Honey, I Misplaced the Universe

Science can't find 90% of the cosmos. This "missing mass" problem may hold clues to the Big Bang and to the plane of the spirit.

People lose their car keys and insurance cards, and any one of a pair of socks can vanish as surely as if it had been sucked into another dimension. But lose most of the universe? Now there's a feat--and one that has been accomplished. Preposterous as this sounds, astronomers and cosmologists are in wide agreement that most of the universe is missing. The latest physics may suggest where the missing parts of the universe are and in turn provide some hints about much larger questions--including whether there is an ethereal reality all around us.

Here's why scientists think most of the cosmos is missing: The heavens behave as though being acted on by far more material than meets the eye. For instance, when cosmologists "weigh" the universe by estimating the mass of the components that shine, and thus are easy to detect (mainly, stars and nebulae), it appears the galaxies don't contain anywhere near the amount of matter necessary to keep them from flying apart. Galaxies spin like disks, and stars on the outer rim of our Milky Way are whirling with so much speed and momentum, they ought to overcome the galaxy's gravity and soar off into the interstellar void. Yet they don't; the heavens remain ordered. This causes cosmologists to assume that there must be an enormous amount of "missing mass," undetected material that keeps the universe stable. Current estimates hold that in order for the universe to behave the way it does, visible matter can make up only 10% to a third of the firmament. The rest of the universe, two-thirds to as much as 90%, is "missing."


Where or what is the missing mass? It's probably not in black holes. For techno-reasons that can be skipped here, even though black holes are the most massive objects that can be imagined, they probably do not account for the missing substance. The leading theory is, instead, that the universe is rife with an unknown "dark matter" or even "dark energy." Not dark as in the Dark Side--"dark" in this usage means "We don't see it." But there could well be a mystical implication, which we'll return to in a moment.

What might dark matter be? The first credible theory was "brown dwarfs." This idea held that each galaxy contains many billions of objects similar to the planet Jupiter--very large by the standard of planets, but not large enough to ignite into stars. If brown dwarfs were everywhere, astronomers would have a hard time finding them because these objects would not shine, but they might account for the missing mass. Recently, the brown-dwarf theory has fallen on hard times, mainly because the material for brown dwarfs would have to come from supernovae, and there don't seem to have been enough of these explosions in cosmic history to generate the required ingredients.

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Gregg Easterbrook
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