Shedding light on ‘dark’ energy‘Dark’ energy is one of cosmology’s greatest problems, but thanks to ground-breaking work carried out by the Durham University’s Institute for Computational Cosmology (ICC), published on 11 January, scientists have a clearer idea of how to go about measuring it. Dark energy is important because it is a repulsive force counteracting gravity that is estimated to make up 70% of the Universe. As a result, it is currently believed that it is responsible for the Universe’s observed accelerating expansion. If this expansion continues to accelerate, the Universe’s fate is not pleasant: a ‘big freeze’ where it is pulled apart and becomes a vast cold expanse of dying stars and black holes. A better understanding of dark energy is therefore important, which is why the ICC undertook its research. This was a series of computer simulations of the Universe on Durham’s Cosmology Machine (COSMA) computer that took 11 days to run. It 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. Interestingly, it was found that some of these delicate ripples survived the subsequent 13 billion years in certain conditions. Also, by changing the nature of dark energy in the simulations, they appeared to change in length and could act as a ‘standard ruler’ for the measurement of dark energy. ICC Director Professor Carlos Frenk explains this significance of this: ‘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.’ These findings will provide a vital input into the design of the SPACE (SPectroscopic All-sky Cosmic Explorer) satellite project led by Bologna University, Italy, which is intended to explore dark energy. The co-principal investigator, Professor Andrea Cimatti, of Bologna University, explains further: ‘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.’ If it gets the go ahead from the European Space Agency, it is planned to launch SPACE in 2017. Find out more about this and other world-beating research on the ICC’s website. |
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