Galileo’s famous gravity experiment holds up, even with individual atoms
Different types of atoms fall with the same acceleration due to gravity
According to legend, Galileo dropped weights off of the Leaning Tower of Pisa, showing that gravity causes objects of different masses to fall with the same acceleration. In recent years, researchers have taken to replicating this test in a way that the Italian scientist probably never envisioned — by dropping atoms.
A new study describes the most sensitive atom-drop test so far and shows that Galileo’s gravity experiment still holds up — even for individual atoms. Two different types of atoms had the same acceleration within about a part per trillion, or 0.0000000001 percent, physicists report in a paper in press in Physical Review Letters.
Compared with a previous atom-drop test, the new research is a thousand times as sensitive. “It represents a leap forward,” says physicist Guglielmo Tino of the University of Florence, who was not involved with the new study.
Researchers compared rubidium atoms of two different isotopes, atoms that contain different numbers of neutrons in their nuclei. The team launched clouds of these atoms about 8.6 meters high in a tube under vacuum. As the atoms rose and fell, both varieties accelerated at essentially the same rate, the researchers found.