Snaring a dark energy 'chameleon': Is dark energy hiding from us? Matter may be screening it from our view

f dark energy is hiding in our midst in the form of hypothetical particles called "chameleons," Holger Müller and his team at the University of California, Berkeley, plan to flush them out.

The results of an experiment reported in this week's issue of Science narrows the search for chameleons a thousand times compared to previous tests, and Müller, an assistant professor of physics, hopes that his next experiment will either expose chameleons or similar ultralight particles as the real dark energy, or prove they were a will-o'-the-wisp after all.