The Dark Side of the Cosmos

As astronomers struggle to illuminate the nature of dark matter, a new report hints that as much as 97% of the universe could be made of the mystery stuff

WHEN CHARLES ALCOCK PEERS UP at the nighttime sky, he wonders not at the luminous stars but at the blackness that enfolds them. The Milky Way, Alcock knows, is like a sprinkling of bright sequins on an invisible cloak spread across the vastness of space. This cloak is woven out of mysterious stuff called dark matter because it emits no discernible light. A sort of shadow with substance, dark matter dominates the universe, accounting for more than 90% of its total mass. Yet scientists, struggling to interpret just a few sparse clues, know virtually nothing about it. The dark matter could...

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