An elegant assumption underpins our cosmic model: that everything looks the same everywhere. But does it make us see things that aren't there?
A DOOR flies open but no one's there. A vase levitates from the mantelpiece and hurls itself across the room. The furniture starts moving around of its own accord.
The universe today is a little like one of those ghost movies. Galaxies whirl around in unexplained ways. Groups of stars race across space, pulled by forces from beyond the visible universe. The fabric of space is inexplicably elastic, expanded ever faster by an inscrutable energy all of its own.
Not an overly superstitious bunch, cosmologists invent names for the poltergeists responsible – dark matter, dark flows, dark energy – and invest a lot of effort in proving they are real. But might they, too, be chasing ghosts? That's what some ...
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