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Steven Cowley, PPPL director, explains “the Magnetic Universe” at Science on Saturday

Steven Cowley, director of the Princeton Plasma Physics Laboratory (PPPL), has spent a lifetime working to develop fusion energy as a viable source of electricity. But in his spare time, he enjoys investigating the role of magnetism in the universe.   

“I’m a fusion nut and I spent most of my career talking about how to make fusion work,” Cowley told the audience at PPPL’s second Ronald E. Hatcher Science on Saturday lecture on “The Magnetic Universe” at PPPL on Jan. 19. “I’ve also done some work understanding magnetic field lines in the universe. It’s kind of a hobby.” 

Cowley is a theoretical physicist and international authority on nuclear fusion and astrophysical plasmas. The director of PPPL since July 2018, he  received his Ph.D. in astrophysical sciences from Princeton University. Prior to coming to PPPL, he was president of Corpus Christi College, Oxford, in the United Kingdom. He previously headed the EURATOM/CCFE Fusion Association and was chief executive officer of the United Kingdom Atomic Energy Authority (UKAEA). Cowley was knighted by Queen Elizabeth in October 2018, for his services to science and his contributions to the development of nuclear fusion. 

Cowley explained that to understand how magnetic field lines move, you have to understand plasma, an electrically-charged gas that makes up most of the visible universe. The charged particles are caught in a spiral along the magnetic field lines and this allows scientists to use magnets to control the plasma. 

Scientists are researching how magnetic fields were formed in the universe or “magnetogenesis.” Cowley joked that the name “sounds like a superhero or at least a superhero film.” It is a fascinating question and exploring that question and others surrounding the behavior of magnetic lines in the universe is also part of his “hobby,” Cowley said. 

Holding the plasma together in the galaxy

Magnetic fields are the glue that holds the plasma together in the universe, Cowley said. “It’s an invisible force in space. It pushes in a particular direction.” With the help of Arturo Dominguez, senior science education program leader, Cowley demonstrated a way to “see” magnetic field lines.  He showed how a bar magnet placed on a clear rectangle of plastic containing hundreds of tiny iron filings that  line up along the magnetic field lines.   

Cowley explained that the Earth itself is magnetized with the Earth’s North geomagnetic pole located in Greenland and migrating toward Russia. He used a small compass to show the audience how a compass can trace a magnetic field line by following it north at every step. 

Earth’s Sun is made of plasma and magnetic loops from the Sun are responsible for the beautiful coronas that bubble from its surface. Cowley noted that the  energy released by the Sun’s eruptions are billions of  times larger than a nuclear bomb. When some of the energized particles from the sun reach the Earth, we observe the interaction as the phenomenon we call the Northern Lights. Cowley and Dominguez demonstrated this with the Planeterrella, a glass bell jar with two spheres representing the Earth and the Sun that simulates the phenomenon.   

Early influences 

Cowley discussed the early influences that made him a scientist. He recalled he first became excited about science when his father, who was a faculty member at the University of Cambridge, was doing a sabbatical at MIT. His father was very enthusiastic about his research into a magnetic fluid. When Cowley asked what it could be used for, his dad jokingly replied that the fluid could be used “to help spacemen drink their beer,” and that got the young Cowley hooked, Cowley said. Cowley also said he was inspired by Shaun Wylie, a mathematics and Greek teacher at Cambridgeshire High School for Boys (now the Hills Road Sixth Form College) in Cambridge. It was only later, Cowley said, that he learned Wylie had been one of the codebreakers responsible for cracking the Enigma Code during World War II. 

If you missed Cowley’s lecture, an archived version will soon be available here

Science on Saturday lectures will continue through March. The Feb. 9 lecture will feature Juliane Gross, of Rutgers University, discussing “Planetary Science at the Coldest Place on Earth: The Antarctic Search for Meteorites.” 

Come to the lectures early for coffee and bagels and to find the best seats in PPPL’s MBG Auditorium. Overflow seating is available in the cafeteria. 

A full schedule of the lecture series is available here. Adult visitors must show an official ID. If you are not able to make it to the lecture, you can watch it live here. If a lecture is canceled due to inclement weather, a message will be left on the Science on Saturday Hotline at 609-243-2121. 

PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.


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Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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