06 March 2013
Join our national experiment
A national physics experiment that everyone can participate in is being coordinated by an RMIT University academic.
Associate Professor Greentree with Albert Park College Melbourne year nine students Emma Rossignol, Luke Patitsas and Erika Palomares and Professor Schmidt.
Associate Professor Andrew Greentree, a Vice-Chancellor's Senior Fellow in the School of Applied Sciences, helped launch the project with year nine students at the Albert Park College in Melbourne last Friday with Australia's 2011 physics Nobel Laureate, Professor Brian Schmidt.
Associate Professor Greentree is a Special Project Officer for the Australian Institute of Physics, which supports professional physicists and promotes all aspects of physics to the wider community.
The experiment allows school students and the public to follow in Galileo's footsteps and measure local gravity.
"They'll measure the weight of the Earth, and discover that your weight changes (just a little) as you travel around Australia," Associate Professor Greentree said.
"The students at Albert Park College were introduced to the experiment first performed by Galileo, and they made the first contributions to a new map.
"Over the year, the Australian Institute of Physics hopes to involve thousands of people around the country."
Associate Professor Greentree said the experiment was called 'The BIG little g project' and was open to people around Australia.
"All you need is a home-made pendulum, a tape measure and a stop watch," he said.
"Little g is physics shorthand for the local gravitational field, or how much the Earth pulls (accelerates) objects including people towards it."
While watching a swinging chandelier, Galileo realised that it kept time very accurately. The same applies to any pendulum.
But the time it takes to swing from side to side depends, not on the weight of the pendulum, but on the length of its cord and on acceleration due to the Earth's gravitational field ('little g') at that spot.
Associate Professor Greentree said the experiment would show that the strength of the Earth's gravitational field varied from place to place.
"Local gravity depends on the 'weight' of the Earth at that point due to latitude, altitude and local geology," he said.
"These variations can be used to find underground minerals or water, and to measure shrinking polar ice caps."
Associate Professor Greentree will compile the data to build a map of Australia's gravitational field that in some areas will be more sensitive than current maps.
"The most sensitive maps of little g are made with NASA satellites," he said.
"They get down to a resolution of around 100km, but we'd like to measure Earth's gravitational field to resolutions of around 100m where we can get lots of results coming in.
"The more citizen scientists we attract, the more accurate the map.
"We want to make this one of the biggest physics experiments ever conducted, in terms of the number of participants.
"We're inviting primary and secondary school children and the general public to make a simple pendulum, do the test and submit their results online."
Albert Park College Melbourne year nine students with their teacher and visitors.
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