Daniel Winester, seated, and Franek Hasiuk, standing, set up a gravimeter inside the Christian Petersen Art Museum on June 21. Winester, of the National Geodetic Survey, set the instrument over a brass gravity mark a crew set in the museum floor last summer. The mark allows researchers to do any follow-up studies at the same spot. Over the course of 24 hours, the nearly $2 million instrument measures a place's absolute gravity. Hasiuk, an assistant professor of geological and atmospheric sciences, says gravity varies depending on your distance from the Earth's center and the material underground. He has an explanation here. Larger image. Photo by Mike Krapfl.