Since both are affected by gravity they are attracted to each other, so the distribution of normal, visible matter acts as a proxy for the distribution of dark matter.

ECONOMIST: Astronomy

Two further refinements were necessary: to work out the third dimension distance from Earth and to subtract the effect of visible matter in order to be left with the distribution of dark matter pure and simple.

ECONOMIST: Cosmology: I spy with my little gravitational lens | The

In the new image, the full-scale distribution of vast clumps of dark matter can be seen around galaxy clusters, connected by wispy filaments of dark matter and trailing off to enormous voids where no matter exists.

BBC: Dark matter hints in widest-yet view of dark mystery