Embedded in darkness (economist)

MOST of reality appears to be missing. Physicists reckon that the missing matter must be there, but that it is dark. Finding the stuff is damned tricky because dark matter, by definition, cannot be seen. So some of those physicists have been busy trying to devise ways of glimpsing it indirectly—and two groups of them now think their methods are ready to test.

One reason to believe dark matter exists is that galaxies rotate at such speeds that they would fly apart without it, or so the argument goes. The fact that galaxies persist suggests they are held together by the gravitational pull of something invisible—in other words, dark matter. This stops stars being shed from their edges.

Read complete article here. {via economist}