Dr. William Brown is a professor of neurology at McMaster University and co-founder of the Infohealth series held on the second Wednesday of each month at the Niagara-on-the-Lake Public Library.  

Dr. William Brown

Special to The Lake Report

In this, the third in the library’s series, “The Camelot Period in Physics: 1900-1930,” we move on to the quantal nature of universe writ tiny – the atomic and subatomic levels.

That’s quite a shift in gears given that the first two sessions focused on those scientists in the early 1900s who revealed that the universe was far larger than was previously thought, and moreover was expanding, evidence for which led to the Big Bang hypothesis and a compelling narrative for the evolution of the universe.

At the beginning of the 20th century the very existence of the atom was questioned by some of the best physicists of the day, including at the top of the heap, Max Planck.

And any notion that light, never mind the rest of the electromagnetic spectrum, or for that matter, energy, might be composed of particles, came as a unwelcome challenge to a generation of physicists brought up on Faraday’s and Maxwell’s studies of electromagnetism in the 1800s and a large body of evidence attesting to the waveform nature of light.

But there was a paradox at the heart of physics and no one got to the heart of the matter better than Albert Einstein. In his 1905 paper on the quantal nature of light, for which work he later won the Nobel prize, he put the dilemma this way.

“There exists a profound formal difference between the theories that physicists have formed about gases and other ponderable bodies (particles), and Maxwell’s theory of electromagnetic processes in so-called empty space. While we consider the state of a body to be completely determined by the positions and velocities of a very large, yet finite, number of atoms and electrons, we make use of continuous spatial functions to describe the electromagnetic state of a given volume.”

Therein lay ‘the great distinction between theories based on particles such as the kinetic theory of gases and seemingly at odds theories that involve continuous functions like the electromagnetic fields of the wave theory of light” (Kumar, 2010). It was a distinction Einstein would deal with in his paper on the quantal nature of light – one of four revolutionary papers he published in 1905.

That paper on the quantal nature of light concluded, based on Einstein’s analysis of Philipp Lenard’s observations of the photoelectric effect, that the observations were inconsistent with the wave form theory of light, but made sense if light was thought of as packaged in discrete quanta – what later would be called photons.

Einstein went on to take a fresh look at Planck’s analysis of blackbody radiation in 1900 in which he reluctantly resorted to accepting the quantal nature of radiation as a contrivance to make sense of his equations.

Einstein showed no such reluctance – light was quantal – but rather than using Planck’s tortured logic, Einstein based his conclusions on his analysis of the photoelectric effect and the nature of gases and energy.

Summarizing Planck’s work, he wrote, “Mr. Planck’s determination of the elementary quanta is to some extent independent of his theory of blackbody radiation.” Einstein’s paper on the photoelectric effect (and blackbody radiation) was quite the start for the young brash Einstein still working in a patent office in 1905.

His audacity, brashness and energy for his work is caught in a letter he wrote to his best friend, Conrad Habicht.

After teasing Habicht for not writing, Einstein went on to say, “I promise you four papers …. The first deals with radiation and energy properties of light and is very revolutionary …. The second paper is a determination of the true sizes of atoms… The third proves that bodies on the order of magnitude of 1/1000 mm, suspended in liquids, must already perform an observable random motion that is produced by thermal motion. Such movement of suspended bodies has actually been observed by physiologists who call it Brownian molecular motion. The fourth paper is only a rough draft at his point, and is on electrodynamics of moving bodies, which employs a modification of the theory of space and time.”

Later there was a three-page add-on, which contained that most iconic of equations, E=mc2, or energy (E) equals mass (m) times the speed of light squared. Wow.

Taken together, Einstein’s body of work for 1905 constituted his annus mirabilis. In his achievement, he ranks with Isaac Newton, who in 1666, tucked away in his mother’s countryside home to escape the plague, had his own annus mirabilis when he developed calculus, an analysis of the light spectrum and the laws of gravity. Quite an achievement by any measure, as was Einstein’s 239 years later.

The “quantum” was a huge step forward in physics and was engineered by the two reluctant fathers of quantum physics, Planck and Einstein, two men who could not have differed more in nature, dress, habit and their understanding of physics and yet became close friends. That’s an important lesson that applies to life anywhere in anytime.