Hidden change in dark energy could rewrite the laws of physics

Dark energy may not be constant after all. DESI analysis of millions of galaxies shows signs that it may be evolving, suggesting a huge shift in cosmology

Dark energy: a changing constant?

A new analysis of three years of data from DESI (the Dark Energy Spectroscopic Instrument) strengthens evidence that dark energy, long assumed to be an unchanging "cosmological constant," is actually evolving over time in unexpected ways.

Dr. Mustafa Işık-Boşkaki is co-chair of the DESI working group responsible for interpreting the survey's cosmological data. The DESI collaboration includes more than 900 researchers from more than 70 institutes worldwide.

Although dark energy is still a mystery, many scientists agree that it plays a vital role in the accelerating expansion of the universe.

Is dark energy weakening?

The latest DESI findings, along with other measurements, add to the growing evidence that the effects of dark energy may be weakening over time, and that our model of the universe may need to be revised.

These supporting measurements include data from the cosmic microwave background radiation, the light left over from the early universe, along with observations of supernovae and weak gravitational lensing, which track how gravity distorts light from distant galaxies.

The researchers say that so far, the preference for evolving dark energy has not yet reached statistical significance at 5 sigma, the gold standard in physics that is the threshold value for a discovery. But various combinations of DESI data mixed with measurements of the cosmic microwave background, supernovae and weak gravitational lensing put the range at between 2.8 sigma and 4.2 sigma.

A point of no return for cosmology?

"With a significance of 4.2 sigma, I think we're reaching the point of no return," said Işık-Bushkaki. "In this new analysis, we not only confirmed our previous findings that dark energy is probably constantly evolving, we also increased their significance. What I think is most exciting is that the evidence comes from different data sets.

"I've been working on the question of the acceleration of the universe for 25 years, and my perspective is that if the evidence continues to strengthen, and it likely will, it will be a huge thing in cosmology and physics as a whole."

DESI has created the largest 3D map of our universe to date and is using it to study dark energy. Earth is at the center of this animation, and each dot is a galaxy. Credit: DESI collaboration and KPNO/NOIRLab/NSF/AURA/R. Proctor

DESI is one of the most comprehensive surveys of the universe ever conducted. The state-of-the-art instrument can capture light from 5,000 galaxies simultaneously. The experiment is now in its fourth year of surveying the sky and aims to measure about 50 million galaxies and quasars by the time the project is complete.

The new analysis uses data from the first three years of observations of nearly 15 million galaxies and quasars.

More of the topic in Hayadan:

• An invisible parallel "mirror universe" may be the reason for the disagreement about the Hubble constant
• Hubble reveals: dark energy has existed for at least 9 billion years
• "The discovery of the Nobel laureates is the most important discovery in cosmology in the last decades"
• The discoverers of the first planet outside the solar system and the key to the cosmological theory were jointly awarded the Nobel Prize in Physics
• A new model for dark matter and energy unifies the two