The Simons Center Della Pietra Family Auditorium welcomed Swedish physicist Mats Larsson to discuss the historical buildup and lasting impact of the Dirac equation in physics and medicine on Nov. 22.

Larsson, the chair of the Nobel Prize committee for physics, described why the Nobel Prize committee gave English physicist Paul Dirac the award in 1933. 

“In that era, the new quantum mechanics was not easy to digest. The Nobel committee felt his discovery was easy to understand, was practical, and the publications were very clear. So he had very strong nominations,” Larsson said.

In 1928, Dirac discovered the positron or the “antielectron” — a subatomic particle — by relating his wave equation to Albert Einstein’s theory of special relativity. Dirac’s wave equation discovered that positrons have the same mass but the opposite charge of an electron. In modern medicine, these particles are observed through radiography to detect cerebral, neurological and cardiological diseases. 

Known as positron emission tomography (PET), these scans are a nuclear imaging technique based on the metabolic activity within the body. PET scans pinpoint which parts of the brain propagate signs of cancer or tumors. Since the brain is 73% water, which is electrically conductive, PET detects the positrons in the human brain, which helps radiologists diagnose patients.

The Dirac equation was a “breakthrough for physics,” according to Dmitri Kharzeev, a professor of nuclear and particle physics at Stony Brook University who attended the lecture. PET is one of the many outcomes that have derived from Dirac’s relativistic wave equation. 

“One of the important discoveries made at the Brookhaven National Lab was the perfect fluid behavior of water plasma,” he said. 

Water — which has three states, liquid, solid and gas — is being observed in a fourth plasma state at Brookhaven National Lab. Since water is a polar molecule with uneven charge, the Dirac equation is used to understand how vortical fluid works in super-cell tornado cores and Jupiter’s Great Red Spot, according to Kharzeev.

Application of Dirac’s wave equation to the physical world can also be viewed through the Relativistic Heavy Ion Collider (RHIC), according to Alexander Abanov, a physics and astronomy professor at Stony Brook who attended the lecture. Particle accelerators help scientists observe atoms and other small particles to better understand the universe. 

“They wouldn’t be here without the Dirac equation,” Abanov said.“The goal of physics is to understand how the universe works, and this equation is the most exciting aspect.” 

In the 86 years that the Dirac equation has been used, “science has advanced so much,” he added. 

Another attendee who was intrigued by the lecture was Sara Kurdi, a sophomore physics major. 

“I wanted to see what the future is for the Nobel Prize in physics,” she said. “Physics is a rapidly evolving field. My physics professor, [Tom] Hemmick, got me interested in physics research.”

The role of the Dirac equation in physics can be expanded into fields outside of chemistry and medicine. For instance, one audience member asked about the application of Dirac’s wave equation in astronomy. 

Benjamin Shevah, a junior physics major who attended the lecture, said he wants to “understand outer space.” 

“We know space is constantly expanding,” he said. “But I want to be the one to tell you why.” 

Shevah added that he wanted to gain a better understanding on why Dirac and Einstein “come up in my classes all the time. I didn’t know why but I do now.” 

Abanov said that the Dirac equation has become a mainstay in the constantly evolving field of physics. 

“There have been corrections in other equations, but Dirac’s still stands today,” Abanov said. “Everything we know about the most fundamental interactions in the world are thanks to the Dirac equation.”

The Provost lecture series can “help promote the sciences and strengthen their influence in society,” Larsson said. By implementing the Dirac equation into broader fields such as medicine and chemistry, Larsson believes young physicists are the future, and could explore our world and the extraterrestrial one too.