FREE-FALLIN’
Galileo’s most famous experiment has taken a trip to outer space. The result? Einstein was right yet again. The experiment confirms a tenet of Einstein’s theory of gravity with greater precision than ever before.
According to science lore, Galileo dropped two balls from the Leaning Tower of Pisa to show that they fell at the same rate no matter their composition. Although it seems unlikely that Galileo actually carried out this experiment, scientists have performed a similar, but much more sensitive experiment in a satellite orbiting Earth. Two hollow cylinders within the satellite fell at the same rate over 120 orbits, or about eight days’ worth of free-fall time, researchers with the MICROSCOPE experiment report December 4 in Physical Review Letters. The cylinders’ accelerations match within two-trillionths of a percent.
The result confirms a foundation of Einstein’s general theory of relativity known as the equivalence principle. That principle states that an object’s inertial mass, which sets the amount of force needed to accelerate it, is equal to its gravitational mass, which determines how the object responds to a gravitational field. As a result, items fall at the same rate — at least in a vacuum, where air resistance is eliminated — even if they have different masses or are made of different materials.
The result is “fantastic,” says physicist Stephan Schlamminger of OTH Regensburg in Germany who was not involved with the research. “It’s just great to have a more precise measurement of the equivalence…
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