Jamie Bock: Building Detectors to Look for Evidence of Cosmic Inflation

In his search for evidence of cosmic inflation, Duke Physics alum Jamie Bock (B.S. ’87) uses on-ground telescopes, high-altitude balloons, rockets, and satellites. Bock is a professor of physics at Caltech as well as a senior research scientist at the Jet Propulsion Laboratory (JPL). “Our groups build one-of-a-kind instruments to answer questions about the early universe,” he says.

Cosmic inflation is the rapid expansion theorized to have occurred just after the Big Bang. “Inflation does make observable effects in the universe,” Bock says, “and one way you can get at it is through measuring the polarization of cosmic background radiation.”

Bock was one of four principal investigators on the BICEP2 project, which aimed to do just that. BICEP2 made headlines twice in the last couple of years. First, in March 2014, BICEP2 scientists announced they had measured a polarization pattern in cosmic background radiation that was consistent with the presence of gravitational waves—ripples in Einstein’s space-time continuum that are predicted in certain models of inflation.

The second set of headlines came in February of this year when Bock and colleagues collaborated with scientists on the Planck project (a satellite mission of the European Space Agency) to present evidence that the polarization pattern was at least partially due to galactic dust. “The Planck data, which weren’t available until this year, showed that galactic dust emission was more polarized and more variable over the sky than previously modeled,” Bock says. However, he’s not convinced that dust is the only contributor to the polarization: “All we can say right now is at least 40% of the signal is associated with dust. Unfortunately, the remainder is instrument noise, mostly from Planck. It’s frustrating, but that’s simply the limit of what we can do today with the world’s best data.”

To better understand the polarization pattern and what it represents, follow-up work is underway on BICEP3, which like its predecessor, is a ground-based telescope located at the South Pole. “The error bars will go down as our experimental observations at higher and lower frequencies surpass the [earlier] data,” Bock says. “We’re now at the sweet spot for seeing an inflationary polarization signal. Cosmologists have been talking about testing this regime for the last two decades. In the next few years—or maybe less—we will find out the answer. That’s pretty exciting.”

Bock is also working on a project called SPIDER, which uses a high-altitude balloon to make measurements of polarization. The balloon was launched on January 1 into the vortex of winds 120,000 feet above Antarctica. After a 10-day trip, it came down on the Chilean side of the continent which is “not a great place for access,” according to Bock. The data drives were recovered from the balloon in March, but excavating the rest of the equipment from a winter’s worth of snow, disassembling it, and flying it out will have to wait until the Antarctic winter subsides. Bock says the data look good at first glance, but full analysis will take a couple of years.

Another way to look for evidence of cosmic inflation is to study the large-scale structure and distribution of galaxies in the universe. Galaxies form in areas of high density, so understanding their structure could shed light on large-scale density fluctuations, which could contain clues to conditions immediately after the Big Bang.

Bock recently received a $1 million grant from NASA for an 11-month study to design a small satellite named SPHEREx. “With the satellite,” Bock says, “we will look at the distribution of galaxies in three dimensions over the whole sky and measure as many of them as we can. Together with the polarization measurements we can learn about exotic physics that powered inflation.” SPHEREx is competing with two other proposals for selection in 2017 to go forward with construction and launch in 2020.

As an undergraduate at Duke, Bock considered being pre-med but quickly discovered he loved science for its own sake. He sought out the astronomy classes, taught by Eric Herbst and John Kolena, and did some research with Hugh Robinson. Of his time at Duke, he says, “The one thing I definitely remember is the level of instruction in the physics classes was really excellent. Now that I’m teaching, I appreciate how hard that is.”

He also enjoyed playing the trombone and was in the marching band, wind symphony, and jazz band. Working with music professor and jazz great Paul Jeffrey, he and other members of the jazz band got to play with the likes of Wynton Marsalis and Dizzy Gillespie.

After Duke, Bock went on to earn his PhD at UC-Berkeley, where he discovered his aptitude for experiments. “It takes patience, but I find it very satisfying to build something and see it work—especially if it does something that hasn’t been done before.”

He’s been at Caltech and JPL since 1994. When not at work, you might find him running or spending time with his three daughters--or doing both at the same time. The oldest two run cross country and will be attending a running camp in the Sierras in late August. “I’m going to go too,” he says, “and we’ll see if I can keep up.”

Mary-Russell Roberson is a freelance science writer who lives in Durham.