Baffling discovery about the universe expanding defies our understanding of physics

A new study has revealed the universe is expanding too quickly for our current understanding of physics to explain.

The expansion of the universe is described using a unit of measurement called the Hubble constant. Determining the universe’s expansion rate has been a major point of intrigue since 1929, when Edwin Hubble first discovered that our universe is expanding.

The universe began with the Big Bang, a rapid expansion from an initial state of high density and pressure.

Scientists now know that the universe is expanding in all directions, and the rate of expansion is accelerating. Experts can track how far away galaxies are from Earth, and how fast they’re moving away. The farther away a galaxy is, the faster it appears to be moving away.

Our current understanding of physics cannot explain why the universe is expanding faster than predicted by theoretical models. The disparity between model and data is known as the Hubble tension.

“The tension now turns into a crisis,” said physicist Dan Scolnic, from Duke University, per Phys.Org. He led a team in double-checking measurements of a galaxy cluster nearby.

Scolnic explains the research as attempting to build the universe’s growth chart. If we were to think about the universe compared to pictures, its baby picture represents the distant universe, or the initial small fluctuations that grew into the galaxies we see today. The current headshot represents the local universe, containing the Milky Way and its neighbours.

Unlike how you would likely be able to see how the baby snap grew into the contemporary adult, things don’t quite connect when it comes to the universe and how we understand its expansion and cosmology.

“This is saying, to some respect, that our model of cosmology might be broken,” Scolnic said.

A cosmic ladder is needed to measure the universe, which is a series of methods (or “rung”) used to measure the distances of celestial objects. Each method relies on the previous one for calibration.

Scolnic used a ladder created by a separate team using data from the Dark Energy Spectroscopic Instrument (DESI). It observes more than 100,000 galaxies each night from the Kitt Peak National Observatory. Scolnic realised this ladder could be anchored closer to Earth with a more precise distance to one of the galaxy clusters closest to us, called the Coma cluster, which is estimated to be roughly 320 million light-years away.

The universe is expanding rapidlyrawpixel.com

"The DESI collaboration did the really hard part, their ladder was missing the first rung," he said. "I knew how to get it, and I knew that that would give us one of the most precise measurements of the Hubble constant we could get, so when their paper came out, I dropped absolutely everything and worked on this non-stop."

Noting that the Coma cluster was 320 million light-years away, Scolnic said: "This measurement isn't biased by how we think the Hubble tension story will end. This cluster is in our backyard, it has been measured long before anyone knew how important it was going to be."

Scolnic and the team found that the local universe is expanding 76.5 kilometers per second faster every 3.26 million light-years. This value matches the universe's expansion rate as other teams have measured it in recent times, but it does not match our current understanding of physics predicts it to be.

"Over the last decade or so, there's been a lot of re-analysis from the community to see if my team's original results were correct," said Scolnic.

"Ultimately, even though we're swapping out so many of the pieces, we all still get a very similar number. So, for me, this is as good of a confirmation as it's ever gotten."

"We're at a point where we're pressing really hard against the models we've been using for two and a half decades, and we're seeing that things aren't matching up," said Scolnic.

"This may be reshaping how we think about the universe, and it's exciting! There are still surprises left in cosmology, and who knows what discoveries will come next?"

The research was published in The Astrophysical Journal Letters.

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