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
Physics differs from most of the other sciences because their practitioners tend to be divided into two groups.
Theoreticians solve problems by thought experiments often expressed through mathematical formulations as their primary tools. On the other hand, experimentalists design and carry out experiments to test hypotheses to see whether they hold up.
In my career in the neurological sciences, all the major names, among them several Nobel prize winners, were experimentalists. That was certainly true of the period in neurophysiology between 1930 and 1980.
Most of them achieved their results by recording electrical signals generated by cells and cell processes in the brain and/or spinal cord in response to various forms of sensory stimulation or associated with various movements.
The work was technically challenging and the successful ones were often as much engineers as physiologists, given that in the early days at least, they often had to build and maintain their own fragile equipment.
That was certainly true of the immediate post-Second World War period when money and resources were hard to come by and success required great patience, ingenuity and resourcefulness.
The studies by Hodgkin and Huxley on the nature of the electrical properties of nerve fibres are a case in point. They were beautiful, yet required all their considerable resourcefulness to make happen. They later earned a Nobel for their work.
But in the timeframe, we’ve been talking about in the NOTL library’s series on physics (1900 to 1930), when most of the major physicists – Boltzmann, Planck, Einstein, Bohr, Born, Heisenberg, Schrodinger, Pauli and Dirac – were theoreticians.
On the other side of the investigative coin, were the experimentalists epitomized by Marie and Pierre Curie, Rutherford and later Chadwick – who carried out experiments to confirm theoretical predictions of their own or those of others.
Three of the latter group stood out: first there was J.J. Thompson who discovered the electron in 1897, followed by Rutherford who discovered the proton in 1911 and later Chadwick, who discovered the neutron in 1932 – all discoveries based on solid experimental work.
Before them, were Henri Becquerel and the Curies, Marie and Pierre, the latter two who carried out the physically labour-intensive work that led to the discovery of the nature of radioactive elements and two new elements. For their work, the Curies and Becquerel shared a Nobel prize in 1903.
Later, in 1911, Marie Curie won a solo Nobel for her work on radium. Rutherford’s discovery of the proton would have been impossible without Marie’s radium, which provided the necessary alpha radiation (helium nuclei) with which he bombarded gold foil to find the neutron.
The two, experimentalists and theoreticians, sometimes eyed one another warily. This was especially so for Rutherford, who wasn’t keen about theoreticians, with one notable exception – Niels Bohr.
But the truth is the different disciplines needed one another. The experimentalists might never have sorted out the atom much beyond the nucleus. It was one thing to fire alpha particles at the nucleus and quite another matter to sort out the rules that governed orbiting electrons. The latter was the province of the theoretical physicists – Bohr, Heisenberg, de Broglie, Schrodinger, Born, Pauli and Dirac, armed as they were with great imagination and mathematical powers.
Bohr, for example, although not strong in mathematics, was bold in assuming that the orbiting electrons held to their fixed orbits because any other paths would cause them to lose energy and fall into the nucleus. And, moving a step further, he surmised that the energy released when electrons jumped from higher to lower orbits, generated the hitherto mysterious colours (wavelengths) emitted by different atoms – in the case of hydrogen – red, green and blue.
Those links took a brilliant mind – something Bohr had. His talent for creative solutions to challenging problems was equivalent to that of Einstein when he imagined that the energy emitted by the walls of a heated blackbody was similar to that associated with the energy emitted by gases, which are made up of atoms.
And so, like light, blackbody radiation was quantal in nature and, going further, so also was the entire electromagnetic spectrum and energy itself. As with Bohr, those links took a big mind to imagine.
To solve the mystery of the atom, it took both theoretical and experimental physicists to create plausible hypotheses and test them where possible, or sometimes it was the other way around – experimental observations came first as was the case with blackbody radiation and the photoelectric effect, followed by the theoretical basis for those observations. That’s how physics worked in those three decades and why that period was so productive.
Next week we take on the relative nature of time. In the meantime, remember to go to the library’s website to find a few short essays regarding entropy, time and the uncertainty principle. And if you tap on the YouTube icon at the bottom of the website pages you can access earlier programs.
Best wishes and hope to see you on Wednesday at 11 a.m. on Zoom.
* To view the health series, register through the library’s website, notlpubliclibrary.org.