Professor Justin Caram provides his insights into why molecules never stop moving, even at extremely low temperatures, in a recent Popular Science magazine article.
The article “Why Don’t Molecules Ever Stop Moving?” by Harriet Weber explores the concept of molecular motion and why it never ceases, even under extreme conditions. It delves into the relationship between temperature and molecular movement, explaining that temperature is proportional to the average kinetic energy of molecules. The higher the temperature, the more the molecules move. However, molecules never truly stop moving, even when scientists attempt to lower their temperature close to absolute zero. According to Caram, this is because molecules are always interacting with their environment—through collisions with other molecules or the absorption and emission of light.
Caram further explains in the article that quantum mechanics makes it impossible to fully stop molecular motion. The principles of quantum mechanics, including the uncertainty principle, prevent a molecule from having both zero momentum and a precisely measured position at the same time. The uncertainty principle states that you cannot simultaneously measure both the position and momentum of a molecule without introducing some level of motion. Caram describes this as one of the “strange aspects” of quantum mechanics, highlighting how quantum theory forces us to describe matter as having both particle and wave-like properties, which is counterintuitive to our everyday understanding.
The article shows that molecular motion is inherent, not just because of thermal energy, but due to the fundamental properties of quantum mechanics, making it impossible for molecules to stop moving entirely.
Caram earned his Ph.D. at the University of Chicago, studying quantum coherence and multidimensional spectroscopy under the guidance of Professor Greg Engel. He worked as a postdoctoral researcher at Massachusetts Institute of Technology (MIT) with Professor Moungi Bawendi, focusing on spectroscopy of fluorescent nanomaterials. In 2017, he joined the UCLA Department of Chemistry & Biochemistry faculty. His research group explores how molecules and materials interact with light, particularly through the study of exciton transport and system-bath interactions. Caram’s work blends chemistry, physics, and engineering, contributing to exciting developments in quantum science.
Caram is a founding member of the Center for Quantum Science and Engineering (CQSE), an interdepartmental program focused on advancing education for scientists and engineers in the field of quantum-enabled technology, including developing a terminal master’s degree program in quantum engineering.
His awards and honors include the Physical Division of the American Chemical Society 2024 Richard Van Duyne Early Career Award in Experimental Physical Chemistry, a 2023 Journal of Physical Chemistry and PHYS Division Lectureship Award, and a 2023 Sloan Research Fellowship.
Penny Jennings, UCLA Department of Chemistry & Biochemistry, penny@chem.ucla.edu.
