Dark matter: Absence of evidence, or evidence of absence? Physicists are learning more about what dark matter isn’t. That will help them find out what it is – The Economist Nov 2nd 2013


COSMOLOGY and particle physics—or at least, the popular versions of them—tend to the grandiose. The Higgs boson, recently discovered at CERN, Europe’s particle-physics laboratory, is not just any old particle. To the despair of many physicists, it has been dubbed the “God particle”. Books on cosmology promise to reveal the “fabric of the cosmos”, while their academic authors discuss different flavours of a “theory of everything”.

The reality, though, is more disappointing—or perhaps more exciting, depending on your point of view. Physicists have excellent, accurate theories to describe the behaviour of the matter that makes up atoms. But they also know that this matter constitutes less than 5% of the substance of creation. The remainder is split between “dark energy”, a notional force assigned responsibility for the accelerating expansion of the universe, and “dark matter”, ghostly stuff whose existence seems necessary to make sense of the arrangement of the heavens. Both are the subject of intense study, and both remain deeply mysterious.

On October 30th the team running the Large Underground Xenon (LUX) experiment, in a mine 1,500 metres below South Dakota, announced the results of their first three months spent hunting for dark matter: nothing. That is big news. It contradicts evidence from several other experiments, which offered hints that dark matter had been spotted. And LUX is the most sensitive dark-matter detector yet built.

Article continues: http://www.economist.com/news/science-and-technology/21588829-physicists-are-learning-more-about-what-dark-matter-isnt-will-help-them-find

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