For decades, astronomers have grappled with their inability to decipher the universe’s darkest secret: the identity of most of its matter.
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It’s not the same stuff as the ordinary atomic variety of matter common on Earth. Atoms or their parts — such as protons and neutrons — make up less than 17 percent of the mass in the cosmos. All the rest is “dark” — invisible to eyes and telescopes, its presence deduced by its gravitational tug on stars and galaxies (SN: 8/28/10, p. 22). This mystery matter apparently consists of tiny particles of some exotic species, but efforts to trap them (in underground detectors) or make them (in particle accelerators) have produced frustrating results: Some experiments find hints of such particles; others find nothing.
Yet despite the frustration, physicists offer a message of hope. With a deluge of new data already in hand, and more precise probes in the works, learning the identity of dark matter may just be a matter of time.