The expansion rate of the universe is slowing down compared to a few billion years ago

Signals of the rate of change in the universe were detected by the Dark Energy Spectroscopy Instrument (DESI ), located atop the telescope at Kitt Peak National Observatory in the US state of Arizona.

 The DESI instrument at the Kitt Peak National Observatory in the US state of Arizona has detected signals of the expansion of the universe. (Photo: AFP).

The universe is still expanding at an increasingly rapid rate, but it may have slowed more recently than it did a few billion years ago. This is a preliminary result from the most accurate measurement of the universe's evolution announced by scientists on April 4.

Although these initial findings have yet to be confirmed, if proven correct, they would add to the mystery of dark energy and show that our understanding of the universe is still patchy. important deficiency.

Each of the device's 5,000 fiber-optic robots can observe a galaxy for 20 minutes, allowing astronomers to chart what they call the largest-ever 3D map of the universe .

 DESI is on a mission to unravel the nature of dark energy. (Photo: Reuters)

Arnaud de Mattia, one of the team's lead members, explains the DESI data: 'We measured the positions of galaxies in both space and time, because the farther away they are the more they rotate. back in time to a younger universe."

In just the first year of its five-year survey, DESI has created a map of 6 million galaxies and quasars using light reaching up to 11 billion years into the universe's past.

The results of this discovery were announced at conferences in the US and Switzerland on April 4, before a series of scientific articles were published in the Journal of Cosmology and Astroparticle Physics.

DESI is on a mission to unravel the nature of dark energy – a form of energy that is theoretically thought to make up about 70% of the universe. Another 25% of the universe is made up of dark matter, just as mysterious as dark energy, and only the remaining 5% is normal matter – all the stuff we can see.

For more than a century, scientists have determined that the universe began expanding after the Big Bang, 13.8 billion years ago. But in the late 1990s, astronomers were shocked to discover that the universe continued to expand at an ever-increasing rate.

This was a surprise because gravity from matter – both normal and dark – is thought to slow the expansion of the universe.

It's clear that something is causing the universe to expand at an ever-faster rate, and scientists have named this mysterious force "dark energy."

Recently, it was discovered that the acceleration of the universe increased significantly about 6 billion years after the Big Bang.

The cosmological model called Lambda CDM shows that in the 'tug of war' between dark matter and dark energy, dark energy seems to have the upper hand.

According to this model, the rapid expansion of the universe is called the 'cosmological constant', which is closely related to dark energy.

DESI director Michael Levi said that so far, the instrument's initial results show 'basic agreement with our best model of the universe. But we also see a Some interesting differences may indicate that dark energy is evolving over time."

In other words, the data 'seems to show that the Lambda cosmological constant is not really a constant,' because dark energy would display 'dynamic' and changing behavior, said Arnaud de Mattia.

DESI researcher Christophe Yeche said this could suggest that after 'accelerating' 6 billion years after the Big Bang, the expansion rate of the universe has "slowed down recently". '.

 According to the Lambda CDM cosmological model, the rapid expansion of the universe is called the 'cosmological constant,' which is closely related to dark energy. (Illustration photo: NICOLLE R. FULLER/SCIENCE PHOTO LIBRARY)

Whether dark energy in fact changes over time remains to be verified with more data from DESI and other instruments, such as the Euclid Space Telescope. But if confirmed, our understanding of the universe may have to change to accommodate this strange development.

For example, the cosmological constant could be replaced by some kind of field associated with some unknown particle. Arnaud de Mattia says we may even have to update the equations of Einstein's Theory of Relativity 'so that they behave a little differently on the scale of large structures.'

However, Mr. de Mattia also emphasized that that time is still very far away. And in the end, Einstein's Theory of Relativity over the past century, despite being subjected to many scientific analyzes and dissection, has always proven to be incredibly accurate and more convincing than ever.