Earth, physics and evolution

Recently I’d seen a physicist’s opinion that the earth should be much warmer than it is, given it’s proximity to the sun. Implicit was the theory that the chemical make-up of the earth allowed life to develop here – and that life itself was storing energy.

Does anyone know what this theory is called?
Where there’s more information on it?


That sounds kind of like the Gaia hypothesis proposed by James Lovelock.

He proposed DaisyWorld. A world like earth, but the only living things on the planet are daisies and they come in two varieties, white and black. The white ones reflect back the sun’s radiation and the black ones absorb the radiation causing heat. If the planet is a little too cool, black daisies will be favored until the temperature is optimum for daisies. If the planet is a little to warm, white daisies will flourish until enough radiation is reflected back to cool the planet to the optimum for daisies. So, on DaisyWorld, life regulates the temperature to suite itself.

Yeah, I think the OP is talking about the Gaia hypothesis.

Supporters of the Gaia hypothesis often mention the Faint Young Sun Paradox: the Sun’s intensity has increased by about 30% over the past 4 billion years, yet Earth evidently wasn’t a frozen ball of ice during the crucial early period when life was evolving. It’s been suggested that the chemical changes to Earth’s atmosphere wrought by evolving life “balanced out” the gradually increasing solar radiation. (I believe it may have been the Faint Young Sun Paradox which inspired the Gaia hypothesis in the first place.) The connection between the two is discussed here, as well as a more detailed discussion of the FYSP.

However, evidence has been accumulating that Earth has, at times in the past, been a “frozen ball of ice,” yet life survived. See this Scientific American article: Snowball Earth.

Actually, given its proximity to the sun, the Earth should be much colder than it is. Fortunately for us, the atmosphere provides a mild greenhouse effect to keep us cozy & warm. (The “global warming” concern now is over the possibility of increasing the greenhouse effect to uncomfortable/dangerous/damaging levels.)