A look at dark matter

Dark matter -- a long-postulated mystery substance that makes up at least 6/7 of the mass of the universe -- has apparently finally been found.

One of the greatest mysteries of the universe is about to be unravelled with the first detailed, three-dimensional map of dark matter - the invisible material that makes up most of the cosmos.

Astronomers announced yesterday that they have achieved the apparently impossible task of creating a picture of something that has defied every attempt to detect it since its existence was first postulated in 1933.

Dark matter is thought to be some sort of subatomic particle that doesn't interact much with ordinary matter like you and me. Think of neutrinos with mass. Because it doesn't interact directly, the only way to detect its presence is by the gravitational effect of its mass.

Even more interesting is how the dark matter is organized:

"A filamentary web of dark matter is threaded through the entire universe, and acts as scaffolding within which the ordinary matter - including stars, galaxies and planets - can later be built," Dr Massey said. "The most surprising aspect of our map is how unsurprising it is. Overall, we seem to understand really well what happens during the formation of structure and the evolution of the universe," he said.

Astronomers have long been aware of various structural symmetries in the visible universe. For instance, they've identified a "supercluster" known as the Great Wall, a sheet of galaxies 500 million light years long, 200 million light years wide and 15 million light years deep. Another is the Great Attractor.

Such structures are exceptions to theory, which expects a more uniform distribution of galaxies resulting from the Big Bang. Dark matter, it turns out, may be one reason such structures exist.

Cool stuff. And one reason why generous funding of space exploration (manned, robotic and telescopic) should continue.

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