James Cronin passed away Aug. 25, 2016 at the age of 84. The famed particle physicist was awarded the 1980 Nobel Prize in Physics for his research that challenged the accepted theory of how matter behaved. A tireless champion of science, Cronin’s interests covered many fields in physics. From the Big Bang to cosmic rays, Cronin’s impact on science to present day is as expansive as the universe itself.
Cronin’s crowning achievement was his research with Val Fitch. In 1964, the duo were Princeton University professors experimenting with matter and its destructive opposite: antimatter. The work of Cronin and Fitch was an important step in validating the Big Bang theory for the creation of the universe.
The Big Bang Vs. the Steady State
Now widely supported in 2016, the Big Bang theory had its fair share of detractors at the time who believed in the Steady State theory for how the universe was created. Instead of an explosion leading to the birth of the universe, the Steady State theory suggested there was no beginning.
Both theories were trying to answer the origin of the universe while offering an explanation for its expansion. The Steady State theory, developed by Sir Fred Hoyle, Hermann Bondi and Thomas Gold, stated that matter was being consistently created at the same rate as the expansion of the universe in order to maintain the same density. The universe was persistent with no beginning, middle or end.
Imagine an expanding field of rubber ducks . Every time there is an empty space caused by the expansion, you replace it with another duck. That’s what was happening in the Steady State theory, except the ducks were galaxies and they were replaced by new galaxies from matter left behind.
Space-time diagram in the steady state theory. (Wikipedia Commons)
Using that same metaphor, picture the Big Bang as one giant rubber duck exploding to create an infinite number of of smaller rubber ducks and anti-rubber ducks. Some of these ducks would collide and destroy each other, but enough ducks would remain to seed the universe with matter to create stars, planets and galaxies.
Beyond bragging rights, confirmation or acceptance of an incorrect theory would severly limit scientific advancement. Think of it as going down a wrong path as you head to your friend’s house in an unfamiliar part of town. There are some things that make sense, but ultimately you went the wrong way and have to backtrack.
A Nobel-Winning Violation
Another battle between order and chaos was taking place in a much smaller, but no less significant, scale at the same time. Symmetry, the idea that the universe would be unaffected by reversing every particle’s charge (C), parity (P) or time (T), was the accepted standard when Cronin began his research.
Symmetry was slowly being chipped away, as the fundamental particles of the universe were beginning to reveal their chaotic nature. The Nobel Prize in Physics in 1957 was awarded to researchers who discovered a violation of P-symmetry. A violation of C-symmetry was previously discovered, which led to the theory that the two violations would cancel out, thus leading to CP invariance. Two wrongs would make symmetry right, according to this invariance principle.
In 1964, Cronin and Fitch found a CP-invariance violation through an experiment with a decaying kaon, a subatomic particle. Finding a CP violation also meant finding a T-symmetry violation because you wouldn’t end up with the same result if you reversed time. The CP violation revealed that matter and antimatter behaved differently, which helps explain why humans are around today.
If matter and antimatter were created in equal measure at the start of the Big Bang, they would have annihilated each other. Yet, there’s way more matter than antimatter in the universe. The CP violation, by explaining that matter and antimatter behaved differently, helped to provide a solution to why matter survived after the Big Bang, furthering the acceptance of the theory over the Steady State theory.
Cronin’s work served as a springboard to greater scientific discovery. Scientists could use Cronin’s work to probe deeper into fundamental particles and the universe itself. That expansion of scientific discovery was every bit as explosive as the beginning of the universe. All of science and industry can now put their collective energy into the Big Bang and this understanding of how the universe was formed.
Without a CP violation, we would still be facing many important questions about the Big Bang. More importantly, the CP violation led to incredible scientific theories exploring the existence of matter over antimatter and shaping multibillion-dollar scientific experiments.
The Large Hadron Collider
Through one violation, our understanding of the universe’s beginnings improved and the Standard Model of physics was clarified. Cronin’s work has paved the way for current experiments. CERN’s Large Hadron Collider beauty experiment continues to explore and measure CP violations in different subatomic particles.
Researchers around the world are still trying to figure out why there’s so much matter compared to antimatter as a direct result of the CP violation. Through this single observation, our understanding of physics and the universe has changed.
There’s still so much to learn about the very beginning of our universe. Think about all the celestial objects that needed to form after the Big Bang. Soon, NASA’s James Webb Space Telescope — being built by Northrop Grumman and scheduled to launch in 2021 — will be able to peer back in time into the deepest parts of the early universe to further unlock the mysteries of formation after the Big Bang.
Cronin’s scientific pursuits also involved cosmic rays, high-energy particles that constantly bombard Earth. Co-leading the Pierre Auger Project, Cronin’s efforts led to the Pierre Auger Observatory, an international scientific effort studying high-energy cosmic rays. Angela Olinto, the Homer J. Livingston Distinguished Service Professor in Astronomy and Astrophysics, said of Cronin in a statement, “He inspired us all to reach further into the unknown with deep intuition, solid scientific backing and poetic vision.”
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