Quantum mechanics: a bizarre theory

Since its inception in 1920s, quantum mechanics has puzzled the philosophically minded by its bizarre philosophical implications. That the debate as to the meaning of quantum mechanics is still going on is an indication of the fact that the dust raised over the world of science by this revolutionary theory of microscopic world at the beginning of the twentieth century is not yet settled. To make matters worse, the debate which was more or less settled for the majority of physicists –notably with the exception of Einstein and a few other big shots like Schrodinger and de Broglie– and was just a subject for the philosophy of science has been turning to the scientific circles as an increasing number of physicists are now undertaking to turn over the quantum stone for the last couple of decades.

This might not be as bad as it sounds. Because understanding quantum mechanics may very well hold answers to the deepest questions we face in physics and science today to unravel the mysteries of the universe. Some of these questions are: why existence? how to wed quantum theory to Einstein’s general relativity? The latter is the other grand and very successful physical theory about the universe. While quantum theory deals successfully with the tiniest of things such as the subatomic particles that are being studied in the much-vaunted Large Hadron Collider near Geneva; general relativity explains successfully what is going on at the other end of the size scale, that is, the largest objects such as black holes and supernovae. Nevertheless, they are two exclusive theories at the moment. And since we don’t expect any artificial dividing size barrier in the universe, the two theories must somehow be blended seamlessly into each other to form a “theory of everything,” which has eluded some of the most brilliant minds so far.

Making no mistake regarding what quantum mechanics has done for us

Beset by unsettled debates and ongoing scientific research on its foundations, quantum mechanics might sound “not so solid” or even not a useful theory at that. However, let me remind you of the fact that it has been accepted without any exception that quantum mechanics has been the most successful scientific theory mankind has ever came up with to understand nature. This is not without good reasons. If one looks around us, it is rife with the fruits of quantum mechanics: semiconductors, transistor radios, computers, cell phones, lasers, magnetic resonance imaging (MRI) etc. Simply put, the technology we have around us today would be impossible, had it not been for the success of quantum physics.

So, what is the problem?

If quantum mechanics has provided so much benefit for mankind, why is all that ado?

The problem is that, all this success is based on the concepts of probability, uncertainty, and philosophically uncanny implications. To give a simple example, quantum mechanics will never be able to tell us when exactly a plutonium atom will decay. All it can say is to give you a probability with which a radioactive atom might decay. Consequently, quantum mechanics claims that the state of a plutonium atom is a mixture of two possible states: decayed and inert. It is not one or the other, contrary to our classical intuitions. Whether it is one or the other, it cannot be known unless one makes an observation by performing a measurement on the system. If there is no measurement done on the system, says quantum mechanics, then the state of the system is a blend of the two possibilities. In other words, the atom does not take a “reality stance” until a measurement is made on it.

To translate this “absurdity” into our classical intuition, Schrodinger has come up with a gedanken (thought) experiment. Suppose one puts a cat in a box with a glass bottle of deadly poison, where an hammer is sitting right above the bottle, and the hammer in turn is hooked up to a Geiger counter. The setup is such that the hammer will break the bottle only when the Geiger counter is triggered. The bottle has a very tiny amount of a radioactive atom inside that may or may not decay within the next hour (both with fifty percent probability). Now, after one hour of waiting, what will be the situation of the cat inside? Naturally, one cannot know if one does not open the box. But what if one is to make a guess? We, with our classical expectations, would say that the cat is either dead or alive. How about the answer of quantum mechanics? Quantum mechanics says before we make any measurement (such as opening the box), the cat is in a mixture state of being dead and alive at the same time. In other words, the cat –like the atom above– does not take a “reality stance” until a measurement is made on it. Until then it has a “ghostly” existence. The absurdity of this statement is clear to all of us. It is one of the paradoxes that quantum mechanics has brought with itself.

In fact it was none other than Einstein himself, one of the greatest physicists of all time, who has spearheaded the opposition to the bizarre implications of quantum theory as it relates to the objective reality. But he had not thought that quantum mechanics was wrong, he rather opposed it because he thought the theory, as we know it today, must be incomplete. However, not everybody was bothered with the eerie consequences of quantum mechanics. In fact, the majority of physicists embraced the quantum theory without any deep doubts about it. This is certainly due to the enormous success of the theory as mentioned earlier.

Therefore, one should make no mistake about the mathematical soundness of quantum theory. In addition, as mentioned at the outset, most physicists do not share the concern related to the objective reality. They simply accept it

Interpretations of quantum mechanics

Due to the lack of a complete understanding (or acceptance thereof), and/or philosophical satisfaction of the meaning of quantum mechanics, there appeared a host of schools of thought from the beginning regarding the bizarre nature of quantum theory. There are three main schools of thought: the realist, the orthodox, and the agnostic. The realist school has been advocated by Einstein. He simply asserted that the indeterminacy is not a product of nature but is due to the incompleteness of quantum mechanics.

The orthodox camp has Neils Bohr as its patriarch, and their “exegesis” of quantum theory is formally known as the Copenhagen interpretation. This school embraces the bizarreness of the theory as a given. In fact, Schrodinger –who like Einstein had problems with the theory as it stood– came up with his “cat” thought experiment to point out the weirdness of the way Bohr and his followers were viewing the quantum. Notwithstanding its “out-of-this-world” implications, it is the Copenhagen interpretation that has become the “standard” interpretation of quantum mechanics.

Bohr’s position in this regard cannot be better expressed than with a dictum the eminent physicist John. A. Wheeler has formulated: “no elementary phenomenon is a phenomenon until it is a registered (observed) phenomenon.” It is basically saying that in the atomic world “the moon is not there when nobody looks,” playing on the title of one of David Mermin’s articles on the subject. This is the most bizarre feature of quantum mechanics and is called observer participancy. In other words, you and I, and the detectors in a lab are eerily connected to what transpires in the universe. In fact, Wheeler called our universe a self-excited universe, meaning that the universe is given meaning by the "observers" it creates.

Finally, the agnostics posit that one should not bother with things one will never know, and hence there is not much left for discussion.

Although, any scientifically “serious” interpretation would fall under one of the above three general categories, there are many specific interpretations of quantum mechanics out there that people talk about. How will one know which interpretation is the correct one? By using that age-old scientific criterion: whichever one provides a successfully measurable experimental scheme! Without such a proposal, they will continue to be only one of many “interpretations” of quantum mechanics.

Serkan Zorba