TEMPERATURE OF SPACE. 259 



sun, but unless we know the temperature of space 

 we cannot say how much this one-fourth raises the 

 temperature of the Atlantic. Suppose 56° to be the 

 temperature of that ocean ; this is 517° of absolute 

 temperature which is derived from three sources, viz. : 

 (1) direct heat from the sun, (2) heat from the Gulf 

 Stream, and (3) heat from the stars. Now, unless we 

 know what proportion the heat of the stars bears to 

 that of the sun, we have no means of knowing how 

 much of the 517° is due to the stars, and how much to 

 the sun or to the Gulf Stream. 



M. Pouillet, Sir John Herschel, and Professor 

 Langley are the only physicists who appear to have 

 devoted attention to the problem. M. Pouillet came 

 to the conclusion that space has a temperature of 

 - 142° C. or - 224° F, and Sir John Herschel, following 

 a different method of inquiry, arrived at nearly the 

 same result, viz., that its temperature is about - 239° F. 



Can space, however, really have so high a tempera- 

 ture as - 239° ? Absolute zero is - 461°. Space in 

 this case would have an absolute temperature of 222°, 

 and consequently our globe would be nearly as much 

 indebted to the stars as to the sun for its heat. If so, 

 space must be enormously more transparent to heat 

 rays than to light rays. If the heat of the stars be 

 as feeble as their light, space cannot be much above 

 absolute zero, and this is the opinion expressed to me 

 a short time ago by one of the most eminent physicists 

 of the day. Professor Langley is also of this opinion ; 

 for he concludes that the amount of heat received 

 from the sun is to that derived from space as much 

 as four to one ; and consequently if our luminary 

 were extinguished, the temperature of our earth 

 would fall to about - 360° F. 



It must be borne in mind that Pouillet's Memoir 



