JUST A SHORT BLOGPOST WITH SOME SIMPLIFIED QUESTIONS, PERSONAL CURIOSITY :
YESTERDAY I HAD TO CHANGE THE BATTERIES OF AN (OLDER MODEL) PERSONAL WEIGHING SCALE OF A CLOSE RELATIVE, SO WHEN I WANTED TO PUT THE NEW BATTERIES I SAW AT THE BACK OF THE SCALE THIS IMAGE OF A' WORLD ZONE MAP' AND NEXT TO IT A BUTTON WHICH CAN BE PLACED AT THE ZONE IN WHICH YOU'RE USING THE SCALE:
IMAGES:
(PHILIPS HF 8000/00, UNAVAILABLE NOWADAYS : "WITH THE SIX CLIMATE DEGREE( LINK WITH GRAVITY?) ZONES OF THE EARTH TO ADAPT THE SCALE TO THE CORRECT CLIMATE ZONE" https://www.philips.nl/c-p/HF8000_00/digitale-weegschaal)
Gravity map reveals Earth's extremes
By Jacob Aron
19 August 2013
Go to Mount Everest (middle) if you want to lose weight
(Image: GGMplus/Curtin University)
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.
Gravity is often assumed to be the same everywhere on Earth, but it varies because the planet is not perfectly spherical or uniformly dense. 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.
NASA and the European Space Agency both have satellites with highly sensitive accelerometers that map the planet’s gravitational field, but these are only accurate to within a few kilometres. Adding in topographical data, which adjusts for height variations in local terrain, can improve the maps’ resolution. Accurately constructing tunnels, dams and even tall buildings requires knowledge of the local gravity to guide GPS measurements of height, so higher resolution maps are important for civil engineering.
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 consists of more than 3 billion points, with a resolution of about 250 metres. Computing gravity at five points would take 1 second on an ordinary PC, but the team used a supercomputer to do the whole lot in three weeks.
Free fall favourite
The model pinpoints more extreme differences in gravitational acceleration than previously seen. Standard models predict a minimum gravitational acceleration of 9.7803 metres per second squared at the equator and 9.8322 m/s2 at the poles. Hirt’s model pinpoints unexpected locations with more extreme differences. Mount Nevado Huascarán in Peru has the lowest gravitational acceleration, at 9.7639 m/s2, while the highest is at the surface of the Arctic Ocean, at 9.8337 m/s2.
“Nevado was a bit surprising because it is about 1000 kilometres south of the equator,” says Hirt. “The increase in gravity away from the equator is more than compensated by the effect of the mountain’s height and local anomalies.”
These differences mean that in the unlikely event that you found yourself falling from a height of 100 metres at each point, you would hit the surface in Peru about 16 milliseconds later than in the Arctic. You would also lose 1 per cent of your body weight in moving from the Arctic to the Peruvian mountaintop, although your mass would not change.
Journal reference: Geophysical Research Letters, DOI: 10.1002/grl.50838
