Theorist Evelyn Tang sometimes feels like a translator caught between “two very different worlds.” She’s drawn to both physics and biology by a sense of awe and wonder, and her research seeks to use the power of physics to reveal fundamental truths about the living world.
“I’ve always looked for a sense of beauty and wonder and discovery,” said Tang, an assistant professor of physics and astronomy and senior scientist at the Center for Theoretical Biological Physics. “It’s not an accident that I like physics. There’s a real elegance and sense of beauty that speaks deeply to me.”
Her attraction to biology stems from a deep fascination with emergence — a concept describing collective behaviors that cannot be deduced from individual components. As an example, she cites the thought you are formulating as you read this sentence.
“If you ask neuroscientists how thoughts arise out of the firing of many individual neurons in our brains, they have no idea,” she said. “The neurons are tiny and fire very fast, yet collectively they somehow produce thoughts that we hold in our heads for minutes, hours, even lifetimes.”
Emergence happens often in biology, and at many scales, from the molecular action of proteins to the flocking of birds or schooling of fish. But biology is so complex that few unifying physical theories have been applied to emergence across different living systems.
“As physicists, we want to know, ‘Can we use our physics insights to understand the biological world?’” Tang said. “The challenge is to develop the physics tools that can help us understand how complexity arises in self-propelling, energy-consuming beings.”
Her group has begun adapting mathematical tools from topology, a branch of mathematics that has been used for decades by quantum theorists.
“In quantum systems, topology has been used to describe or make predictions across many different platforms,” Tang said. “It just says that if you have these kinds of shapes or these kinds of symmetries, then you get these kinds of outputs, which is very powerful.”
In recent work, her team mathematically mapped tools from quantum systems to biological systems and showed that biological systems can exhibit some of the same properties that exist in quantum topological systems. These include “protected” topological states, physical states that are difficult to perturb due to immutable mathematical properties. One surprising result from the work relates to the energy efficiency of biological circadian clocks, the internal clocks cells use to schedule daily tasks.
“Normally, to get a better clock, adding energy is your only recourse,” Tang said. “But we found that when a system becomes topological, it enters a very efficient regime where it doesn’t need as much energy to become a better clock.”
For Tang, physics is about more than seeking eternal and unchanging truths; it is about understanding the fragile and fleeting nature of life itself through elegant, predictive theories. “It’s even more fascinating to figure out how physics — these eternal principles — relate to the things we see in the world that are so complex and messy and unique,” she said.
As a mentor, she said one of her goals is to ensure students hold on to the sense of wonder and beauty that makes research both rewarding and enticing. “I hope they can keep strong their ideals and the love for the truth that started them in the first place.”
To remind herself and her students of that, she keeps a framed quote by 20th-century mathematician and philosopher Simone Weil on her office wall: “Stars and blossoming fruit trees: Utter permanence and extreme fragility give an equal sense of eternity.”