By Stuart Clark – newscientist.com
SPARE a thought for the dark-matter hunters. Every time they’re on the verge of trapping the elusive stuff thought to make up the bulk of the universe’s matter, it slips away. They don’t see the expected signals, or they spot something exciting only to watch it fade into background noise. Each time it’s the same: put on a brave face, go back to the drawing board and begin the hunt again.
Perhaps it’s time for a change of tack. Instead of going after a single species of dark matter particle, maybe we should be looking for a menagerie of dark particles and forces – a whole new “dark sector”. After all, there is no reason to think dark matter will be any less intricate than the visible stuff we consider ordinary, with its panoply of particles from electrons to quarks.
“If you look at normal matter, our universe is enormously complicated,” says Alex Drlica-Wagner, a dark matter hunter at Fermilab near Chicago, Illinois. “So it may be naive to think that the dark sector is exceptionally simple.”
The talk is of an entire shadow world in which invisible particles influence one another through forces unfelt by the familiar stuff of stars and planets and us. A quixotic idea? Perhaps not. If the faint hints of a dark force emerging from one lab stand up to scrutiny, this shadow realm may already have revealed itself.
From as early as the 1930s, astronomers could see that galaxies orbit each other much faster than expected given the gravitational tug produced by their visible stars. Forty years on, (….)
—Read more here: https://www.newscientist.com/article/mg23130880-100-shadow-worlds-have-we-seen-our-first-glimpse-of-dark-forces/?utm_campaign=Echobox&utm_medium=Social&utm_source=Facebook&cmpid=SOC|NSNS|2016-Echobox#link_time=1472225614