wrote in message
...
On Thu, 15 Jul 2004 05:52:23 +0000 (UTC), "Franz Heymann"
wrote:

That is not true. It absorbs infrared radiation.

I thought you might says that :-)

and you didn't mention black body radiation.

Firstly, the glass is not a black body. {:-))

{:-)) ---------the trademark of the real Franz.

Yes. In addition I also don't talk as much rubbish as the impostor
using my name. {:-))
The "{" is a matter of wishful thinking, since I have practically no
hair left.

That's probably why you didn't mention it then :-)

Secondly, reradiation is not reflection.

yes

Thirdly, reradiation is not the only (or even the major?) process
by
which the heat is retained in the gteenhouse. Convection is very
important.

and insulation?

You have a point. The major reason why a greenhouse retains heat is
actually that it prevents the hotter interior from cooling by large
scale convection. All this stuff about the glass absorbing the
infrared radiation emitted by the contents of the greenhouse is small
beer compared with the simple mechanical shielding offered by the
structure. This is illustrated nicely by the fact that a greenhouse
cools off when all the ventilators are opened wide.

[snip]

Franz