Dne 04/12/2016 v 12:18 Mike Dworetsky napsal(a):
Poutnik wrote:

Hm, this is refuted by huan eyes look.
Earth in visible region is far from black body behavior.

True. I said "reasonable approximation". Human eyes are unable to
detect IR radiation.

But that has nothing to do with if wtwasfetect it or not.
For visible range, BB is not reasonable approximation.


The very most surfaces are far from be anywhere near the black.

Surfaces are close to BB in terms of absorption and radiation. But the
atmosphere is not.

Surfaces are close to BB in terms of absorption and radiation
for thermal IR.
Athmosphere is close to BB in its IR absoption window.


.......... But the atmosphere tends to
block and reflect some of that IR radiation.

And emit like BB with T lower than surface.


Contrast Venus, which has a very thick and opaque atmosphere. The IR
radiation comes from the upper atmosphere, but the surface is much
hotter. When Venus is studied at radio wavelengths, it looks hotter
because the waves penetrate the clouds and we observe the hot surface
directly.

As above, for absorbing WL the atmosphere acts like BB.

--
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.