In a remarkable new paper in the journal Nature, researchers from the University of Vienna show how they measured the gravitational pull of a 2-mm gold sphere weighing just 90 milligrams. This was accomplished by using lasers to carefully measure how the effects of the sphere’s gravity changed the swinging of a tiny pendulum of glass, four centimeters long and half a millimeter thick, capped with gold balls, and suspended from a glass fiber a few thousandths of a millimeter in diameter. 

According to co-author Jeremias Pfaff: We move the gold sphere back and forth, creating a gravitational field that changes over time. This causes the torsion pendulum to oscillate at that particular excitation frequency. 

These gold balls are roughly the mass of a ladybug! This experiment shows that it may one day be possible to measure traces of dark matter and dark energy by how they affect the gravitational field. Study lead author Tobias Westphal puts it this way: According to Einstein, the gravitational force is a consequence of the fact that masses bend spacetime in which other masses move. So what we are actually measuring here is, how a ladybug warps space-time. 

And let’s face it, that is just kind of cool.

More Information

Universität Wien press release

“Measurement of gravitational coupling between millimetre-sized masses,” Tobias Westphal et al., 2021 March 10, Nature