Empirical Earth · Gravity, Buoyancy & the Air

Cavendish weighed the Earth with two lead balls

The claim

“Gravity between ordinary objects has never been measured — it’s really just density and buoyancy.”

What is measured

Two lead balls in a sealed room visibly attract each other. The force is gravitational, grows with mass, and gives Earth’s density (~5.5× water). That single experiment, repeated in labs every year, refutes “gravity is just density” and weighs the planet.

What would show this is wrong

a torsion-balance measurement showing no attraction between the masses, or a buoyancy-only mechanism that reproduces the sideways pull between two lead spheres in a sealed, fluid-free setup.

Sources

  1. The Cavendish experiment (1798). Henry Cavendish used a torsion balance to measure the gravitational attraction between lead spheres, deriving Earth’s mean density as ~5.45–5.5 times that of link
  2. Cavendish torsion-balance apparatus. Lead balls of 0.73 kg on a suspended rod were drawn aside by 158-kg lead spheres; the restoring twist of the wire gave the gravitational force between th link
  3. Michell and the Cavendish experiment. The experiment was devised before 1783 by the geologist John Michell, who built the torsion balance but died in 1793 without completing it. The apparatu link
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