University physicists recently developed a new method for making precise measurements of gravity in small spaces, potentially allowing for the creation of new devices with more commercial applications.
Assoc. Physics Prof. Cass Sackett, the project’s principal investigator, said the new method, like older ones, is based on using the time it takes for an object to drop to measure the acceleration caused by gravity.
In this experiment, rubidium atoms were cooled to the point of being almost motionless, Sackett said. Afterwards, these atoms were dropped in a small space, and lasers were shined on them to give them an “extremely precise kick,” Sackett said.
Because of the easily measurable force these lasers can apply, Sackett noted, the method is equitable to measurements about as accurate as those achieved in introductory, college-level physics labs, although it cannot yet go further. He noted, however, that the technique has the potential to become much more accurate and that it has some benefits compared to older procedures.
“The nice thing about this method is it only requires 10 to 20 [micrometers] of vertical space, so a practical device can be made very small,” said Graduate Engineering alumnus Jeramy Hughes, who worked on the experiment prior to his graduation.
Hughes said previously existing methods, which involved dropping atoms without the use of lasers, required at least 10 centimeters of space, with some instruments measuring a meter tall to obtain a greater degree of accuracy. By using lasers to bounce the atoms more than a hundred times, however, the new technique has been able to replicate some of the accuracy of older techniques, and in a much more practical amount of space.
Very accurate measurements of gravity could be useful in various fields, including navigation, oil exploration, the search for underground caves and even the discovery of smuggled cargo, Sackett said. Devices designed to take advantage of the new method researched at the University could detect the small effects that individual objects or places — such as oil or iron fields — have on the Earth’s gravity, allowing scientists, researchers and commercial prospectors to find resources easily without the need of larger, bulkier measuring tools. In this respect, the new technique will enable the creation of devices small enough to be conveniently used on the airplanes, boats, submarines and other vehicles needed for such applications, Sackett said.
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