The universe, a vast expanse born from the cataclysmic Big Bang approximately 14 billion years ago, continues to intrigue scientists with its mysterious components. While much of what we see and touch is composed of familiar matter, the elusive concepts of dark matter and dark energy play a more dominant role in shaping the cosmos, even as their true nature remains largely unknown.
Dragan Huterer, an associate chair and professor in the Department of Physics, delves into the complexities of the universe as a theoretical cosmologist. His work stands at the intersection of data theory and cosmology, a field distinct from astrophysics by its focus on universal phenomena like the Big Bang, dark matter, and dark energy.
Huterer highlights the paradox of our understanding: “We can’t answer why the Big Bang occurred or what existed before it…we arguably know more about the Big Bang aftermath than we do about the human brain, despite being able to physically study the brain.”
More than a century ago, scientists discovered that the universe was expanding. This expansion was initially attributed to dark matter, which binds galaxies together. However, the late 1990s brought about a revelation that challenged previous assumptions: the universe’s expansion was accelerating due to dark energy, a concept even more enigmatic than dark matter.
“It’s unclear exactly what dark energy is,” said Huterer. “It may be a new force, or possibly a particle with unusual properties causing the universe to expand faster and faster.” Initially, the universe was uniform, but over time, matter began forming galaxies. Dark energy opposes this aggregation by pushing matter apart, impacting the universe’s growth and structure.
Albert Einstein’s study of pollen particles in water mirrors cosmologists’ observations of galaxies, each acting as a particle in the cosmic dance. By examining these galaxies, the Dark Energy Spectroscopic Instrument (DESI) helps scientists understand the influence of dark energy on the universe.
The discovery of dark energy through distant supernovae observations, which earned the Nobel Prize in Physics in 2011, provided key evidence for the universe’s accelerated expansion. Huterer, who co-authored the first paper introducing the term “dark energy,” remains deeply involved in this research area, particularly with the DESI project.
Findings from DESI suggest that dark energy might be evolving over time rather than remaining constant. This challenges long-held beliefs and indicates a decrease in its effect on cosmic expansion over the past 4.5 billion years. DESI employs advanced mapping techniques, using 5,000 robotic arms to measure galaxy redshifts, creating a detailed 3D map of the universe’s expansion.
By analyzing baryon acoustic oscillations, scientists can track shifts in cosmic expansion rates. DESI’s sophisticated approach combines observational mapping and computational analysis, allowing researchers to explore potential changes in dark energy’s behavior and test cosmological models against theoretical predictions.
“Decades ago, cosmology was a purely theoretical field,” said Huterer. “But since the 1990s, it has become a highly quantitative science, producing vast amounts of data that have taught us so much about the universe.” Today, cosmology relies heavily on computation and simulation, rigorously accounting for potential errors in theory and observation.
The DESI project unites roughly 1,000 scientists to map the universe using the Kitt Peak telescope in Arizona, analyzing galaxy distributions to uncover large-scale cosmic patterns. “This work is heavily computational, but based on theory,” Huterer explains. The evolving understanding of dark energy continues to captivate scientists, offering exciting possibilities for future discoveries in our universe.
