Dark Energy may be changing and with it the fate of the Universe

There is growing debate over recent evidence suggesting that a mysterious force known as dark energy may be changing in ways that challenge our current understanding of time and space.

Analysis by a South Korean team hinted that instead of the Universe continuing to expand, galaxies could be pulled together by gravity, leading to what astronomers call the “Big Crunch.”

The scientists involved believe they may be on the verge of one of the biggest discoveries in astronomy for a generation.

Other astronomers questioned these findings, but these critics could not completely discount the South Korean team’s claims.

Astronomers previously thought that the expansion of the Universe, which began with the Big Bang about 13.8 billion years ago, should gradually slow down due to gravity.

Later, in 1998, evidence for dark energy as a force accelerating the expansion of the universe was discovered. Studies of very bright exploding stars, called supernovae, have shown that distant galaxies are actually accelerating away from each other, rather than slowing down.

Some theories have suggested that this ever-accelerating Universe may first scatter stars so far that almost nothing can be seen in the night sky, and, even more surprising, eventually tear even atoms apart in a “Big Rip.”

Eventually, some astronomers thought that the expansion would slow down under the force of gravity and then gradually collapse in on itself; They called it the Great Crash.

This year’s provisional results now support that theory.

The controversy began in March with the unexpected results of an instrument called the Dark Energy Spectroscopic Instrument (Desi) located on a telescope in the Arizona desert.

Desi was built to discover more about dark energy. It tracked the acceleration of millions of galaxies in minute detail, but astronomers were not expecting the results it revealed.

According to Prof Ofer Lehav from University College London, who was involved in the Desi project, the data implied that the acceleration of galaxies was changing over time, contradicting the standard picture.

“Now that the changing dark energy is moving up and down again, we need a new mechanism. And that could be a shake-up for all of physics,” he says.

Later in November The Royal Astronomical Society (RAS) published the research From a South Korean team that supports the view that the weirdness of dark energy is even stranger.

Professor Young Wook Lee of Yonsei University in Seoul and his team went back to the supernova data that first revealed dark energy 27 years ago. Instead of treating these stellar explosions as having a single standard brightness, they adjusted for the ages of the galaxies they came from and calculated how bright the supernovae actually were.

This adjustment showed that not only was dark energy changing over time, but surprisingly, its acceleration was also slowing down.

“The fate of the universe will change,” Prof Lee told BBC News harshly.

“If dark energy is not stable and is weakening, this will change the entire paradigm of modern cosmology.”

If the force pulling galaxies apart (dark energy) is weakening, as Prof Lee’s results show, then one possibility is that gravity could weaken enough to bring the galaxies back together.

“Instead of ending in a Great Crunch, the Great Crunch is now a possibility.

“Which outcome wins out depends on the true nature of dark energy, which we don’t yet know the answer to,” says Prof Lee.

Prof Lee’s work was checked by fellow experts and published in a reputable journal of the RAS. However, his claims did not go down well with many senior astronomers working in the field, such as Prof George Efstathiou of the Institute of Astronomy at the University of Cambridge.

“I think it just reflects the intricate details of supernovae,” he says. “The correlation with age is not very tight, so I think it’s dangerous to ‘correct’. It looks weak to me.”

The mainstream view is that the Universe is still accelerating with almost unchanged dark energy.

But Prof Lee strongly disputes such criticism.

“Our data is based on 300 galaxies. The odds of statistical significance occurring by chance are roughly one in a trillion. So I feel strongly that our research is already very, very important.”

Since the South Korean results, the two teams have reassessed the brightness of some supernovae. They looked at an earlier study that fed into the Desi results from March, which started all this turmoil. They did this to double-check the March results because the claim that dark energy was changing was so controversial.

Both teams retreated slightly from the original clues, but even after extensive review the clues did not disappear.

As a result, there will continue to be passionate, sometimes contentious debates about whether the cosmos is gently whispering to us about its true nature, or whether astronomers are chasing ghosts in the sky.

Hundreds of scientific papers have been published on the subject, and astronomers are divided on what the best explanation is. According to RAS Deputy Director Prof Robert Massey, this is not a bad thing.

“Who doesn’t want to understand how the universe ends and how it began?” he says. “Whether you look at it from a religious perspective or a scientific perspective, human beings have always been interested in this.

“To be able to think, okay, billions of years from now, this is how things will end, wouldn’t that be extraordinary?”