On Fri, 26 Jun 2015 23:19:34 +0100, Charlie Pridham wrote:


"Tough Guy no. 1265" wrote in message
news
If a person wears clothes, their bodyheat is trapped, and they become
warmer. But a plant does not generate heat, so how can covering it in a
blanket stop it getting frozen in winter?

Everything at a higher temperature will lose heat to something at a lower
temperature, since outer space is always a lot colder than planet earth
everything radiates heat upward the whole time (actually in all directions
but up is the important one for gardeners), at some times the heat lost is
balanced by warm air (as in summer) sometimes the heat being radiated up
bounces back because its hit water molecules in the atmosphere (or the
leaves of a tree) the fleece mimics this. Fleece will only conserve heat, so
once its gone plants will still get damaged, often however its enough.
It makes a lot of difference what the surface area is compared with the
mass, grass blades have a large surface area and little mass so their
temperature can easily dip below that of the surrounding air giving a grass
frost even when the air temperature is +3 or 4c.

I see, thanks.

--
Please do not look into laser with remaining eye.