Smallest-Ever Gravitational Force Measured with Tiny Ball

Here’s a Snapple-cap factoid that’d be fun to whip out in conversation: on a planet the size of a ladybug, objects would fall 30 billion times slower than they do here on Earth. And how do scientists know this absurdly esoteric fact? Because they just measured the smallest amount of gravitational force ever. And it emanated from tiny gold balls that only weigh about .0002 pounds. Or as much as a ladybug.

Science News reported on the new measurement, which a team of researchers at the University of Vienna described in a recent study. In the study, published in the journal Nature, the researchers say their goal was to better understand the characteristics of the gravitational force on a micro scale; as opposed to a macro scale, which is far more common. (Think celestial objects like stars, black holes, etc.)

Smallest-Ever Gravitational Force Measured with Tiny Ball_1

Tobias Westphal/Arkitek Scientific

To measure the miniscule amount of gravitational force, the researchers opted for tiny gold balls with .08-inch wide diameters. For the experiment, they built a miniature version of the contraption at the heart of a famous experiment from the late 18th century, in which scientist Henry Cavendish measured the gravitational pull of two 2-inch-wide, 1.6-pound lead balls using a torsion pendulum; that is, a device in which two masses are placed at the end of a wooden rod, which itself is suspended from a thin wire that can rotate freely.

In Cavendish’s experiment, he used the torsion pendulum to measure the gravitational constant. He did so by measuring the twisting force applied to the wire as the balls were attracted to other balls; themselves kept in place thanks to their own suspension. In this experiment, the researchers took the two micro-balls and placed them on the ends of a glass rod; itself suspended from a super-thin glass wire with a diameter just a few thousandths of a millimeter thick. Then performed the same experiment.

Scientists have measured the smallest amount of gravitational force ever using ultra-tiny gold balls.

Tobias Westphal/Arkitek Scientific

“We move the gold ball back and forth, creating a gravitational field that changes over time,” Jeremias Pfaff, one of the researchers involved in the experiment, said in a press release. “This means that the torsion pendulum also oscillates at this particular excitation frequency,” the researcher added.

As for next steps, the researchers want to measure the mass of something a thousand times lighter than these balls. These kinds of measurements, the researchers say, will open up the field of gravitational physics. And potentially offer traces of dark matter or dark energy; two discoveries that would enlighten the formation of the universe, and all the planets, stars, and tiny balls inside it.