Einstein May Have Been Right, but Is Our Understanding of Dark Energy Wrong?
For more than a century, astronomers around the globe have been challenging renowned physicist Albert Einstein’s theory of general relativity. While the latest findings from the Dark Energy Spectroscopic Instrument (DESI) collaboration further confirms general relativity, the findings have also upended astronomy’s understanding of dark energy.
Our universe is expanding at an accelerating pace, but astronomers don’t yet understand exactly why or how. First theorized in 1998, astronomers have a name for the force responsible for this acceleration: dark energy. Dark energy makes up nearly 70 percent of the universe—compared to just 5 percent for visible matter such as stars, planets, moons, asteroids, and everything else that we can see—and astronomers thought it was a constant force.
DESI’s findings show that the force is weakening, however, and that revelation has sent shockwaves across the astronomy world. If dark energy is getting weaker, it topples astronomy’s standard model for the energy content within the universe and how it has evolved over time.
It also means that the universe’s future may unfold differently than the field of astronomy has thought.
“Our standard cosmological model is that dark energy is a constant of empty space,” says Illinois Institute of Technology Assistant Teaching Professor of Physics Goni Halevi. “If it is actually becoming weaker as the universe expands, this has major implications for the future of our universe. In particular, our standard model suggests that the universe will keep expanding faster and faster, getting darker and colder as dark energy tears everything apart. But if dark energy is losing its power, a different end is possible.”
Interestingly, the results from DESI are completely consistent with general relativity’s predictions, upholding astronomy’s best theory of gravity yet again. But Halevi cautions against jumping to conclusions too quickly. While DESI’s data is significant, more evidence is needed.
“While there is compelling evidence based on the DESI analysis, we need more confirmation to call it a discovery,” says Halevi. “Huge state-of-the-art simulations of the universe that require a massive amount of computational resources typically assume our standard cosmological model, which we are now learning may not be accurate at all. It is already disturbing to think that we only truly understand 5 percent of our universe—the part that is made up of normal matter— but we are now learning that our already foggy picture of dark energy is even more incomplete than we had thought.”
