The Sun 



The following account of the sun is a part of an address by Professor W. W. 

 Campbell of the Lick Observatory delivered at the dedication of the Warner 

 and Swasey Obersvatory in Cleveland, Oct. 12, 1920 and printed in Science, 

 Dec. 10, 1920. 



The wonders of our sun are many and most remarkable, and Are 

 but little known. I have referred to its enormous size. The 

 quantity of heat which the sun is radiating into surrounding space, 

 to the earth, to Mars, and to all other objects which intercept its 

 rays, is stupendous and not to be comprehended by the astronomer 

 or the man of affairs. It is, and has been, the source of all the 

 energy upon which we draw, save only a negligible residual. A 

 great quantity of heat is indeed stored up in the interior of the 

 earth, but it reaches the earth's surface in such minute quantities 

 that in all practical details of life, save to those who labor in deep 

 mines, or live near volcanoes, or are interested in hot springs, this 

 source of energy may be neglected. If this statement should be 

 difficult to accept, let your thoughts travel to the south pole of our 

 planet. What does the interior heat of the earth do for that re- 

 gion? The antarctic continent's perpetual covering of ice and 

 snow is unaffected by it, nor does the actually enormous quantity 

 of solar heat falling upon that continent suffice to remove the white 

 mantle. If aught should intervene to cut off the sun's energy 

 from the earth for one short month, the tropics would attain to a 

 state of frigidity to which the south polar continent, as now 

 observed, would be a rose garden in comparison. 



It is the sun's heat which grows the farmers' crops, the trees of 

 the forest and all vegetation. The coal df^posits upon which we 

 draw toda}^ for the running of trains, ships, factories and rolling 

 mills, are but the solar energy of an earlier age, compressed, trans- 

 formed and preserved for our comfort and power. In the moim- 

 tainous regions of our land, where water can be stored in high level 

 reservoirs and, passing through water wheels at lower levels, be 

 made to generate electric power for lighting, for heating and for the 

 running of motors, it is the sun's energy which is transformed 

 to meet the needs of men. The sun's rays evaporate the surface 

 waters of the oceans, lakes, streams and lands; the winds, genera- 

 ted by the unequal solar heating of our atmosphere, transport 

 some of the water vapor to the high mountains, where it is deposited 

 as rain or snow. It is merely the descent of these waters to the 



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