Assistant Professor of Physics Tristan Smith has received a NASA grant to support his work in developing new ways to identify and measure the physics of the dark universe.

“We’ll be using data from a variety of cosmological probes,” says Smith, “including measurements of the Big Bang’s afterglow — known as the cosmic microwave background — of how galaxies cluster on the largest cosmological scales, and measurements of how the brightness of supernovae change as a function of their distance from us.”

Smith will conduct his research with Haverford Assistant Professor of Physics Daniel Grin. The pair were graduate students together at the California Institute of Technology and are excited to work together as part of a Tri-Co collaboration that is a testament to their shared perspective on teaching and scholarship.The $436,808 NASA grant will be shared between the two institutions. 

“Our goal is to develop new techniques to map out the expansion of the universe further back in time than has been done before,” says Smith.

It’s complicated work, because not only is the universe growing — it’s accelerating.

Most physicists agree that the dark universe consists of some sort of dark energy, dark matter, and neutrinos, Smith says. Though common approaches to computing the effects of these materials are typically reasonable, they can often be unverified. He’s determined to carve new paths in exploration.

“Our work will do away with many of those assumptions in order to best position us to make new discoveries,” Smith says.

David Robinson ’19, an honors physics and mathematics major from Tucker, Ga., is working alongside Smith on the research. Robinson is modifying existing cosmology code to include a highly generalized “dark fluid,” as well as theoretically modeling how a combination of dark energy and dark matter behaves as a single, effective dark fluid. 

“This project has been a great chance for me to apply and extend what I’ve learned in physics and math classes to a fascinating and exciting problem,” says Robinson, “and there have been a few surprising parallels with areas of physics I had thought were completely unrelated to cosmology.”

What exactly is dark matter, though?

Think of it as gravitational glue holding galaxies together, says Grin. Within the universe’s energy budget, he says, just under 30 percent is this mysterious substance.

“And 68 percent of the energy budget is an even more mysterious substance called dark energy,” he adds, “which dominates the universe today.”

Smith and Grin will treat the entire dark sector of the universe as a single dark fluid, with relationships between physically intuitive quantities like pressure, shear, and density set by free mathematical functions, says Grin.

“When you were taught about the scientific method in school, it was probably presented as a clear procedure: make observations that inspire a hypothesis and then test that hypothesis with new observations,” Smith says. “What I think is missing from this description is that observation is never purely objective: Whenever we ‘observe,’ we are doing so through some sort of framework, which can be surprisingly rigid and can blind us to new things.”

With this project, the team hopes to “see through” our current cosmological framework, opening up new avenues for discovery, Smith says.

“I am very excited to see how far we, and our students, are able to peek through to the currently unknown and unimagined,” he says.

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