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Q & A: Measurement of the gravitational constant G

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Most recent answer: 12/20/2014
How is the universal gravitational constant measured and proven to be universal?
- Eduardo (age 40)
MO, Uruguay

Hello Eduardo,

It's a tough measurement because G is so small.  Nevertheless Henry Cavendish managed to measure it in 1797 to within 1% of the currently accepted value.  He used a torsion ballance .  See .  Modern experiments are usually refined variations of Cavendish's.

As to its universality, Galileo is said to have shown in 1589 that it was independent of the mass of an object by dopping two balls of different weight from the Leaning Tower of Pisa:  they both arrived at the ground at the same time.  Its constancy in time can be checked by astronomers observing the kinematics of distant galaxies.



(published on 12/20/2014)

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