Super-computer could throw light on 'mysterious' dark energy
January 11, 2008Cosmologists have run a series of huge computer simulations of the Universe that could ultimately help solve the mystery of dark energy.
Results of the simulations, carried out by Durham University’s world-leading Institute for Computational Cosmology (ICC), tell researchers how to measure dark energy – a repulsive force that counteracts gravity.
The findings, published today in the Monthly Notices of the Royal Astronomical Society, will also provide vital input into the design of a proposed satellite mission called SPACE – the SPectroscopic All-sky Cosmic Explorer - that could unveil the nature of dark energy.
The discovery of dark energy in 1998 was completely unexpected and understanding its nature is one of the biggest problems in physics.
Scientists believe dark energy, which makes up 70 per cent of the Universe, is driving its accelerating expansion. If this expansion continues to accelerate experts say it could eventually lead to a Big Freeze as the Universe is pulled apart and becomes a vast cold expanse of dying stars and black holes.
The Durham research was funded by the Science and Technology Facilities Council and the European Commission
The simulations, which took 11 days to run on Durham’s unique Cosmology Machine (COSMA) computer, looked at tiny ripples in the distribution of matter in the Universe made by sound waves a few hundred thousand years after the Big Bang.
The ripples are delicate and some have been destroyed over the subsequent 13 billion years of the Universe, but the simulations showed they survived in certain conditions.
By changing the nature of dark energy in the simulations, the researchers discovered that the ripples appeared to change in length and could act as a “standard ruler” in the measurement of dark energy.
ICC Director Professor Carlos Frenk said: “The ripples are a ‘gold standard’. By comparing the size of the measured ripples to the gold standard we can work out how the Universe has expanded and from this figure out the properties of the dark energy.
“Astronomers are stuck with the one universe we live in. However, the simulations allow us to experiment with what might have happened if there had been more or less dark energy in the universe.”
In the next five to 10 years a number of experiments are planned to explore dark energy. The Durham simulation has demonstrated the feasibility of the SPACE satellite mission proposed to the European Space Agency’s (ESA) Cosmic Vision programme.
The project has been put forward by an international consortium of researchers including the Durham team.
SPACE, which is led by Bologna University, in Italy, is through to the next round of assessment by the ESA and if successful is planned to launch in 2017.
Co-principal investigator Professor Andrea Cimatti, of Bologna University, said: “Thanks to the ICC simulations it is possible to predict what SPACE would observe and to plan how to develop the mission parameters in order to obtain a three-dimensional map of the Universe and to compare it with the predictions of the simulations.
“Thanks to this comparison it will be possible to unveil the nature of dark energy and to understand how the structures in the Universe built up and evolved with cosmic time.”
Source: Durham University
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"Dark Matter" and "Dark Energy" are two completely different theoretical concepts.
Dark Matter is thought to consists of black holes and exotic particles which have gravity, but escape conventional forms of detection, thus theoretically explaining the so-called "missing mass" in galaxies and certain star clusters.
Dark Energy is the theoretical force which causes space-time expansion.
Until you put a hoverboard in my hands, PURE SPECULATION of anti-grav matter means jack.
IMO, the results can be explained with current information without the invention of new terms and phrases.
As far as the article goes, simulations of bad information don't shed light on anything.
Too true. A computer program can only do what it is programmed to do. In this case solve some differential equations (most likely approximately) and then blit them to the screen as an image. It doesn't "shed light on" anything. A person must solve a general algorithm, and consequently the general equations, before they can even begin to program a computer. Therefore the computer cannot tell you anything about a simulation that you could not have learned by solving the problem by hand.
Bad theory Bad evidence = bad model, regardless of how good the mathematics and computer simulations may be.
Right now, I consider "Dark Energy" to be about as scientific as the "Force" from Star Wars.
At best, one could view "Dark Energy" as a mere catch phrase for "All the stuff we don't know about physics."
In fact, most often you can substitute that phrase for "Dark Energy" and the sentence still holds true gramatically and contextually.
"The discovery of dark energy in 1998 was completely unexpected and understanding its nature is one of the biggest problems in physics."
This is a misleading statement which might lead an un-informed reader to think that scientists have ever actually "seen" dark energy in a lab or measured or tested it. They haven't.
The substance called "Dark Energy" could be almost anything, or it could be the product of several things which are otherwise unrelated, nobody knows. But that statment in quotes above makes it seem like someone already has a sample of it somewhere or something.
Dark Energy is undefined as of this time, though there are a number of differing models of what it might be or how it might interact with the rest of the universe. H owever, whatever Dark Energy is, as far as we know, it could be one or more forms of matter or energy, and not just one simple substance.
It could be.
DE = unknown energy/substance A
DE = B (an error in "law" of gravity!)
DE = A B
DE = A any number of other factors
DE = B any number of other factors
or
DE = A B any number of other factors
and so on.
One of the things that this kind of cavalier treatment of these stories leads to is for common joes on the street to see a story labelled "ZZZZ's idea about DE proven wrong" and then say "AHHA, See, Science was wrong again!". When if fact it is nothing more than someone's wild pet conjecture being disproven.
So Bohm found that in order to causally explain quantum wave diffraction in terms of hidden variables he needed to describe a distinct cause acting in addition to the forces, which he called the quantum potential. This cause needing to be described given that quantum objects are both particles or point objects with defined trjectories while in motion and also indefinitely extended waves which deflect the particle paths so as to cause diffraction pattern. While, unlike all the forces, the quantum potential would need to be nonlocal in that, unlike the four fundamental interactions, such a cause could not be described as acting as it surrounds objects in 3D space.
Then couple the Bohmian causal account with the evidence for the "proxy wave" - whereby the diametre of photon waves are measured to increase over astronomical distances, and it seems to me, you have the beginnings of a theory of 'dark energy' as a nonlocal "cosmic quantum effect".
And you can also think, well, what about the formation of cosmic voids as nonlocal quantum effects, and then... um... Galaxy and galaxy cluster formation?!!
What? Cosmic nonlocality?? Must be a cranky idea really, musn't it?
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