DARK matter has a dark secret: it has had long-term dealings with visible matter.
Theory predicts that the proportion of visible to dark matter should increase with time, so François Hammer, an astronomer at the Paris Observatory in France, and his colleagues used the Very Large Telescope at Cerro Paranal in Chile to examine 32 young galaxies 6 billion light years away. They compared the mass ratio of visible and dark matter in these galaxies with the ratio in galaxies that are close by – and therefore older. Surprisingly, the ratio was about the same in both young and old…
