The Mystery of Matter: A Cosmological Explanation of the Origin of Mass

man in yellow shirts poses for picture

Stephon Alexander

"The universe is a big place and a mysterious one," Stephon Alexander told an attentive audience last Wednesday in the Penn State Downtown Theatre.

Alexander, assistant professor of physics, astronomy, and astrophysics, captivated Research Unplugged attendees with a discussion on the cosmological mystery of matter at the final event of the fall season.

Citing Einstein as his personal hero, Alexander opened the conversation with a reminder of the legendary physicist's contributions to the field. "Einstein questioned everything," he said, "including things that everyone else took for granted."

Alexander then led the crowd of colleagues and community members on a foray through such complex concepts as Einstein's theory of relativity, the expanding universe, and dark matter.

"Einstein's theory of relativity brought space and time together as a single four-dimensional continuum that contracts and expands to create a curving of space-time," he explained. "The curving allows matter to move, and that's what we call gravitational force."

"In outer space, you're weightless," Alexander continued. "But because of acceleration, you will actually experience the sensation of weight. If you are at rest on Earth, you will also experience w eight." Said Alexander, this phenomenon, called the equivalence principle, reinforces Einstein's theory that there is no way to make an absolute statement your state of motion. "He believed there must be a more universal explanation to simultaneously explain both situations, and that's the curvature of space and time."

"Einstein's theory predicts that the universe is an expanding collection of galaxies which emerge from a primordial quantum soup," Alexander said. "Our observations now show that the universe is mostly empty and void of matter, except for the five percent that consists of galaxies and stars."

"The flaw of Einstein's theory," he commented, "is that it predicts a smooth universe. The problem is that matter, including us, is part of our universe. And we're not that smooth—except for any smooth talkers out there," he joked.

Alexander explained that as the early universe expanded, "wrinkles and valleys" developed in the gravitational field that is the very fabric of spacetime. Those dimples in the otherwise smooth field created "holes that provided space for matter to fall into, similar to an object tumbling down a hill. "The hill represents gravitational force," he said. Eventually, the matter in these spacetime "valleys" accumulates more densely and becomes the stuff of galaxies.

An accomplished jazz saxophonist, Alexander went on to describe what he called "the universe on a riff," breaking down the complicated physics of the universe in terms of sound.

"When you listen to an orchestra on the radio, the sound is amplified by a microphone and transmitted via radio waves," he explained, noting that a radio wave is nothing more than high frequency light. "It takes a few microseconds—not even an eye wink—to travel 100 miles."

Alexander compared gravity to the bows and strings of that orchestra's instruments, noting that both create vibrations. "The first structure formed in the universe was a sound phenomenon," he added. The oscillations of radiation from the Big Bang are still reaching Earth. Because these primeval waves unfold in roughly 50,000 one-year cycles, they are "equivalent to the notes 50 octaves below the key of middle A," Alexander explained.

Astronomers have transposed the "score" up all those octaves so it is audible to human ears, revealing an "aural picture" with a range of low moans, loud roars and hisses.

Describing the collaborative work of Penn State's Institute for Gravitation and the Cosmos with centers such as CERN—the world's largest particle physics laboratory—in Geneva, Switzerland, Alexander referred to the strength of Penn State's physics department. "Our Center for Gravitational Wave Physics facilitates exciting interdisciplinary research among colleagues in astrophysics, gravitational wave physics and experimental gravitational wave detection," he said.

"We at Penn State are looking at the mystery of matter from different perspectives," Alexander concluded. "We're trailblazing the topic. So stay tuned."

Stephon Alexander, Ph.D., is assistant professor of physics, astronomy, and astrophysics in Eberly College of Science; sha3@psu.edu.

Last Updated November 12, 2007