Empirical Earth · Gravity, Buoyancy & the Air

The second law of thermodynamics — Earth is an open system

The claim

“Entropy always rises in a closed system, so a far-off Sun heating us through cold space breaks the second law.”

What is measured

Earth is an open system: it absorbs about 240 watts per square meter (W/m²) of sunlight and radiates nearly the same back to space as infrared. The second law governs the whole Sun–Earth–space system, where entropy rises, not a sealed box under a dome.

What would show this is wrong

a calibrated infrared radiometer aimed at the night sky reading at or above the local air temperature, meaning no net heat leaving Earth for space. In reality it reads far colder, because you are watching the planet radiate.

Sources

  1. Earth’s energy budget. NASA describes Earth’s climate as a solar-powered system that absorbs on average about 240 watts of sunlight per square meter and radiates the same amount back to spac link
  2. Isolated, closed and open systems. In thermodynamics an isolated system exchanges neither matter nor energy with its surroundings, a closed system exchanges energy but not matter, and an ope link
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