Sun, Sea, and Air’ 
By Rocer REVELLE 
Director, Scripps Institution of Oceanography 
University of California 
La Jolla, Calif. 
Tue Great saca of the Norse kings, the “Heimskringla,” begins 
with the words “Earth’s round face, whereon mankind dwells.” The 
Vikings, like other primitive peoples, thought of Earth as their home 
and of themselves as its creatures. Today we know that Earth is the 
only planet of our solar system on which human life could have 
developed, for no other satellite of our sun has land masses sur- 
rounded by an ocean of liquid water or an atmosphere containing 
abundant free oxygen. 
Our bodies are made up almost entirely of four elements drawn 
from sea water and air: hydrogen, carbon, oxygen, and nitrogen. 
The narrow temperature range in which we can survive is maintained 
by the great heat capacity of the sea and the atmosphere. The waste 
products that otherwise would suffocate us are continuously dispersed 
by the easy motions of the atmosphere. We can exist as land animals 
only because the sun’s deadly ultraviolet and X-rays are fended off 
by the protective shield of the air, and because the great natural en- 
gine of the sea and the atmosphere pumps water continuously from 
the sea surface and pours it gently down upon the land. 
Yet from our point of view, the earth is a careless mother. Large 
areas of her surface are too hot or too cold, too dry, or too wet to sup- 
port any large number of human beings. Moreover, she is unreliable. 
Areas where there was once sufficient water for men to build civiliza- 
tions are now so dry that only a few desperate nomads can live in them. 
Elsewhere, a mile-thick blanket of ice has crept down and obliterated 
once green farms and forests. Millions of our species suffer when a 
slight change in the running of the sea-atmosphere engine causes 
drought or flood. Sometimes the engine runs with unpleasant violence. 
Then thunderstorms and hurricanes, tornadoes, and typhoons bring 
destruction and death to many of us. 
1 Reprinted by permission from Oceanus, vol. 5, Nos. 3 and 4, summer and autumn 1957. 
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