Empirical Earth · Gravity, Buoyancy & the Air
Gas under gravity — pressure, the gas laws & your own lungs
The claim
“If gravity pulled on air, the heavy gases would all sink and we’d suffocate — gas can’t be held by an invisible force.”
What is measured
Gases obey PV = nRT to high precision in any lab; the same physics holds the atmosphere down with no dome or wall required. The barometric equation and where g enters the gas laws are in the gas laws and gravity.
What would show this is wrong
gases departing from PV = nRT under controlled temperature and pressure.
Sources
- Atmospheric structure, scale height & escape. Pressure falls exponentially, H = kT/(mg) ≈ 8.5 km; no hard boundary (Kármán line is a 100 km convention); thermal/Jeans escape slowly leaks lig link
- Ideal gas law & kinetic theory. PV = nRT relates pressure, volume, temperature and amount of gas; gases have mass (sea-level air ~1.2 kg/m³) and exert pressure (~101 kPa at sea level) becaus link
- Pulmonary ventilation/perfusion gradient (West zones). Standing, both blood flow and air reach the base of the lung more than the apex because of gravity, so oxygenation depends on posture — link
- Pascal’s Puy de Dôme barometer experiment (1648). Florin Périer carried a Torricelli barometer up the Puy de Dôme for Blaise Pascal: the mercury fell from 711 mm at the base to ~627 mm about link
- Gas centrifuge — isotope separation by an effective gravity field. A spinning rotor creates a field of order 10⁵–10⁶× gravity; heavier UF6 molecules (U-238) move to the wall and lighter ones link
The full entry, with the working →