Force
Forces and Motion

Losing weight the Canadian way

Stories from Physics for 11-14 14-16 IOP RESOURCES

The GRACE satellites, (see also page 6), use microwave beams to measure tiny changes to distributions of mass in the Earth. The satellites have been used to investigate a gravitational anomaly, the relatively low gravitational field around the Hudson Bay in northeast Canada. The effect is hypothesised to arise from two possible causes: the rebounding of the Earth’s crust in the area following the melting of glaciers, or the motion of the crust due to convection currents in the mantle. Unfortunately, the effect of the anomaly on your weight will be small — the phenomenon leads to a reduction in the gravitational field strength of around 0.005%.

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