Dark Energy Might Not Be Constant, According To New Theory

Hubble image MACS J0717. NASA, ESA and the HST Frontier Fields team (STScI)

Dark energy is a mysterious force, a form of energy that is believed to accelerate the expansion of the universe. While it has been assumed to be a “cosmological constant”, researchers have now found evidence that suggests that dynamical dark energy might fit current observations better.

As reported in Nature Astronomy, the team used dynamical dark energy to try to solve a contentious point that has emerged in recent years: the value of the Hubble constant. The constant represents the rate of the expansion of the universe, and the two main methods we have to determine it get slightly different values. It’s not clear if this is due to an unknown systematic error or if there’s something wrong with our theory.

The latter idea is the starting point of the research. If dark energy changes over the ages of the universe, could this affect the rate of expansion? The two methods measure the rate of expansion at specific points in time, so they could both be correct, at least according to the dynamical dark energy model.

While this is definitely intriguing, the model with constant dark energy and dark matter (known as Lambda-CDM) continues to have the best agreement with the widest range of observations – although more refined models might challenge this.

“We are excited to see that current observations are able to probe the dynamics of dark energy at this level, and we hope that future observations will confirm what we see today,” lead author Professor Gong-Bo Zhao, from the University of Portsmouth and the National Astronomical Observatories of China, said in a statement.

There are many upcoming projects that could help us clarify the doubts and tell us if the dynamical dark energy model is a contender to our theory of the universe. Surveys like the Dark Energy Spectroscopic Instrument (DESI), which will begin next year, might already tell us something unexpected, and the Gaia Mission and the James Webb Space telescope will help as well in a similar time frame.

The accelerated expansion of the universe was only discovered at the end of the last century, and its mysterious cause was simply called dark energy. Almost 20 years later, we know a lot more about the universe and yet dark energy remains a big puzzle.

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