(urth) Green Is Urth Redux

[Lee Berman]

> Hypothesis 1: Lune is Moon-sized and we can assume there is an unmentioned power source.
>
> Hypothesis 2: Lune is Urth-sized and we can assume its forests are maintained by the same power source as
> Urth's forests- the sun.
 
 
>Jeff Wilson- Why would the sun shine less brightly on a smaller body than on a larger 
>one?
 
I don't understand this question. The Sun shines about as brightly on the Moon as on Earth. The main reason
our Moon doesn't have plants is that it doesn't have an atmosphere. An atmosphere is necessary to provide
CO2 and 02 of course. But it also provides the possibility of surface water. With 0 atmospheric pressure, 
all water would boil off into space. There is temperature buffering and regulation also.
 
If Lune is as small as Moon, it needs a technology-based power source to allow plant growth. That's all. If
Lune is as big as a planet and has an atmosphere, it can have plant growth even if there is no technology
present to sustain it.
 
 
>David Stockhoff- Incidentally, does anyone see any problems with the Moon getting either not enough or too much 
>sun for photosynthesis? 
 
Surely. If the simple stripping of earth's thin ozone layer might play havoc with plant growth, the absence of an 
entire atmosphere would make things much more difficult. Plants are not green by accident. That color provides
maximum efficiency of energy utilization for the light that reaches earth through an atmosphere. The fact that
Lune's plants are green suggests either that Lune has an earth-like atmosphere or that it has mechanisms to 
artificially ensure that the light which hits the plants on Lune is roughly identical to the light that hits 
Urth (or earth). 
 
(we are told that the greenness of Urth plants is not the same greenness as for Earth plants; in truth a red sun
probably would not produce enough of the proper energy on Urth to allow the diet that Severian eats. He probably
would be restricted to eating fungi, deep-water algae, maybe lichens or other low-intensity light utilizing
plants. Casual meat-eating would be an insane luxury under such conditions).