In Honor of P.A.M. Dirac, A Founder of Quantum Theory
It is possible that nature produces beings of otherworldly intelligence from time to time, supreme minds that show up every hundreds or even thousands of years. As a university student, I am exposed to brilliant instructors, to uncanny students… people that deserve utmost respect and admiration. However, there are levels of intelligence that are down-right frightening. As a biology student, I do not consider biology or chemistry the most powerful sciences; rather, I consider physics the top science and theoretical physicists to be science’s top dogs. Here, I will try to pay tribute to one of the greatest minds that have ever lived. It is not Isaac Newton or Albert Einstein, but someone at the same level: the British theoretical physicist, Paul Adrien Maurice Dirac.
Paul Dirac was born on August 08, 1902 and passed away rather recently, on October 20, 1984. Let’s start with what he accomplished. Paul Dirac was Great Britain’s intellectual representation during the revelation and revolution of quantum mechanics. It is sad that many people do not care about quantum mechanics, primarily due to ignorance, but quantum mechanics and special relativity is what makes our world the way it is today, technology wise. Quantum mechanics is the study of mechanical system whose dimensions are at an atomic scale, such as molecules, atoms, electrons, protons and other subatomic particles. Unlike people in these modern times, knowledge of the existence of atoms and their laws were not known at the turn of the late 1800s to the 1900s. Max Planck started it all while studying black body radiation, and Einstein followed, explaining the photoelectric effect. I can explain these theories at depth some other time, because the point here is to tell you about Dirac.
The birth of quantum mechanics ushered in some of the greatest minds to work on the mathematical foundations of this new theory. Let us take a minute to review the players. The country that started it all was Germany, and as such, it supplied gifted players. Max Planck, Albert Einstein, Max Born, and Werner Heisenberg represented Germany. Wolfgang Pauli and Erwin Schrödinger represented Austria. France supplied Louis de Broglie. Niels Bohr hailed from Denmark (and trust me, he was representation enough). Many others also contributed to quantum mechanics, but these I mention are the true fathers of the theory. Each one of them was more than a mere genius. They were the cutting edge of our frontal lobe.
From June 1925- June 1926, three complete versions of quantum theory were formulated: Heisenberg’s Matrix Mechanics, Schrödinger’s Wave Mechanics, and Dirac’s version, using quantum algebra or Dirac algebra. Though they were formulated, they were not properly understood. Heisenberg needed Pauli, Born, and a Pascual Jordan to help him interpret his version. With it, you could derive the spectrum of hydrogen and additional lines produced by electric and magnetic fields. Pauli showed Matrix Mechanics was correct, but the thing was, it was all numbers, there were no pretty pictures for one to see, like Bohr’s atom model. The difficult mathematics and the lack of a picture was extremely unpopular with the other great physicists. Particularly distressed was Erwin Schrödinger, a polymath and a lover (he was a notorious womanizer). Schrödinger was very moved by de Broglie’s idea that light particles may exhibit wave-like properties, in other words, light is both a particle and a wave, a duality, and all matter could also posses this characteristic. He set about to make a picture of the electron wave, as it travels in time on one of the Bohr orbits. The Schrödinger equation is an equation that describes how the quantum state of a physical system changes in time. Or, more generally, it is an equation which can be applied to any physical system, in which the mathematical form of energy is known. Schrödinger’s equation can describe atomic and subatomic systems, electrons and atoms and even large systems, like the universe.
Schrödinger’s wave equation has been hailed as one of the epitomes of 20th century thought, and eclipsed the abstract matrix mechanics. Physicists found it more appealing than Heisenberg’s model because the math was less difficult and provided a picture of atomic behavior with vibrating waves. Schrödinger and later, more elegantly, Paul Dirac showed both wave mechanics and matrix mechanics to be mathematically equivalent. Wave mechanics was here to stay. In 1930, at the tender age of 28, Paul Dirac published The Principles of Quantum Mechanics, arguably the best physics book since Newton’s Principia. In this book, he not only shows that Matrix Mechanics and Wave Mechanics are mathematical equivalent, but goes on and derives the beautiful Dirac Equation. This relativistic wave equation is even better than Schrodinger’s because it fuses special relativity and quantum mechanics to explain the behavior of elementary particles like electrons and other fermions. One of the most astonishing aspects of this equation is that it demands the existence of antiparticles (antimatter) and matter-antimatter annihilation. The electron, for example, has its anti-electron, an electron with a positive charge, which Dirac found in a sea of negativities. Dirac’s anti-electron was experimentally confirmed 2 years later, in 1932, by American physicist Carl D. Anderson at Caltech, and was named the positron. The ‘P’ in PET scan stands for positron, so we can easily link the importance this had in the world. The first existence of antimatter was thus, confirmed. Paul Dirac also started quantum electrodynamics (QED), which set the stage for Richard P. Feynman, Julian Schwinger, and Shinichiro Tomonaga to further develop. For all these reasons aforementioned, Paul Dirac won the 1933 Nobel Prize for Physics (which he shared with Schrödinger). Legendary!
Let us now investigate Paul Dirac, the person. He was born in Bristol, England. His father was a strict and authoritarian French teacher and apparently his early childhood was not a happy one. He completed a degree in electrical engineering fro the University of Bristol. He later received a bachelor’s degree in mathematics. In 1923, he gained a grant to conduct research at St. John’s College, Cambridge, under Ralph Fowler. When the talented Werner Heisenberg lectured at Cambridge over his theory of matrix mechanics in 1926, Fowler simply passed one of Heisenberg’s manuscripts to Dirac, with the instruction, “See what you think of this.” Dirac worked on them religiously. He was able to deduce Matrix Mechanics and was given a PhD by Cambridge. Dirac quickly became a member of the elite fathers of quantum mechanics with his subsequent work, and travelled to the major centers of quantum mechanics development, Gottingen, Munich, Berlin, and Copenhagen. Dirac was famous for being quiet. This is actually one of the reasons why he is not known well outside physics. His character differed from the other major physicists in that he was a recluse. He was also an atheist, in a Solvay conference he remarked:
“I cannot understand why we idle discussing religion. If we are honest—and as scientists honesty is our precise duty—we cannot help but admit that any religion is a pack of false statements, deprived of any real foundation. The very idea of God is a product of human imagination…. I do not recognize any religious myth, at least because they contradict one another…”
At one time he stated, “God used beautiful mathematics in creating the world.” And one time while he was eating at a table, someone remarked that it was windy. Dirac stopped, got up, went to the door, came back, sat down, and said, “Yes, it is windy.” Even the great Danish physicist Niels Bohr could not escape Dirac’s nature. When Bohr was writing an article for publication in front of Dirac, he blurted out that he did not know how to finish a sentence. To this Dirac replied, “I was taught in school never to start a sentence without knowing the end of it.” Pretty hilarious because he was not being mean, he was simply Dirac. There are many other quotes that I invite you to search for that can shed light on the personality of this great man. Dirac became Lucasian Professor of Mathematics at Cambridge from 1932 to 1969, this position is currently held by Stephen Hawking and was held by Isaac Newton a long time ago. He married physicist Eugene Wigner’s sister, Margit, in 1937. He adopted Margit’s two children, Judith and Gabriel. Paul and Margit Dirac had two children together, both daughters, Mary Elizabeth and Florence Monica. In the last 10 years of his life, Paul Dirac relocated to Florida to be near his daughter, Mary Elizabeth. He worked at Florida State University in Tallahassee, Florida and passed away in October 20, 1984. One of Dirac’s student, John Polkinghorne, a prominent British physicist, remembers that Dirac “was once asked what was his fundamental belief. He strode to a blackboard and wrote that the laws of nature should be expressed in beautiful equations.”
