In a Sudbury mine, physicists probe secrets of dark matter – by Kate Allen (Toronto Star – December 6, 2015)

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SUDBURY, ONT.—In a hot, dark cavern buried two kilometres below the earth’s surface, a pallet of No Name dog food lies covered in dust.

These subterranean passageways have certainly seen stranger sights than bulk dog food. There was the one-of-a-kind sanding robot, for starters. There was the giant acrylic orb, split in two pieces to fit down the mine’s narrow elevator shaft. Over the next four weeks, there will be 3.6 tonnes of liquid argon.

Every day, a parade of physicists in coveralls and head lamps rattles down the elevator and tramps through these passages — plus engineers, welders, machinists, grad students, the occasional journalist. Stephen Hawking was here.

But to grasp the scale and ambition of what’s happening at SNOLAB, it helps to think about that pallet of dog food.

The scientists down here are building a massive experiment, DEAP-3600, designed to capture faint signals from dark matter, one of the greatest unresolved mysteries in physics. Whatever dark matter is, it accounts for the vast majority of the matter in the universe.

Physicists have described the ordinary, visible matter we know — galaxies, comets, planets, us — as the froth on top of a deep, dark ocean. But we don’t know what that ocean is made of. Dark matter is invisible: its existence is inferred, never seen.

At SNOLAB, scientists want to change that. They are building the world’s most sensitive dark matter detector of its kind, going to painstaking lengths — burying the lab in an ore mine in Sudbury, for instance — to avoid anything that might mask a signal.

An experiment of this scale is a scientific feat involving 65 researchers at 10 institutions in three countries. It is also a logistical nightmare.

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