Gravity is often assumed to be the same everywhere on Earth, but it varies because the planet is not
perfectly spherical or uniformly dense.
Want to lose weight fast? No need to adjust your diet - just move to higher ground. This weight change is
the result of fluctuations in Earth's gravity, which a new high-resolution map shows are greater than thought,
In addition, gravity is weaker at the equator due to centrifugal forces produced by the planet's rotation.
It's also weaker at higher altitudes, further from Earth's centre, such as at the summit of Mount Everest.
Gravity map shows weakest gravity at summit of Mount Everest (middle). Credit: GGMplus/Curtin University
Their work is the first-of-its-kind to model gravity at unprecedented fine scales yet with near-global coverage.
The new models are beneficial for a wide range of scientific and engineering applications and freely available
to the public.
Christian Hirt of Curtin University in Perth, Western Australia, and
colleagues combined gravity data from satellites and topographic data to map gravity changes between latitudes
60° north and 60° south, covering 80 per cent of Earth's land masses.
The map - that pinpoints unexpected locations with more extreme differences - consists of more than 3 billion
points, with a resolution of about 250 meters.
Mount Nevado Huascaran in Peru, for example, has the lowest gravitational acceleration on the planet while
the highest is at the surface of the Arctic Ocean.
"Nevado was a bit surprising because it is about 1,000 kilometers [620 miles] south of the equator,"
research leader Christian Hirt said.
"The increase in gravity away from the equator is more than compensated by the effect of the mountain's height
and local anomalies."
High resolution gravity maps are important for civil engineering because accurately
constructing tunnels, dams and even tall buildings requires knowledge of the local gravity to guide GPS
measurements of height.