Maybe the real secret to weight loss is moving to the tundra?
Around Canada’s Hudson Bay region, far to the north-east, researchers in the 1960s discovered that everything weighed only slightly less.
In an area of more than 500,000 square miles you lose about 1/25,000 of your body weight.
Scientists first discovered this anomaly in the 1960s when they first mapped variations in Earth’s gravitational field. But it took decades for them to understand why.
The cause? Reduced molten magma beneath the region’s surface, squeezed out by surface pressure from two huge glaciers during the last Ice Age.
This map of Earth’s gravity field, released on July 30, 2003 based on a joint mission by NASA and the German Aerospace Center Gravity Recovery and Climate Experiment (GRACE), shows in deep blue the unusual gravity anomaly around the saline Northeast Hudson Bay of Canada
Many polar bears live around the ice rivers and sandy beaches of Hudson Bay. Each bear weighs just a little less, about 1/25,000 of what it would weigh in any other zoo
Say you weigh 150 pounds. Near Hudson Bay, the scale would read about 149,994 pounds.
The simple answer to this puzzle begins with the fact that the gravitational pull that one object exerts on another is directly proportional to its mass.
But since an object entering Hudson Bay doesn’t necessarily lose mass along the way, that doesn’t explain the mystery of Canada’s “lack of” gravity.
To solve this problem, the researchers turned to NASA’s twin Gravity Recovery and Climate Experiment (GRACE) satellites, which they used in 2007 to map two gravity anomalies around Canada’s Great Saltwater Bay and show how those anomalies change over time.
“The Canadian anomaly has been known for a long time and is the result of crustal deformation during the last ice age,” physicist Dan Britt, director of the Center for Lunar and Asteroid Surface Science at the University of Central Florida, told the DailyMail. com via email.
At that time, about 20,000 years ago, Canada and much of North America lay in cold storage beneath the Laurentide Ice Sheet, a vast glacier about two miles thick near Hudson Bay.
“A few miles of ice is heavy enough to dent the crust,” said Britt, whose own work has occasionally involved fine-tuning lunar gravity models based on the geological differences between different types of lunar rock.
“The same process is happening in different places where there were thick layers of ice,” Britt said.
“The details are related to the viscosity of the mantle.”
Under the crushing weight of the Laurentide Ice Sheet, the Earth’s crust around Hudson Bay began to compress and sink.
In doing so, it displaced some of the hot magma from the semi-liquid mantle beneath, like a crushed sandwich displacing peanut butter and jelly.
This compression was strongest on either side of Hudson Bay, where two huge domes had formed on the ice sheet.
The gradual retreat of the Laurentide River over the next 10,000 years was responsible for the formation of many North American landmarks, including the Great Lakes.
Some theorists predicted that all that displaced molten mass would have reduced Earth’s gravitational pull around Hudson Bay – but NASA’s GRACE satellites showed that was only part of the story.
While the Laurentide ice sheet theory and GRACE data explain some of the reasons for the lack of gravity over Canada, they only explain about 25–45 percent of the gravitational difference.
Scientists estimate that the remaining 55-75 percent stems from a theory related to convention.
Far below the earth’s surface, a layer of molten rock known as magma creates convection currents due to the natural rise and fall of the bubbling substance.
This pulls the Earth’s tectonic plates inward, causing the mass and gravity of the Hudson Bay area to decrease.
Gravity is forecast to return to Canada, but gradually.
Geophysicist Mark Tamisiea of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, told Science magazine that it will take up to 300,000 years for the regions gravity to equal the global average.
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