A new discovery from the Dark Energy Spectroscopy Instrument (DESI) may challenge one of the most important ideas in modern cosmology: that dark energy is constant.
If this turns out to be true, it could mean that much of what we think we know about the universe’s history—and future—needs to be rethought.
DESI is a powerful tool that maps the three-dimensional positions of galaxies.
It’s located on the Mayall Telescope in Arizona and has already mapped the positions of 15 million galaxies.
The most distant light captured by DESI is from galaxies whose light began traveling to us 11 billion years ago—when the universe was just a fifth of its current age.
Using this data, scientists studied the way galaxies are spread out across space, focusing on a pattern called baryon acoustic oscillations.
When compared to other data—like the cosmic microwave background and light from exploding stars—they found clues suggesting that dark energy might not be constant after all.
Dark energy is the mysterious force that makes up about 70% of the universe and causes it to expand at an accelerating rate.
Scientists once believed it could be explained by something called the cosmological constant, first introduced by Albert Einstein.
The idea is that this energy has stayed the same throughout the history of the universe. But the DESI findings suggest it may actually change over time.
If dark energy is not constant, the effects would be huge. Our current model of the universe, called the Lambda Cold Dark Matter (ΛCDM) model, is built around the idea that dark energy is a constant force. A changing dark energy would force scientists to come up with a completely new model of the universe.
One idea, introduced decades ago, is that dark energy may only dominate for a limited time. This would mean the universe’s current rapid expansion could eventually slow down and even reverse—possibly leading to a “Big Crunch,” where everything collapses back into a dense state.
While this theory is exciting, scientists remain cautious. Extraordinary claims, as Carl Sagan once said, need extraordinary evidence. More research is needed to confirm this idea. Other projects like the Euclid mission and the J-PAS survey are now gathering more data to study dark energy and how the universe is expanding.
Whether or not dark energy changes over time, this moment marks an exciting time for cosmology. We are closer than ever to uncovering the secrets of the universe—and maybe even rewriting its history.
Source: KSR.
