Only four percent of the universe is made of materials we sort of understand. So what about that remaining 96%? For the most part we’ve labeled it under two names, dark matter and dark energy. We have no clear idea what these materials are. But now astronomers at the University of St Andrews are attempting to “simplify the dark side of the universe”. They say the two most mysterious constituents in the universe are actually the same thing.
(Image is the future Supernova Acceleration Probe which may help solve of the dark matter/dark energy mystery).
Dr HongSheng Zhao, of the University’s School of Physics and Astronomy, found that the puzzling dark matter and its counterpart dark energy are so closely intertwined that it’s not clear that they’re even two different materials.
A British astrophysicist and Advanced Fellow of the UK's Science and Technology Facilities Council, Dr Zhao points out, “Both dark matter and dark energy could be two faces of the same coin.
“As astronomers gain understanding of the subtle effects of dark energy in galaxies in the future, we will solve the mystery of astronomical dark matter at the same time. “
Many astronomers believe that both the universe and galaxies are held together by the gravitational attraction of a huge amount of unseen material. This idea was first noted by the Swiss astronomer Fritz Zwicky in 1933, and now commonly referred to as dark matter.
Dr Zhao reports, "Dark energy has already revealed its presence by masking as dark matter 60 years ago if we accept that dark matter and dark energy are linked phenomena that share a common origin.”
In Dr Zhao’s model, dark energy and dark matter are simply different manifestations of the same thing, which he has considered as a ‘dark fluid’. On the scale of galaxies, this dark fluid behaves like matter and on the scale of the Universe overall as dark energy, driving the expansion of the Universe. Notably, his model, unlike many other works, is detailed enough to produce the same 3:1 ratio of dark energy to dark matter as predicted by cosmologists.
Efforts are currently underway to hunt for very massive dark-matter particles with a variety of experiments. According to Dr Zhao, these efforts could turn out to be fruitless. The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva is a particle accelerator that amongst other objectives, an many hope it could potentially detect dark matter particles.
"In this simpler picture of universe, the dark matter would be at a surprisingly low energy scale, too low to be probed by upcoming Large Hadron Collider,” said Zhao.
“The search for dark-matter particles so far has concentrated on highly-energetic particles. If dark matter however is a twin phenomenon of dark energy, it will not show up at instruments like the LHC, but has been seen over and over again in galaxies by astronomers."
However, the Universe might be absent of dark-matter particles altogether. The findings of Dr Zhao are also compatible with an interpretation of the dark component as a modification of the law of gravity rather than particles or energy.
Dr Zhao concluded. “No matter what dark matter and dark energy are, these two phenomena are likely not independent of each other.”
Cosmologists agree that understanding the nature of dark matter and dark energy is key in understanding the expansion of our universe.
“Explaining why the expansion of the Universe is currently accelerating is certainly the most fascinating question in modern cosmology,” says Luigi Guzzo, lead author of a recent paper on the subject in the journal Nature. “We have been able to show that large surveys that measure the positions and velocities of distant galaxies provide us with a new powerful way to solve this mystery.”
Ten years ago, astronomers made the startling discovery that the Universe is now expanding at a faster pace today than it used to.
“This implies that one of two very different possibilities must hold true,” explains Enzo Branchini, who is working with Guzzo to unveil the mystery. “Either the Universe is filled with a mysterious dark energy which produces a repulsive force that fights the gravitational brake from all the matter present in the Universe, or, our current theory of gravitation is not correct and needs to be modified, for example by adding extra dimensions to space.”
Recently professor Jose Senovilla, and his colleagues at the University of the Basque Country in Bilbao, Spain, has recently proposed a mind-bending alternative to dark matter and energy. Their model shows that if time itself is slowing down, as in accordance with their new theory, our solitary time dimension is slowly turning into a new space dimension. Therefore the far-distant, ancient stars seen by cosmologists would from our perspective, look as though they were accelerating.
"Our calculations show that we would think that the expansion of the universe is accelerating," says Prof Senovilla. The theory bases it’s idea on one particular variant of superstring theory, in which our universe is confined to the surface of a membrane, or brane, floating in a higher-dimensional space, known as the "bulk". In billions of years, time would cease to be time altogether.
"Then everything will be frozen, like a snapshot of one instant, forever," Senovilla told New Scientist magazine. "Our planet will be long gone by then."
Though radical and in many way unprecedented, these ideas are not without support. Gary Gibbons, a cosmologist at Cambridge University, say the concept has merit. "We believe that time emerged during the Big Bang, and if time can emerge, it can also disappear - that's just the reverse effect."
In other words, these are all very interesting theories. Only time will tell—assuming it doesn’t run out before then.
Posted by Rebecca Sato
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