News24

Dark energy is real, researchers argue

2012-09-12 11:27

London - Dark energy, the mysterious cosmic force thought to be the fuel behind the accelerating expansion of the universe, is real, according to an Anglo-German team of astronomers.

After a two-year study, scientists at the University of Portsmouth in the United Kingdom and LMU University Munich in Germany have concluded that the likelihood of dark energy's existence stands at 99.996%.

That's the same level of certainty as this year's celebrated discovery of the Higgs boson, or a subatomic particle that looks very much like it, by scientists at the Cern research centre near Geneva.

Although accepted by many scientists as the best explanation for why the universe is expanding at an ever-faster rate, the theory of dark energy has its sceptics.

Astronomers studying the brightness of distant supernovae over a decade ago won the 2011 Nobel Prize for Physics for their conclusion that the expansion of the universe was accelerating.

Flotsam

But some scientists argue this is an illusion, caused by the relative movement of Earth in relation to the rest of the cosmos. Others suggest shortcomings in our understanding of gravity are more likely responsible than dark energy.

"Dark energy is one of the great scientific mysteries of our time, so it isn't surprising that so many researchers question its existence," said Bob Nichol, a member of the Portsmouth team involved in the research, which was published in the academic journal Monthly Notices of the Royal Astronomical Society.

"But with our new work, we're more confident than ever that this exotic component of the universe is real - even if we still have no idea what it consists of."

A basic premise of modern cosmology is that the visible universe of stars, planets and gases makes up about 4% of the cosmos and is sitting like flotsam in a massive sea of unknown material referred to as dark energy. Dark energy is thought to make up 73% of the cosmos, while the slightly less mysterious dark matter comprises the remaining 23%.

One of the strongest pieces of evidence for dark energy is in the so-called Integrated Sachs Wolfe effect.

In 1967, Rainer Sachs and Arthur Wolfe theorised that light from the radiation from the heat left over from the Big Bang, would become slightly more blue as it passed through the gravitational fields of lumps of matter in the universe, an effect known as gravitational redshift.

The existence of dark energy would cause light from this residual radiation to gain energy as it travels through large lumps of mass.

Square Kilometre Array

In 1996, astronomers Robert Crittenden and Neil Turok suggested overlaying a map of the local universe on the picture of the residual cosmic radiation could provide clues about where to look for the effect. In 2003, it was spotted, albeit weakly.

It was seen as supporting evidence for dark energy and hailed as the "Discovery of the Year" in Science magazine.

But some scientists argued it could have been caused by cosmic dust and questioned the discovery.

The Anglo-German team that carried out the latest study was led by Crittenden and Tommaso Giannantonio. They re-examined all the arguments against the detection and have improved the maps used in the original work.

They conclude that dark energy is almost certainly responsible for the hotter parts of the cosmic microwave background.

"We have methodically addressed all of these issues and concluded none of them can explain the observations we see," said Nichol. "In the end, the only remaining explanation is dark energy - if it walks like a duck and quacks like a duck, it's probably a duck."

Radio telescopes like the huge Square Kilometre Array, most of which will be sited in the Northern Cape province in South Africa, and a smaller part in Australia, should improve the tricky process of measuring distances in the universe and give more definitive data, he said.

"What dark energy could be, theoretically, is another question," Nichol said.

Comments
  • CaptainGaza - 2012-09-12 11:45

    And so the scientific method strides along, seeking the truth from what we can and cannot observe in this wonderful universe of ours.

      jody.beggs - 2012-09-12 12:05

      I would never be able to just believe something without seeing some evidence for it... Imagine where we would be without science and technology ? Damn the man.

      Jellyarse - 2012-09-12 13:26

      Damntheman - Like God?

      tommy.jones.754918 - 2012-09-12 13:45

      DTM, are you allowed to imagine? Anywoo, this is just amazing.

  • arthur.hugh - 2012-09-12 12:22

    Love it! Just had a weird thought. How does one measure if you're standing absolutely "still" in space - if ALL celestial bodies etc are moving at variable speeds etc.

      netizen.six - 2012-09-12 12:42

      You can't - its a General Relativity thing ;)

      CaptainGaza - 2012-09-12 12:45

      You can measure it's speed but not it's position or you can measure it's position but not its speed. The 2 cannot be done similtaneously.

      arthur.hugh - 2012-09-12 14:09

      Dang... That has messed up my day. Hope my kids never learn about it when I tell them to "sit still and behave" because they really CAN'T! lol.

      anakin.skyvader - 2012-09-12 15:59

      @CaptainGaza : That's the Heisenberg uncertainty principle you are referring to.

      TSR01 - 2012-09-12 16:47

      By measuring your relative speed through monitoring a stationery object, such as the sun. (Earth revolves around the sun at a rate of 365 days per cycle / orbit, or more specifically, at a rate of 29.9177km/second - call it 30km/second if you want). Also taking into account Earth's axis rotation speed of 27.83km/second (at the Equator), measurements based on observations of deep space can easily be calculated by distance from the amount of time light takes to travel from the observed point to Earth using highly sensitive and accurate radioscopy equipment. Mathematics has as important a role in astronomy as telescopes and electronic measuring equipment. (which calculate detected observations based on mathematically sound algorithms) So, actually, yes, you can measure the velocity / speed, size, distance and age since light takes time to travel from point A to point B, if we observe an explosion in deep space 100,000 light years away, we are presently observing a phenomenon which occurred at that location in that location's past (9460706.36km x 100,000) away. As a general point of interest, sunlight traveling across the Milky Way galaxy takes approximately 100,000 years to reach the edge of the expanse. A little knowledge goes a long way. :)

      neill.powell - 2012-09-12 22:05

      CaptainGaza has almost got it. the Uncertainty Principle is very valid at sub-atomic scales, where more precisely you attempt to determine a particle's location, the less accurately you can determine its momentum. A simple, but wildly incomplete basic interpretation is: Figuring out where a billiard ball is located while moving on a table, and the only way you know where it is, is by hitting it with another ball, shooting repeatedly from the same spot in different directions, as a result, you can then work out where you hit it, but not how fast it was going, or where it was going to, since you change its speed and direction as a result, funky stuff for sure. Relativity works on a macroscopic scale (salt grains and bigger), and yes, its pretty weird, but logical.

  • anakin.skyvader - 2012-09-12 12:45

    http://www.cheniere.org ....

  • chilli.stephenson1 - 2012-09-12 14:18

    God is so awesome.

      jody.beggs - 2012-09-12 14:42

      Fail ... God has nothing to do with man made in devours... Remember anything man made is evil , according to the buy bull and you only need to trust in the lord for everything you need. So give up technology and medicine and have faith in the lord to get you around and cure you. By using medicine and technology you're admitting god does not exist in your life because you lack faith. Damn the man.

      jody.beggs - 2012-09-12 15:20

      For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh, for these are opposed to each other, to keep you from doing the things you want to do. Still like information and fleshly things ... Not very godly is it.

      jody.beggs - 2012-09-12 15:47

      Of course no rebuttals from skittish xians who don't know their buy bull. What does the buy bull say about material possessions ? Good or Bad ? Idjits...

  • K9Lakhan - 2012-09-12 14:41

    "What dark energy could be..." JUJU cometh.

      CaptainGaza - 2012-09-12 15:45

      I wouldn't call Juju dark energy as that is not an accurate description, I'd say empty space is a more appropriate description.

  • JATRIZ1 - 2012-09-12 16:04

    @Neil and Rentie

  • walter.lebza - 2012-09-12 18:18

    This is not news. Looks like they don't know what they're talking about.

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