Professor McAllister

Courtesy Karen Zaklama

Professor McAllister

August 27, 2018

Cornell Professor Examines History of the Universe

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“Where did we all come from?” is the question Professor Liam McAllister, physics, tries to answer every day. McAllister’s research focuses on string theory, a cutting-edge scientific inquiry that remodels matter as a series of strings.

Part of string theory’s appeal to modern mathematicians and physicists is its ability to unite quantum mechanics and gravitational laws. Currently, physicists view the world as a composition of matter and energy and have been able to redefine the approach to understanding the molecular world. However, despite the important jumps quantum physics has allowed scientists to make, there are still questions about the magnitude or scale of quantum theory, especially in application to the early universe.

“For phenomena in nature, one can get away with not combining gravity and quantum mechanics,” McAllister said. “In the early universe, the density was high, which meant gravitational interactions were high. Quantum mechanics interacting with that kind of gravity is only present in the early universe.”

McAllister is particularly interested in the early state of the universe because it has never been fully characterized before.

“Understanding the early universe is an achievement that is not fully appreciated by the scientific community. Cosmology as a science is very young and until recently was perceived as speculative,” he said, referring to the discipline which studies the development of the universe and its origins. Cosmology is mainly studied by physicists and astronomers.

Despite its mathematical rigor, McAllister’s work on theoretical cosmology relies on little to no technology. With the exception of a few computing programs, McAllister works with pen and paper. “We use blackboards and chalk. Sometimes we use mathematical programs to do some algebra, but that is a very small percentage of the work we do,” he said.

Although a relatively young scientific field, McAllister discussed how the discipline has evolved.

“You know a subject has matured when basic principles are fully specified and the only problem that remains is solving the equations,” McAllister said.

“Cosmology is still very complex, but I can foresee that some parts of the theory are maturing. Today we have a vastly different picture of our origins from what has been discovered in just the past 25 years, and the math continues to validate theory.”

Perhaps McAllister’s rigorous scientific findings can offer some comfort to Cornell students. Cosmology has made strides as a science, evolving to unite gravity and quantum mechanics to reveal far more information about the beginning of the universe than ever before. Because of advances in math and physics, humanity can answer much bigger questions about its history.

“A development of a complete quantitative understanding of the universe, with well understood laws, is one of the really great historic triumphs in humanity’s endeavour to understand where we came from,” McAllister said. “There is a huge impact for people who look up at the sky and wonder.”

Working with something as expansive as the universe, McAllister has the perspective that students sometimes cannot see.

“There is a relationship between the large and the small,” he said. “If we dig a little deeper in cosmological history, we might be able see the interactions of quantum mechanics and gravity on a different level. We can have more insights into understanding why we are where we are.”

So next time you are wondering how we all got here, remember that there are people like Professor McAllister on this campus answering those questions with string theory.