Recent results from the Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI) are giving us a radical new perspective on dark energy. Researchers recently proposed that dark energy is not constant at all, contradicting what most assumed was a settled mystery. For two decades now, astronomers had assumed that dark energy was a constant in our universe. New data from Dangerous by Design 2023 completely upends that rationale. It raises the possibility that dark energy is not only not constant, but perhaps it will factor significantly into cosmic expansion’s ultimate future.
The study used a unique and impressive combination of data sets. It included the Sloan Digital Sky Survey (SDSS), Time-Delay COSMOgraphy and the Planck+Atacama Cosmology Telescope. This cooperation resulted in the most accurate measure of dark energy to date. It forced specialists to reconsider age-old assumptions about the Corps’ nature and consequences.
As we’ve previously explored, dark energy, the mysterious force that makes up about 70 percent of the universe, is one of the biggest mysteries in cosmology. Though its presence is known for sure, scientists have tried and failed to understand its physical nature. For comparison, dark energy is estimated to be 38 orders of magnitude. This massive gap, no pun intended, makes our search for answers difficult.
Evolving Theories and New Models
These new findings show that dynamical models of evolving dark energy provide superior descriptions of observational data. This, too, is a huge advance over the naïve cosmological constant picture. Josh Frieman, a leading astrophysicist, inverts the telescope on the groundbreaking nature of this evolution as a measure of dark energy, said Frieman.
“This would be our first indication that dark energy is not the cosmological constant introduced by Einstein over 100 years ago but a new, dynamical phenomenon.”
In some of the evolutionary models, dark energy’s density is predicted to decline with time. In fact, recent deep-sky observations suggest that the density of dark energy has already decreased by 10% or more. This readjustment has occurred over the last few billion years. These results indicate that dark energy was probably pretty stable in the early universe. Eventually, it too is beginning to look a little different.
Theory suggesting that the acceleration of the universe’s expansion is lower than previously assumed. This discovery underscores the importance of directly measuring dark energy’s dynamics to change or refine predictions of what different future cosmic expansion scenarios might involve. Scientists suggest that the universe may face a cold, dark fate—a scenario often referred to as the Big Freeze—if the trends continue.
Implications for Cosmic Expansion
The implications of an evolving dark energy go much further than just the theoretical debate. Often, scientists put data from multiple surveys together to find a clearer picture of the history of cosmic expansion. They look at how quickly the universe was expanding at various epochs. Frieman noted,
“The data from these surveys allow us to infer the history of cosmic expansion—how fast the universe has been expanding at different epochs in the past. If dark energy evolves in time, that history will be different than if dark energy is constant.”
Astrophysicists have made a cause célèbre of the dark energy. For their part, they employ a potent combination of supernova observations, baryon acoustic oscillations, and cosmic microwave background data. The new combined constraints from the two largest datasets represent a powerful result in its own right. A theory-motivated, physics-inspired model of dynamical dark energy robustly rules out the standard model at 99.6% confidence.
In addition, physicists are investigating speculative particles such as axions to fill a similar role within dark energy. Physicists originally predicted axions in the 1970s. They invented these particles in order to account for certain observed characteristics of strong interactions found in particle physics. The combined efforts of particle physics and cosmology should continue to lead to new paradigm-shifting understandings of the dark energy’s strange essence.
Future Directions in Dark Energy Research
Scientists are understandably excited to buoys into the implications of these findings. We look forward to seeing how their continued research will continue to improve our understanding of the universe. The idea that dark energy could change over time allows for exciting new possibilities in both cosmology and particle physics to be explored.
Frieman expressed both concern and intrigue about the current state of knowledge regarding dark energy:
“It’s a bit embarrassing that we have little to no clue what 70% of the universe is. And whatever it is, it will determine the future evolution of the universe.”
The current experiments are trying to improve our measurements and come up with models that could explain this changing dark energy. Researchers hope to develop a more intuitive view of how the universe behaves on extremely long timescales. Now they’re interested in how it might live out its fate.