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The Annual Report of the College of Letters & Science

Unlocking a Secret of the Universe

Many small gifts to the L&S Annual Fund may help solve an ancient puzzle of cosmology

In the cosmos, all celestial objects — planets, stars, galaxies and clusters of galaxies — have magnetic fields. The magnetic field of our home planet is most easily observed in the fact that the needle of a compass points north.

But the origin of magnetic fields in the universe — including Earth’s — remains a puzzle of cosmology, despite many determined efforts by scientists to ferret out the secrets of how they first arose.

Now scientists in the College of Letters & Science are taking their turn at solving that puzzle. The Madison Plasma Dynamo Experiment, directed by Physics Professor Cary Forest and Astronomy Professor Ellen Zweibel, studies how magnetic fields are generated by replicating the process by which they are
created — right on campus.

This ground-breaking research is funded by a $2.4 million grant from the National Science Foundation and leveraged by many small gifts from alumni and donors to the L&S Annual Fund. That backing allowed for the construction of a new, state-of-the-art laboratory to house the space-age-looking sphere that is the centerpiece of the experiment.

The hollow aluminum sphere, three meters in diameter, heats gas to 500,000 degrees Fahrenheit. At that searing temperature, the 10,000-pound sphere turns gases into plasmas: superheated gases in which atoms have been stripped of their electrons, like those in space. From there, the plasma is stirred using magnets and then, in the words of Forest, “we make a turbulent mess of flows” that creates magnetic fields.

The end result is the simulation of cosmic dynamos, which had not been done in a lab before the UW-Madison team accomplished the feat in January. Stars, including our own sun, and planets have dynamos — the Earth’s dynamo generates the magnetic field that shields us from solar winds — as do galaxies and clusters of galaxies.

The aluminum sphere has strong ties to the state of Wisconsin. Core pieces of equipment were manufactured by Wisconsin companies and tested without leaving the state. Chosen after a nationwide search, Portage Casting & Mold in Portage cast the sphere itself, and three other Wisconsin companies fine-tuned it. Milwaukee’s Lafayette Testing Services ensured that the cast was free of holes using X-ray analysis; Luxemburg’s D&S Machine Service sized the two halves before they were attached; and Beloit’s Metallic Bonds adhered to the sphere’s interior an alumina coat capable of handling scorching temperatures.

“We are particularly proud of this aspect of the project,” Forest says. “That, after a national search, we found we could do this in our back yard — with Wisconsin companies and local expertise — is exciting.”

— Terry Devitt contributed to this story

Workers at Portage Casting and Mold pour more than 7,000 pounds of molten aluminum into a five-section mold for half of the sphere for the Madison Plasma Dynamo Experiment.

Workers at Portage Casting and Mold pour more than 7,000 pounds of molten aluminum into a five-section mold for half of the sphere for the Madison Plasma Dynamo Experiment. (Jeff Miller, University Communications)