Gravity-measuring smartphone tech might save you from a volcano

Gravity-measuring smartphone t...
The prototype mini gravimeter, known as the Wee-g
The prototype mini gravimeter, known as the Wee-g
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The prototype mini gravimeter, known as the Wee-g
The prototype mini gravimeter, known as the Wee-g

Although you may not use a gravimeter to detect tiny changes in gravity (or for anything else), they are commonly used in fields such as oil exploration and environmental surveying. They could have more applications, were it not for the fact that they tend to be relatively large and expensive. Scientists at the University of Glasgow have set about addressing that limitation, by creating a compact gravimeter that incorporates smartphone technology.

Called the Wee-g, the prototype device utilizes the same micro-electromechanical systems (MEMS) that are manufactured for use in phones' accelerometers.

Whereas phone systems include "relatively stiff and insensitive" springs for maintaining orientation, however, the Wee-g incorporates a silicon spring which is 10 times thinner than a human hair. Combined with a 12-mm-square sensor, that added sensitivity allows the gravimeter to pick up even the most minute changes in the Earth's gravitational field.

To test the device, the researchers placed it in a basement room in the university, then used it to measure "Earth tides" – these are slight expansions and contractions of the Earth's crust, as caused by the gravitational pull of the Sun and Moon. Readings taken over a seven-day period from the Wee-g were consistent with mathematical models, which in turn have been shown to be an accurate measure of the tides.

"There are a lot of potential industrial applications for gravimeters, but their cost and bulkiness have made them impractical in many situations," says researcher Richard Middlemiss. "Wee-g opens up the possibility of making gravity measurement a much more realistic proposition for all kinds of industries: gravity surveys for geophysical exploration could be carried out with drones instead of planes; and networks of MEMS gravimeters could be places around volcanoes to monitor the intrusion of magma that occurs before an eruption – acting as an early warning system."

The scientists are now working on making the device even smaller, and are pursuing commercialization with industry partners.

Source: University of Glasgow

Gravity meters that function dynamically (in a UAV, on an airplane...) are usually way more complicated than ones that are static (sitting on the ground). They have to compensate for translation and rotation of the vehicle, and possibly pressure, temperature, and magnetic fields. I was expecting a MEMS device to eventually put me out of a job (designing and building dynamic gravity meters). This article tells me Wee-g will be a good/cheap static meter but it may or may not be work as a dynamic meter.
Mel Tisdale
Justincase's very informative comment not withstanding, I wonder if these devices could somehow be put to use in detecting ballistic missile submarines as they patrol supposedly invisible to their enemy. They are massive and one suspects must affect such devices to a degree. At least the possibility should impact on the minds of those responsible for such matters.
As the old prospector said, "there's gold in them thar hills". I want one of these meters to find the really rich ore beds. Forget drilling and cores.