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The Fifth Force of Physics Is Hanging by a Thread - Issue 46: Balance

The Fifth Force of Physics Is Hanging by a Thread - Issue 46: Balance Read full article

16 March 2017, 7:00 am

How about that! Mr. Galileo was correct in his findings.” That conclusion wasn’t based on the most careful experiment you’ll ever see, but it was one of the most spectacular in its way—because it was performed on the moon.

In 1971, Apollo 15 astronaut David Scott dropped a feather and a hammer from the same height and found that they hit the lunar surface at the same time. The acceleration due to gravity doesn’t depend on a body’s mass or composition, just as Galileo asserted from his (probably apocryphal) experiment on the Leaning Tower of Pisa.

In Galileo’s Dreams: A moon-bound reprise of Galileo’s famous experiment from the leaning tower of Pisa. Nikolas Zane

Or does it? Jump forward to the front-page headline of The New York Times in January 1986: “Hints of 5th Force in the Universe Challenge Galileo’s Findings.” The newspaper was reporting on a paper in the premier physics journal Physical Review Letters by physicist Ephraim Fischbach and his colleagues, describing evidence that the acceleration due to gravity does vary depending on the chemical composition of the object in question. Gravity, it seemed, was not quite what we thought it was: its effects are modified by what the…
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