Why is the Earths core warm

Peter, The thing is air is all that exists between the surface of Earth and space. Are you saying air is that good at insulating? And if it is that good at insulating infrared from the surface why does sunlight get to the surface? I know it is said carbon dioxide does allow this to happen but does air? Remember, the Earth is 2,000 degrees a few miles beneath the surface so some energy must flow from there to the surface. What about that energy? And, I know they say it is not very much.

Yes Jim, It's all about insulation, very effective insulation against radiative, conductive, convective transfer of heat by the many insulating layers of crust and atmosphere at the surface of the Earth.

H2O is the most powerful radiative insulator in the atmosphere, while even dry air strongly absorbs solar radiation, ~50%?!?!?. There was a spectrum showing this in one of those Googled items I referred to earlier.

Low level cloud most strongly reflects incoming Solar radiation, so has a cooling effect. High level cirrus cloud, being ice, lets most of this in, while strongly reflecting outgoing infrared radiation, so has a warming effect. Hence worries about jet aircraft contrails.

So you say the Earth is as warm as it is because the atmosphere absorbs energy and does not radiate as a blackbody does? That seems to be a conflicting conclusion. Of course it does not matter to a model but the real effects would be different. The Earth is warm and radiates as a blackbody. I don't think anyone would be able to prove the Earth does not radiate very nearly as an ideal blackbody would. Some would say the Earth radiates as a blackbody at ~255 kelvin because the atmosphere insulates the surface from space and this is what I have a problem with. Assuming the blackbody temperature of 255 kelvin and knowing the surface is ~290 kelvin assumes the air is a oneway insulator in that solar energy can get in but can't get out. There is a mindless belief that defys the law of blackbodies. Would you therefore say that law is wrong?

The real Earth is an imperfect black body. The white patches (clouds) would be radiating at ~255K, while the dark patches (ocean) would be radiating at ~300 near the equator, ~273K near the poles. These would be imperfect blackbody radiations because even dry atmosphere has strong bands of absorption, while the water itself would also have spectral as well as blackbody emissions. Likewise the green and brown land patches.

There are some areas of the planet that radiate at temperatures that differ from the average blackbody temperature simply because the average blackbody is a composite of all the areas of Earth so you are correct in pointing that out. The point that to be determined is the average blackbody temperature of the planet. The surface has an average temperature of somewhere between 290 and 300 kelvin. It seems Earth has a warm/cold cycle that ranges within 10 degrees. So, that means on average the Earth radiates ~450 watts per square meter or more. It is more simple to use the radiation power rather than the temperature. That way you can see how much energy needs to be accounted for and the source identified. The solar constant is 1370 watts per square meter for the Earth/moon system and the surface of Earth gets about 250w/m^2 on average. Of that about 75w/m^2 is used to power the weather. So, maybe 175w/m^2 actually warms the surface and since the surface is radiating 450w/m^2 there is 275w/m^2 that is undocumented energy. This seems to me to be an oversight that should be fixed and factored into models.

The earth's core is hot because it is not billions of years old as you assume. I suspect God made it that way to see how many ridiculous theories people could come up with to attempt to explain why. [8D]

Romans 1:25 "They exchanged the truth of God for a lie..."