The simple _reflected_ heat must follow the same law
as moonlight, and come to its maximum at full moon. The _radiated_
heat, on the other hand, will reach its maximum when the average
temperature of that part of the moon's surface turned toward the earth
is highest; and this must be some time after full moon, for the same
sort of reasons that make the hottest part of a summer's day come two
or three hours after noon.
The conclusion early reached by Lord Rosse was that nearly all the
lunar heat belonged to the second category--dark heat _radiated_ from
the moon's warmed surface, the _reflected_ portion being comparatively
small--and he estimated that the temperature of the hottest parts of
the moon's surface must run as high as 500 deg. F.; well up toward the
boiling-point of mercury. Since the lunar day is a whole month long,
and there are never any clouds in the lunar sky, it is easy to imagine
that along toward two or three o'clock in the lunar afternoon (if I
may use the expression), the weather gets pretty hot; for when the sun
stands in the lunar sky as it does at Boston at two P.
Pages:
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144