Science Night at Eastbrook Makerspace
1Every month the Eastbrook Makerspace holds a science night where members build and test simple devices. This month the theme was gravity. Volunteer engineer Elias Varga brought a wooden model of a famous device called a torsion balance. In 1798 the scientist Henry Cavendish hung a rod with a small lead ball on each end from a thin wire. He then placed two large lead balls, each about 160 kg, near the small ones. Over several minutes the small balls swung slowly toward the large balls and twisted the wire a tiny amount. By measuring the twist, Cavendish worked out the size of the force between the balls.
2The makerspace model is only for display. The real effect is so small that air currents, a slammed door or footsteps on the floor can hide it. So eighth grader Noor Castellanos ran a gravity simulator on a laptop instead. She placed two solid lead spheres, A and B, so that their centers were always 1.00 m apart. In each trial she changed the mass of one or both spheres and recorded the gravitational force between them in micronewtons (µN). One micronewton is one millionth of a newton. For comparison, a single sheet of printer paper weighs about 50,000 µN.
3In every trial the simulator drew two force arrows: one on sphere A pointing toward sphere B, and one on sphere B pointing toward sphere A. The two arrows were always the same length. Noor did not get to finish trial 6 before the laptop battery died, so that row is still blank.
4Elias added two facts from space science. Earth's mass is about 81 times the mass of the Moon, and Jupiter's mass is about 318 times the mass of Earth. When a space probe flies past a large planet, the planet pulls it inward, and the probe's path bends toward the planet before it moves away again.