Contemporary Age - Quantum Mechanics (20th century)

The study of how we know reality, epistemology, has been a fundamental guiding thread in the history of philosophy. The 20th century introduced quantum mechanics: a revolution in natural philosophy's vision of reality.

In 1900 Max Planck, a German physicist, working with the new light bulbs invented by Edison, noticed that the color of the light changed as the filament of the light bulb heated up, but only to a point. It turned white but did not continue until blue or ultraviolet. He could not explain the relationship between the temperature of the filaments and the color of the light it produced and called it the "ultraviolet catastrophe".

In 1905, Albert Einstein proposed a theory to explain Planck's dilemma and at the same time another inexplicable connection between lights and electricity: the "photoelectric effect".

Einstein argued that we had to forget the idea that light is a wave and think of it as a stream of small bullet-like particles. The term he used to describe a particle of light was ‘quantum’. For Einstein it was a small point of energy and the light was made up of small particles or quanta. The prevailing physical opinion at the time was that light was a wave, more precisely an oscillation of the electromagnetic field. This dual nature of light, corpuscular and undulating was unlike anything seen before.

Physics relies on experimentation for its advancement, and confirmation of the double state of electrons came in the mid-1920s when an experiment was conducted at Bell Laboratories in New Jersey, USA. They fired a beam of electrons from an electron gun onto a screen with two slots for electrons to pass through. The slots then hit another screen at the back. Scientists discovered that, on a micro scale, physical objects have a dual nature: depending on the circumstances, they can behave as a set of particles or as a wave. The standard interpretation tells us that the electron is launched and collected as a particle, but it propagates as a wave. However, the theoretical explanation did not unravel the mechanisms of this phenomenon.

In 1927, Heisenberg and Bohr presented the so-called Copenhagen interpretation of this problem, proposing that wave equations described where entities like electrons might be, but that entities did not actually exist as particles until someone searched for them. The act of observation caused their existence. In Bohr's own words, the entities in question had no "independent reality in the ordinary physical sense". This state of existence, in all possible states at once, was called a coherent superposition: the total of all possible states in which an object can exist. When we look at an object, the overlay collapses and the object is forced into one of the states of its wave function. The Copenhagen interpretation was theoretically tested in a famous thought experiment (a natural philosophy reflection) about a cat in a box: Schrödinger's cat (1935).

The new quantum mechanics imposed two fundamental philosophical restrictions on the theory of knowledge: 1. we can only know the probability of finding a particle in a given place; 2. the observer interacts with what is being observed. As a consequence, the determinism of classical physics is considered an approximation to a reality where the notion of total knowledge seems impossible. Since then the goal of any metaphysical interpretation of quantum mechanics is to account for these epistemological violations.

Einstein was very skeptical of the new explanation. He believed that, although much had been accomplished, the mechanisms of the theory still needed to be understood. He discarded the idea that nature was governed by chance at its most fundamental level stating:

"God does not play dice with the universe". Einstein

For him the probabilistic description of the natural world could not be the last word. There had to be an objective reality, independent of the observer. Quantum mechanics, useful as it was, had to be an incomplete theory. He believed in a deeper level of physical reality where the normality of classical physics existed: determinism and the separation of the observer and the observed.

Niels Bohr, on the other hand, saw quantum mechanics as an expression of the world of the very small. For him, there was no reason why the rules of classical physics should also apply in such a different probabilistic and microscopic domain.

In 1949 Bohr published Discussions with Einstein on Epistemological Problems in Atomic Physics. Here we find the traditional development of philosophical discussion: thesis against antithesis. Bohr's vision was random and microscopic; Einstein's was deterministic and macroscopic. They discussed their respective theses for years.

Behind the Einstein-Bohr debate are opposing beliefs about physics and, more than that, about the nature of ultimate reality. Theirs was a "religious war" fueled by two very different ways of thinking about Nature and our relationship with it.

After the Second World War, the pragmatic decision was made to apply the ideas of quantum theory and stop worrying about the philosophical side. This led to a deep understanding of semiconductors, which helped create the modern electronic age that produced lasers, revolutionizing communications, new medical advances, and advances in nuclear energy. The metaphysical debate about the reality of the quantum world was simply hidden under the rug.

In the early 1960s, John Bell designed an experiment to rule out Einstein and others' theory that quantum physics is incomplete as an explanation. He experimentally proved that the only way hidden variables could explain quantum physics predictions is if they are "nonlocal", somehow associated, and capable of instantaneously influencing each other, no matter how far apart they are. Bell reduced this idea to a single mathematical equation, published in 1964.

However, there is still no complete theoretical explanation for the strange results of quantum mechanics.

More information:

Max Planck (1858 - 1947)
Albert Einstein (1879 - 1955)
Niels Bohr (1885 - 1962)
Werner Heisenberg (1901 -1976)
Erwin Schrödinger (1887 - 1961)
John Bell (1928 -1990)

No comments:

Post a comment