Almost 14 billion years ago, the universe gave birth to itself. In the manner of a glassblower shaping a molten orb, a tiny, exceptionally hot speck of dense material ballooned outward into vastness.
The event - known as the Big Bang - was an astounding burst of transformation. In less than a second, the universe likely doubled in size many times over. As it then began to cool, subatomic particles formed, followed minutes later by the lightest elements such as helium, hydrogen and lithium.
Remarkably, within just three minutes, the universe completed the first stage of its development. But it would take at least 100 million years - after the first stars ignited - for heavier elements to begin forming.
"It's hard to truly grasp how quickly the universe expanded and cooled during those first moments," says Kris Pardo, assistant professor of physics and astronomy. "Three minutes feels normal to us - but on that scale, it's almost impossible to comprehend."
Known Unknowns
Of course, the Big Bang remains a theory - "our current best guess" as to how the universe was formed, says Pardo. Key elements, such as "inflation" (a rapid expansion of the universe's size), still need confirmation.
"We think inflation likely occurred," he says, "mainly because it helps explain why our universe is geometrically flat, along with a few other cosmological puzzles. However, we haven't yet found direct evidence."
A key may lie in the cosmic microwave background, or CMB - a faint, lingering radiation that stretches to the edges of the universe. Dating back to just after the Big Bang, it serves as an invaluable cosmic clue.
Vera Gluscevic, associate professor of physics and astronomy, focuses much of her research on testing theories related to CMB. In April, she and Adam He, a doctoral student in physics, completed an analysis of data collected by the Atacama Cosmology Telescope, located in Chile's remote Atacama Desert. The images captured our clearest view yet of CMB - a snapshot of the universe when it was just 380,000 years old. Gluscevic and He were part of a team of 65 researchers from around the world who collaborated on this project.
It was a triumphant final round of images produced by the ACT, which was decommissioned in 2022. Gluscevic is now a research partner with the Simons Observatory Collaboration, also located in the Atacama Desert. It's home to the next generation of CMB telescopes, some of which are already in use at the observatory, with more on the way. These telescopes will enable scientists to study CMB with even more precision and will also produce the highest resolution images of the universe in its infancy ever captured.
"From this, we will learn not only about the origins of cosmic structures, conditions in the early universe, and dynamics of the whole universe across its history, but we will also answer some of the biggest questions about the fundamental quantum constituents of our physical reality, including neutrinos, dark matter and more," says Gluscevic.
Pardo's research focuses on dark matter, a mysterious, invisible substance found throughout the universe. Though it doesn't interact with light, dark matter exerts a gravitational pull that has shaped the very structure of the cosmos.
For the first 400,000 years after the Big Bang, strong radiation and electromagnetic forces prevented normal matter from coming together to form structures. But dark matter's relative imperviousness to these conditions allowed it to collapse into deep gravitational wells. As the universe cooled, ordinary matter fell into these pockets, eventually forming galaxies. Glittering night-sky spectacles, such as the Andromeda Galaxy and the Milky Way, owe their existence to this hidden cosmic scaffolding.
Pardo and Gluscevic co-lead the USC CosmoLab, a research hub for cosmologists and astrophysicists, based at USC Dornsife. The lab collaborates with scientists at institutions including Carnegie Observatories, the California Institute of Technology and NASA's Jet Propulsion Laboratory. It's also training the next generation of scientists who will advance our understanding of the universe's origins.
"CosmoLab has been important for us to both collaborate with nearby institutions, as well as bring that research to the many undergraduate and graduate students who work within the lab," says Pardo.
