Why is the Earths core warm

[url] www.thesurfaceofthesun.com/model.htm ?[/url] More thinking like Don Scott's regarding the sun.

That surface greyness of the Earth I wrote about 3 June, is readily apparent in infrared videos, where humans appear white through light and dark grey, depending on how they dress. Only their retinas, glowing through pupils, the only clear windows showing core body temperatures, are like black-body radiators. Most other infrared radiations are absorbed or reflected inwards (keeping them warm), more than are emitted by their skin, hair and clothing.

The Earth and other planets are similarly enveloped, at larger scales, by surface components of low emissivity, layers of gases, liquids, solids which absorb infrared radiations, reflect them inwards and so on in much the same way as human clothing.

You got the right idea about insulation warming a blackbody holding heat in and keeping energy from radiating away. But, any blackbody at any temperature radiates the same as any other blackbody whatever kind of stuff either body is made of. A numan body or a planet is insulated and kept warm but it still radiates blackbody energy. Thats why the mantle of Earth is 2,000 degrees and the surface is 25C or so on average. The crust insulates the mantle and keeps it warm.

Yes Jim, You can look at it that way, blackbodies insulated by grey layers, but the overall, greybody effect is the same, the Earth and most other planets are effectively grey bodies, unlike stars and other plasmas, the major part of the Universe.

I do not know how black even plasmas are . . .

All atoms tend to have characteristic absorption-emission spectra at all temperatures, and real masses are mostly layered as stars, planets and so on, so one should expect that "insulation-envelope effect" we dialogued about for planets, to apply to stars as well, possibly even to superhot plasmas beyond atomic states, because even these have quantum states, which is what gives rise to absorption-emission spectra . . .

Peter, I agree with you about insolation but not the graybody model. Graybody modeling is a kind of fudging and a way to hide facts as is done with the energy balance of Earth. They call Earth a graybody and so the fact the surface is radiating about 500w/m^2 doesn't count which seems to me to be a way to not think about it. You just accept the graybody modeling and never mind that fact.