Empirical Earth · Gravity, Buoyancy & the Air

How gravity works — and why “you can’t explain it” isn’t a gotcha

The claim

“Nobody can explain what gravity is or how it works at the atomic level, so it’s a fudge — really it’s just density and buoyancy.”

What is measured

Gravity is described by Newton’s force law and Einstein’s curved spacetime. It passes every test and is measured directly between masses down to about 90 mg. It is the weakest force (about 10³⁶× below electromagnetism), so it is tiny between atoms but dominant for worlds. Lacking a quantum theory of gravity is a frontier, not a fudge, and buoyancy is a result of gravity, not a replacement for it. Where gravity sits among the others is covered in the four fundamental forces.

What would show this is wrong

a demonstration that objects in a vacuum fall at rates set by their density instead of all the same; a repeatable measurement showing no gravitational attraction between isolated laboratory masses (contradicting Cavendish and the 2021 milligram result); or a working “density-and-buoyancy” account that needs no downward pull to make a fluid push lighter things up.

Sources

  1. Smallest gravity ever measured — ~90-mg gold spheres. Westphal et al. (Vienna, 2021) measured the gravitational pull between two gold spheres of ~90 mg with a torsion balance; the result mat link
  2. Gravity vs. the electric force — how they differ. Both obey an inverse-square law, but gravity is always attractive (mass has one sign) while the electric force attracts or repels; between a link
  3. Faraday’s search for a link between gravity and electricity (1849–1850). His diary for 19 March 1849 records the conviction that gravity must have “an experimental relation to Electricity, M link
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