1122 
thick and heavy ionization tracks which, compared 
with effects of alpha rays, should be strong enough to 
endanger lives exposed for more than one hour [53, 77]. 
2. The cabin climate of a craft at an altitude of more 
than 150 km, coasting along a celestial orbit after 
power shutoff, would be characterized by radiation 
equilibrium of the hull and lack of air convection in- 
side. The surface temperature depends on the following 
radiations in addition to interior heating: sun, solar 
radiation reflected from the earth, and the radiation 
from the earth and cosmos. The main material con- 
stant is the ratio of the absorption coefficient at A < 
3. to that of \ > 3u. This ratio equals 1.0, 0.1, and 6.0 
for ideal black, white, and metallic surfaces, respec- 
tively. With a solar constant of 1200 Calm” hr’, an 
average earth albedo of 0.42, and an average earth 
radiation of 174 Calm” hr *, equilibrium temperatures 
are found [23] for a sphere, a plate always facing the 
sun, and a plate always facing the opposite direction 
(Table IV). The temperatures are higher than one 
might expect. 
TasLe IV. EquiniBRiuM TEMPERATURE OF A SOLID SURFACE 
OUTSIDE THE ATMOSPHERE BUT CLOSE TO THE HARTH 
Day Night 
Form of surface 
black white | nickel all 
XG 5G CG °¢ 
SpDHETE a. Sars cee eee eee +63 | —42 | +239 —68 
Plate facing the sun........... +122 | —51 | +347 —29 
Plate facing the opposite direc- 
11310) eee none meal Sa re +68 | —13 | +231 | —270 
If the earth’s gravity is balanced by the centrifugal 
forces of the flight trajectory, gravity within the craft 
is absent and convection consequently ceases (see equa- 
tion (3)). Exchange of heat, water vapor, respiratory 
gases, settling of dust, etc., can take place only by 
processes such as artificial ventilation and filtering. 
The thermal insulation of thick air layers would be 
equivalent to that of stagnant air of this thickness. 
3. Lack of gravity may influence the human sensory 
system in a way and to an extent which cannot be 
predicted. 
Effects of Extreme Heat and Cold [22, 45, 62, 73]. 
All the formulas on heat exchange of the human body, 
described in the first section, are based upon the as- 
sumption of a steady state. The skin and rectal tem- 
perature changes are too small to cause additional 
factors in our equations, except the simple one con- 
cerning any slow, temporal, linear increase of the body 
temperature as a whole. 
If, however, heat transfer to the skin surpasses 500 
to 1000 Cal m ~* hr“, the simplification of a steady state 
no longer holds, and the differential equation of heat 
conductivity has to be applied in full. 
When heat or cold is applied during a short period of 
time, generally less than one minute, the skin tempera- 
ture changes according to the amount and kind of heat 
transfer (Newtonian, constant nonpenetrating heat, 
constant penetrating radiant heat, contact heat, etc.) 
and according to the material and initial temperature 
BIOLOGICAL AND CHEMICAL METEOROLOGY 
of the skin. The temperature change of the surface 
proper generally depends on only one constant, the 
product of three characteristics (heat conductivity xX 
density X specific heat) of the skin at the surface. This 
product was shown experimentally to lie between the 
values of water and fat, and not to depend on the blood 
flow. With this experimental fact sudden temperature 
changes of the skin can be calculated (formulas in [22, 
25, 45, 62, 73]), for example, for the rapid cooling in 
very cold wind, according to measurements of Siple 
[79] and Buettner [22], or heating by solar radiation [73]. 
PROBLEMS FOR FUTURE RESEARCH 
Bioclimatology is essentially an applied science. As 
such, it can be expected to experience changes in its 
major problems as a consequence of progress made in 
related fields. Taking tropical medicine as an illustra- 
tive example, we may note that it may one day find 
itself in the position of being confined to problems of 
sultriness and sunstroke as soon aS progress in epi- 
demiology will have eliminated the major objectives 
currently being pursued. From this point of view, heat 
and cold merit serious considerations as basic and 
isolated problems. Few thermal measurements have 
been made on clothed people exposed to the actual 
environment of various climates, whereas ample data 
exist for nude subjects under the artificial conditions 
of a climatic chamber. These conditions fail to account 
for the variation of some important factors, chief among 
them being rapid changes in the wind speed. These 
variations may cause variations in the skin tempera- 
ture, but to a varying degree, depending on the situa- 
tion, because cooling power depends on +/v, air trans- 
port on v, and wind pressure on v. Temperature and 
radiation are also subject to rapid meteorological 
changes. 
It is believed that there exists a pronounced dis- 
proportion between competitive formulas and instru- 
ments designed to determine the “dry” cooling and 
their application in the practice of physicotherapy, 
comparative climatology, clothing design, and building 
construction. In fact, the excellent work carried out on 
clothing by the Office of The Quartermaster General, 
U. S. Army, had to be accomplished mainly without 
the use of ‘‘cooling power.” There is much left to be 
done in the study of the effects of strong winds on 
clothed bodies. More open-air studies can be expected 
to yield stress data, integrating the effects of heat and 
humidity. 
Even if all these formulas were on hand, their cli- 
matological use would be impaired by the lack of data 
on wind velocity near the ground, radiation, vapor 
pressure, and soil temperature. Typical climatological 
data are more useful to a botanist than to a physician. 
On a climatological map the summer climate of, say, 
El Paso and San Antonio, Texas, look nearly alike. 
But the difference in vapor pressure makes the two 
localities very different in their habitability. 
As far as solar ultraviolet radiation is concerned, it 
is still uncertain whether it is beneficial in all cases or 
not. Its absence has sometimes been observed to coin- 
