The enigmatic idea of dark energy has consistently been referenced to explain the universe’s expansion, but new research may upend years of cosmological beliefs with a shocking claim made by scientists: dark energy doesn’t actually exist.
This revelation backpedals on a theory that astrophysicists have commonly followed in the hunt for answers to one of the universe’s most mystifying questions: how its perpetual expansion is possible. The endeavor to understand this concept may need to change direction entirely, according to a study published in Monthly Notices of the Royal Astronomical Society.
In the study, a team of researchers from the University of Canterbury in New Zealand asserts that the standard cosmological model used to interpret the framework of the universe should be dropped to make way for a more viable model that discredits dark energy and describes the universe as having a “lumpy” structure.
The Origins of Dark Energy
The traditional explanation for the universe’s growth centers around dark energy, presumed to be an imperceptible force that pushes space outward and makes up nearly 70 percent of the universe. Scientists have theorized that it interacts with dark matter, a hypothetical form of matter that has the opposite effect of holding galaxies together through its gravitational pull.
In 1998, astronomers claimed that the expansion of the universe was accelerating based on measurements of the brightness of Type Ia supernovae in distant galaxies; they proposed dark energy as the reason behind this trend, saying it counteracts gravity and accelerates expansion.
Since then, scientists’ understanding of the universe mainly revolved around the lambda cold dark matter model (lambda-CDM) — “cold,” meaning the matter is slow-moving, building the structure of galaxies.
Read More: What’s the Difference Between Dark Matter and Dark Energy?
Rethinking Universe Expansion
The current model of universe expansion is complicated by “Hubble tension,” an anomaly in which evidence from the afterglow of the Big Bang (known as the Cosmic Microwave Background) shows that the expansion of the early universe is not congruent with current expansion.
Another obstacle is that analysis from the Dark Energy Spectroscopic Instrument (DESI) operated by the Lawrence Berkeley National Laboratory has revealed that the lambda-CDM model does not fit as well as models in which dark energy evolves over time rather than remaining constant.
According to the researchers of the new study, Hubble tension and the DESI findings are difficult to resolve in models using Friedmann’s equation, which assumes that the universe is expanding uniformly.
The new study, however, strays from the idea of entirely uniform expansion. It provides evidence for a replacement called the “timescape” model, which frames the universe’s structure and expansion in a more irregular way.
Read More: A New Robotic Instrument Will Map Millions of Galaxies and Reveal Dark Energy’s History
What Is the Timescape Model?
The timescape model rejects the idea that dark energy is the driving force of universe expansion. Improved analysis of type Ia supernovae has suggested that the “acceleration” based on light curves seen in 1998 was a case of misidentification; the timescape model amends this by considering differences of time in void and matter-dense areas.
The model suggests that time moves much slower in matter-dense areas (like the Milky Way galaxy) than in voids. With more time passing in voids, increased expansion takes place, making it seem like expansion is accelerating as the voids increasingly spread through the universe. Dark energy, therefore, is not needed to explain the expansion of the universe, according to the researchers.
The recent implementation of the timescape model shows that the universe is expanding in a varied, “lumpy” way instead of expanding uniformly. It ultimately challenges the standard view of the universe, indicating that it may not be as homogenous as once thought and that “acceleration” from dark energy may have been a mistaken perspective of the universe’s growth this whole time.
Evidence supporting the timescope model has become stronger in recent years, but more testing is still needed. Researchers say the European Space Agency’s Euclid satellite will be able to make observations that could reinforce the model’s validity in the future. For now, the ambiguous identity of dark energy remains in limbo, and scientists may need to start looking at the universe in a different light.
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Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
