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Saturday, September 25, 2021

Commemorating Niels Bohr

Great intellects always exist. However, it is far more seldom that those intellects extend far enough to shape history — far enough to execute and articulate logic to the degree that the rules of the game have to be re-written. For a great deal of time, the Earth was flat, and then human reasoning concluded that it was spherical. For another period, the Earth represented the center of the universe with the cosmos orbiting around it, and then human reasoning concluded that it is not. These shifts in thought were brought to light by observations made by the great intellects of their day.

One such intellect was a Danish physicist by the name of Niels Bohr, who if alive today, would have enjoyed his 127th birthday on Oct. 7. Unfortunately, he died in November of 1962.

Bohr, a young physicist at the University of Copenhagen in 1921, closely explored the works of some of his contemporaries, like Max Planck and Albert Einstein. Based on Einstein’s earlier research regarding the quantum nature of light energy and electrons, Bohr proposed a game-changing model for atomic structure. Bohr’s model of the atom won him a Nobel Prize in Physics in 1922, and to this day, serves as the accepted model for the structure of the atom.

“[Bohr] established the principles that allowed for the making of a periodic table…a success of quantum mechanics,” said Manuel Calderon de la Barca Sanchez, an associate professor of physics at UC Davis.

His model described electrons orbiting the nucleus of the atom at distinct energy levels, or orbitals. This means that the behavior of atoms can be quantified and predicted. Bohr’s work served as a conceptual foundation for modern chemistry, providing a set of rules that could be used to predict the nature and outcome of chemical interactions on the atomic level.

“[Bohr] explains the fundamentals of the nucleus which set a foundation for all of nuclear physics,” said Daniel Cebra, a physics professor at UC Davis.

After receiving his Nobel Prize, Bohr went on to found the Institute of Theoretical Physics in Copenhagen, which housed great minds like Werner Heisenberg, best known for his work on the uncertain nature of subatomic particles, known as the Heisenberg uncertainty principle.

“The position and the momentum of a particle cannot both be known at the same time, though either can be measured with as much accuracy as you desire,” said John Conway, a physics professor at UC Davis and an off-site researcher for the Large Hadron Collider at the European Center for Nuclear Research (CERN), which Bohr co-founded in 1954. “Quantum reality [is] a strange place indeed.”

Heisenberg was a great researcher and a close friend of Bohr. He was conscripted by the Third Reich to aid in Nazi Germany’s development of nuclear weapons. In 1941, Heisenberg called for a meeting with Bohr to discuss the implications of the project and the risks Bohr faced, being of Jewish descent.

According to Cebra, Heisenberg cautioned Bohr that if Bohr refused to aid in Germany’s nuclear program, he could face relocation to a concentration camp. Obviously, the meeting placed a huge stress on the friendship.

During the war years, Bohr used his status and estate in Copenhagen to protect and house Jewish refugee scientists from Germany. In 1943, during the Nazi occupation of Denmark, Bohr learned of his approaching arrest, and with the help of resistance forces, fled the country. Bohr took residence in Sweden and then England before leaving Europe for the United States.

Upon arriving in America, Bohr met with President Roosevelt to discuss the wartime potential of weaponized uranium. This audience played a pivotal role in the establishment of the Manhattan Project in Los Alamos, N.M., where Bohr acted as an advisor.

After the war, he truly believed that the U.S. and Britain should share their technology with Russia. In an open letter to the United Nations, he addressed that in an age of such dangerous technology, barriers to information would only serve to propagate fear and divide the world. For the sake of peace, Bohr called for openness and an increased level of human cooperation.

Despite his role in the creation of nuclear weapons, Bohr was one of the world’s first advocates for nuclear disarmament. He managed to meet with both Franklin D. Roosevelt and Winston Churchill in an effort to warn against the dangers of furthering nuclear research programs.

“Bohr was very concerned about a future nuclear arms race,” Conway said. “He pushed for the retention of civilian control over them in the U.S., which is still the situation today.”

On top of civilian control, Bohr argued for international regulation of nuclear weapons. His arguments led to the formation of the International Atomic Energy Agency (IAEA) under the United Nations.

In addition to playing a role in the foundation of the IAEA, co-founding CERN and creating a fundamental model for modern chemistry through his work in quantum mechanics, he was also the first-ever recipient of the Atoms for Peace Award, an award granted to individuals who develop peaceful applications for nuclear technology.

Throughout his life, Bohr sought to find elegant solutions to some of mankind’s great questions and divisive issues.

ALAN LIN can be reached at science@theaggie.org.

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