Dark Matter and the Shadow Universe

A preview by our editor in chief of the June issue of

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Given the inky blackness of space, I suppose it shouldn't have been surprising that we can't detect the parts of the cosmos that do not glow like the stars or radiate other types of energy. Cosmologists, observing galaxies rotating at speeds too fast to be possible given those observable components, have hypothesized unseen particles called dark matter.

What is it doing, and what is its composition? In “,” Bogdan A. Dobrescu and Don Lincoln delve into the complexity of this unseen universe. Dark matter could contain a world of particles. Dark atoms and molecules could perhaps clump together into galactic disks that overlap with the ordinary matter disks and spiral arms of galaxies such as Andromeda. Experiments are under way with the aim of detecting such complex dark matter. “The real message,” Dobrescu and Lincoln write, “is that we have a mystery before us and that we do not know what the answer will be.”

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