Very early dark energy (vEDE) may have accelerated the universe’s expansion just 380,000 years after the Big Bang, according to newly published research.
This proposed form of dark energy would have shared characteristics with the mysterious force driving cosmic acceleration today, but would have behaved differently in the early universe. Instead of altering the cosmic microwave background radiation we still detect, researchers at the University of North Carolina at Chapel Hill say vEDE would have subtly changed how matter clumped together, influencing the formation of galaxies and cosmic structures billions of years later.
The recent findings were published in a paper that appeared in Physical Review D.
Very Early Dark Energy
“Think of our universe as a sheet that’s being stretched out,” lead author Alex Sobotka said. “Dark energy is causing space-time to evolve and warp, creating that stretching.”
Current estimates suggest the universe contains roughly 2 trillion galaxies, each with billions of stars and planets. Under Einstein’s theory of general relativity, these objects drift apart as the universe expands, with space and time forming a single fabric shaped by matter and energy.
“When we say the universe is expanding, that’s based on Einstein’s theory of general relativity,” he said. That theory treats the dimensions of space — up-down, left-right, back-forth — and time as part of the same fabric. Matter, like planets and stars, warps that fabric, determining how it stretches and evolves.
In the new study, Sobotka and colleagues propose a brief epoch in which the early universe was dominated by “very early dark energy.” During this period, changing energy density altered the balance between matter, radiation, and the aftermath of Big Bang nucleosynthesis. As a result, certain scales of the matter power spectrum — a key measure of how matter was distributed — were enhanced, while others were suppressed. These subtle shifts shaped the building blocks of today’s galaxies.
Modeling the Early Universe
Sobotka and UNC physicist Adrienne Erickcek collaborated with Tristan Smith of Swarthmore College to model how vEDE would influence the evolution of galaxies from the universe’s earliest structures.
The team used measurements of the cosmic microwave background — the faint afterglow of the Big Bang first detected in the 1960s — to inform their simulations. Though invisible to the naked eye, this ancient radiation serves as a cosmic fossil, preserving the initial conditions of galaxy formation.
“We predicted that if very early dark energy existed then, we should observe certain things today,” Sobotka said.
Impact of vEDE
One key prediction is that vEDE would increase the number of dwarf galaxies across the cosmos — including those orbiting the Milky Way. Soon, astronomers will be able to test that idea using Chile’s Vera C. Rubin Observatory, which begins full-sky survey operations this fall using the world’s largest astronomical camera. If vEDE shaped the universe, Rubin may reveal its fingerprints.
“We are on the cusp of potentially being able to see the signatures that our model predicted,” Sobotka said. “We stuck something interesting into the early universe to see the implications for the present-day universe. And we can use current observations to learn about what happened when the universe was a fraction of its age.”
The paper, “Signatures of Very Early Dark Energy in the Matter Power Spectrum,” appeared in Physical Review D on June 13, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.