Law of Gravity Tested with 2mm Gold Ball

Even the smallest of objects obey the law of gravity. A gold ball just 2 mm wide is now the smallest object to have its gravitational pull measured. Its mass is about 90 milligrams, and observations are being made on how it behaves in gravity. The gold sphere tugging on another similarly-sized sphere confirms that gravity acts the same as expected, even for the fragile gravitational fields. Physicists reported in the March 11 Nature about the same.

The previous experiments have had objects with masses of hundreds of milligrams or more. Newton’s law of universal gravitation states, “The gravitational force between two masses is inversely proportional to the square of the distance between them.” The two objects will pull one another with one-quarter strength.

A team of physicists from Vienna tested the relationship between the tiny masses. The researchers attached a gold ball to a horizontally suspended beam that could rotate freely in response to another golden sphere’s gravitational force. According to Newton’s law predictions and of Einstein’s general theory of relativity, the results matched. Both these theories are equivalent under most everyday conditions.

The ultimate goal of researchers is to test how gravity behaves on far smaller scales. They want to test how it works for objects so minuscule that they can perform quantum feats like existing in multiple places simultaneously. To follow the quantum rules, the gold spheres are too large. However, the experiment takes scientists a small step closer to exploring the quantum side of gravity.