No. 3059: VERA RUBIN AND DARK MATTER

by Andy Boyd

Click here for audio of Episode 3059

Today, that which can’t be seen. The University of Houston presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

In 1950, at the age of only twenty-two, Vera Rubin stood before an audience at a meeting of the American Astronomical Society. Rubin had an interesting idea. Planets revolved around stars. Stars revolved around the center of galaxies. Maybe the galaxies were revolving around the center of the universe.

She presented her results and waited for questions. The crowd was skeptical. The work was respectable, but far from conclusive. The idea of a spinning universe never did gather steam. But many years later Rubin would turn her attention to the spinning of the galaxies themselves, and in doing so would discover key evidence for one of the strangest theories in the history of science.

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Astronomer Vera Rubin at her “measuring engine” used to examine photographic plates, 1974. Photo Credit: Carnegie Science

But before she could reach that point, Rubin would have to navigate the cultural norms of the 1950s. She finished her master’s degree at Cornell then followed her husband to his job in Washington. By Rubin’s own account, her husband was supportive and encouraged her to continue her studies. At first, she demurred, choosing to stay at home with their newborn child. But following a phone call from an eminent cosmologist, she returned to finish her Ph.D. at Georgetown while pregnant with the couple’s second child. Rubin was able to teach at Georgetown for many years, but never had the opportunity to do observational work with telescopes. That would have to wait until the couple’s fourth child was out of diapers. But the wait had its rewards. By the time she was ready, Rubin received an invitation to become the first woman to observe at the famous Mount Palomar observatory.

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In 1965, Carnegie scientist Vera Rubin was performing space observations at Lowell Observatory in Flagstaff, Arizona, and Kitt Peak National Observatory near Tucson, Arizona. She and Carnegie scientist W. Kent Ford used radio-telescopes to observe quasars, the faintest and most distant objects known. Photo Credit: Carnegie Science

Rubin and collaborator Kent Ford turned their observational attention to our closest neighboring galaxy where they discovered something quite unexpected. Given the way gravity works, stars far from a galaxy’s center should tend to circle the center more slowly than those closer in. But that’s not what the two astronomers observed. In the outer reaches of the galaxy, all of the stars were circling at the same speed.

But how? Was there some unknown force at work? Did the theory of gravity need an overhaul just as Einstein had overhauled Newton’s laws? Perhaps. But perhaps there was another answer.

It turns out that experimental observations can be explained without modifying the laws of gravity if it’s assumed there’s more matter than meets the eye. So-called dark matter, if dispersed properly, can account for everything we see — except for dark matter itself, which we can’t see. Nor can we hear, feel, smell, or taste it. We only know it through its gravitational effects.

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Artist rendition of the Milky Way Galaxy. Photo Credit: Wikimedia Commons/ESO/L.Calçada

Dark matter. Dark Energy. The Big Bang. Our universe can quickly get a little overwhelming. But Vera Rubin had an interesting way of putting things in perspective. “Galaxies may be pretty remarkable,” she said, “but to watch a child from zero to two is just incredible.”

I’m Andy Boyd at the University of Houston, where we’re interested in the way inventive minds work.

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R. Panek. The 4% Universe. New York: Houghton Mifflin Harcourt, 2011. In particular, see chapters 2 and 3.

This episode was first aired on April 7, 2016