The University of Glasgow physicists have developed a smaller, lighter, and cheaper device that measures the Earth’s gravity. The device can be set up in a drone aircraft and can even be used to monitor volcanoes and look for oil.
Gravimeters measures the Earth’s gravity and can be used to determine magma movements which happens before a volcanic eruption. The smallest gravimeters on the market weigh several kilogrammes and can cost up to US$100,000 (AU$130,651).
This size and price issues are now solved by the new device. Moreover, it uses a microelectromechanical system (MEMS) like the one found in smartphones but is 1,000 times more sensitive to accelerations.
They sliced a 15-millimeter by 15-millimeter by 7-micrometre piece of silicon and placed this rectangular central mass to a square frame with three springs. The frame hangs between a white LED and a photodiode to measure the position of the mass so when the gravity causes it to move, a light is shone onto the mass, casting a shadow on a detector behind the mass.
The researchers ran the gravimeter for several days to measure the Earth tides and movements of the crust as a result of the gravitational pull of the sun and moon. When the crust moved up and down by up to 40 centimetres, this gravity changes also and moved the mass by up to 16 nanometres. The team says that the device is also capable of detecting oil with a volume of 50 m3 at 150 metres underground.
Richard Middlemiss, the device’s creator, points out that this device cannot measure gravitational waves. Gravitational waves are ripples in spacetime caused by the most energetic and violent mechanisms in the universe.
Nevertheless, Open University’s volcanologist Hazel Rymer says, “It is just so exciting,” she told BBC Inside Science. “It’s an absolute game-changer. Not yet – it’s still something that needs to be operated in the laboratory and they’ve got to attach it very firmly to the floor. But the point is, they’ve now got a sensor that is sensitive enough to measure the types of gravity changes that I’m interested in – and anybody else that is using gravity meters.”
Physicist Giles Hammond says that the team is planning to create a portable gravimeter to be tested in the field. They also plan to make the device work in 3D.