Cavendish's torsion-bar experiment HD

The experiment was performed in 179798 by the English scientist Henry Cavendish. He followed a method prescribed and used apparatus built by his countryman, the geologist John Michell, who had died in 1793. The apparatus employed was a torsion balance, essentially a stretched wire supporting spherical weights. Attraction between pairs of weights caused the wire to twist slightly, which thus allowed the first calculation of the value of the gravitational constant G. The experiment was popularly known as weighing the Earth because determination of G permitted calculation of the Earth's mass.

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• Cavendish
• torsion-bar
• gravitation
• mechanics
• physics
• animations
• Earth

[qed100]

Excellent question. The masses are chosen for their chemical compositions. They should be as dense as possible (to allow their centers of mass to approach as closely as possible) while also electrically & magnetically inert. The best overall material that's commonly available is lead. It's very dense, it doesn't tend to accumulate static electric charge, and is magnetically unresponsive.

[lhkjmvnb]

Actually, you would expect a much stronger force. G is to the power of -11.

[AndrewwwRoan]

mmm , no muy mal , quien alla echo este video muy mal

para imajenes crei que mejor busco en una pagina diferente

[gibbo1112]

@johnbunsenburner it is a very good conductor, not good

[Mrjellykid]

tomorrow is my physics paper

[SheerPandemonium]

@PerfectBlindness use nonmagnetic materials....

[qed100]

@johnbunsenburner

Yes, I see your point. It's even more dense than Uranium.

[johnbunsenburner]

@qed100 I would say that gold would be the "best overall material" considering its density and how inert it is ect. However there are other limitations that make it a less attractive choice compared to lead. Also one must consider the composition of the rest of the apparatus, not just the weight to allow for a truely fair test.

[PerfectBlindness]

Thankyou, It's interesting because if you swapped the weights on the ends of the torsion balance for strong magnets of equal weight, you'd expect the same result.

[PerfectBlindness]

how do you know it's not some other effect? like magnetisim?