Weighing a new option - Macleans.ca

Weighing a new option

Canadian researchers are looking to change the way things are measured


Weighing a new optionAs with so many yo-yo dieters, the weight of a kilogram is constantly in flux—at least at an atomic level. But Ottawa researchers are hoping to get the kilo’s waistline permanently in check by changing how it’s measured.

The kilogram is currently defined by the International Prototype Kilogram, a golf-ball-sized cylindrical weight made out of platinum alloy. Because a kilogram is a physical object, it constantly releases and collects atomic particles, meaning its mass—and the mass of all kilograms—is always changing. ““If [the IPK] moves up or down the others have to follow,” says Barry Wood of the National Research Council in Ottawa. “It’s totally artificial.”

Wood and his team are heading up a movement to measure kilograms against the charge of an electron, a natural constant, using a type of specialized motor called the watt balance. “You can lift mass with a motor,” he says. “If I know how much current I’m putting into the motor, that tells me details about how much I’ve lifted.” Since the NRC purchased the watt balance (pictured below) from the British government two years ago, Wood has been using the room-sized metal machine to determine exactly how much current is needed to lift a kilogram. The data, which has so far cost $2.5 million to collect, is compared to two other watt balances in the U.S. and Switzerland, and used to calibrate the devices to make their results consistent.

Wood estimates this will take about four years, and then the International Bureau of Weights and Measures will redefine the kilogram using the electric standard. It won’t mean much for dieters, but will have a big impact on the scientific community. “This new process will stay the same for the next thousand, million years,” says Wood. “That’s a characteristic we value.”