on life. The key difference between quantum mechanics and classical physics is the power of observation, transforming us from observers into meaningful players, intimately involved in the processes of the universe.

Origins of Quantum Theory

The scientific method remains to this day our best tool in the pursuit of knowledge; theories systematically and rigorously put to the test, and promptly discarded when they fail. Such a science-based approach led Isaac Newton to discover the ‘Laws of Motion’, able to describe an object falling from a tree, or even how the Earth went around the Sun. These laws would be known as ‘classical’ mechanics, able to describe all forms of matter.

Early in the 20th century, several (now famous) experiments were performed that probed the behavior of matter at the atomic level. The results went against the laws of classical mechanics, but the experiments were sound. Forced to discard what they knew about classical mechanics, scientists created an entirely new set of physical laws, dubbed ‘quantum’ mechanics. This new theory yielded extremely accurate predictions when it was put to the test, both on old and new experiments. Scientists were forced to accept it as a new reality.



Probability

As opposed to the concept of particles moving in set trajectories (that most of us can relate to), quantum objects are described using waves. These waves represent a series of ‘states’ in which the object can exist. Each state is assigned a probability, such that when the object is observed, it appears as a single, tangible particle with well-defined properties. The probabilities associated with each state are dynamic and can change with time or other external influence, but together they describe the behavior of the object in its entirety.

We can measure the distance between two atoms in H2, a diatomic molecule. States exist in which the two atoms are exceedingly close together, as well as infinitely far apart. Most states, however, will correspond to the atoms being a comfortable distance from each other, not too near and not too far away.

potential energy of dihydrogen bond
When we measure the bond distance between hydrogen atoms, we are most likely to find a length that corresponds to its ideal (lowest) energy. (Source)

The idea that simple probability determines behavior is not confined to small, sub-atomic particles. Because everything is made up of such sub-atomic particles with quantum properties, this phenomenon extends to macroscopic objects that we can see and touch as well. Quantum physics transforms the world we live in from a series of mechanical processes to one that is governed by probability alone.

Observation

Let’s say we do not actively measure the interatomic distance between two atoms; they are simultaneously in all positions at the same time, a la Schrodinger’s cat. A thought experiment by Einstein involves the ‘smearing’ of the position of the moon until an observer – in his case, a mouse – looks up and says ‘aha! it is right there’. And by this principle, the mouse, the planet, and indeed everything in the Universe would also consist of ‘smears’ of probabilities. While the entire notion of quantum mechanics relies on probability, it is the act of observation that provides us with tangible, empirical outcomes.

schrodingers cat quantum thought experiment
The famous Schrodinger’s cat thought experiment, in which a cat is placed in a box with a lethal toxin that is triggered after a random interval. Without opening the box ? and hence observing the state of the cat ? the animal is in a superposition of being both living and dead. The states converge into one of two outcomes only after the box is opened.

This is not the case with classical mechanics, in which the observer plays no part in the process. Objects move and go about their business governed solely by the universal laws of motion, oblivious to our presence. In quantum mechanics, the observers are very much intertwined with reality. While the mathematical descriptions of this claim warrant an entire area of research in itself, the philosophical implications of such a theory are just as profound.



Philosophical Implications

What Does it Mean to Observe?

What does it mean to observe, however? And perhaps more importantly, limited to our senses, what exactly are we observing? Empirical evidence forms the basis of knowledge and logical thinking. In the quantum world, acquiring empirical data must disturb, or perhaps even bring into existence, the values that we observe. This doesn’t mean that what we observe is necessarily incorrect, but that we cannot disentangle ourselves with the reality we experience.

Werner Heisenberg, one of the founding fathers of quantum mechanics, once said ‘what we observe is not nature in itself but nature exposed to our method of questioning’. Our senses can only tell us so much – who knows what other facets of reality exist beyond our comprehension? While the ‘true’ nature of reality – regardless of whether such a concept exists – remains hidden from us, it doesn’t make our observations any less valid.

To quote Neils Bohr, physicist and another pioneer of quantum theory: There is no quantum world. There is only an abstract quantum physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.

Determinism and Free Will

Newton’s laws of motion accurately described the physical properties of tangible objects, but in doing so, also transformed the universe into a deterministic one. Knowing the initial conditions, the past, present and future of every object can be calculated using these equations. Since nothing would be left to chance, our lives would be pre-determined, with the concept free will a mere illusion.

With the disconnect between mind and matter, this inevitably leads to some moral dilemmas. If everything about your life was set in stone at the beginning of the universe, can you really be held responsible for any of your actions? Remember that under classical mechanics, rational thought and moral values are unable to influence your actions.

Remember that thoughts we conjure in our brains are also subject to the processes of quantum mechanics. In this case, our choices are in states of superposition or ‘smearing’ until we consciously probe them, hence observing them and producing an outcome. Our own mental constructs a.k.a our thoughts and choices, are as much a reality as the one which we observe with our senses. These choices are free in that they are not pre-determined by the state of the universe, rather they are formed by the completely probability-based process of quantum mechanics!

Quantum Mechanics and You

Quantum mechanics provides us with a framework for turning our mental impetus into physical realities. As mentioned above, the act of observation is a fundamental principle of the quantum world. By observing a process, we reveal new insights that transcend existing values. Reality is as much constructed around us, as it is ourselves who give meaning to this reality!

The philosophical discussions arising from such a theory are extensive, and as such, continue to this day. ‘He does not play dice’, Albert Einstein famously wrote to Max Born in 1926. ‘He’ referring to Einstein’s concept of god, a collection of all the laws our universe is governed by. Einstein was very much a realist, with absolute belief in empirical methods and their results. The indeterminism and uncertainty surrounding quantum mechanics disturbed him greatly.

On the other hand, quantum mechanics, by being fundamentally indeterminate, lends meaning to our lives. The act of observation contributes to what we perceive as physical reality. Just by being mere observers, we are able to shape the very fabric of our Universe.



Reference

  1. Zeilinger, A. (1999). A foundational principle for quantum mechanics. Foundations of Physics29(4), 631-643.
  2. Stapp, H. P. (2017). Quantum theory and free will: How mental intentions translate into bodily actions. Springer International Publishing. https://doi.org/10.1007/978-3-319-58301-3

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