53(5 
rPvOFESSOR J. IT. POYXTTXG ON PADTATIOX IX THE SOLAP S55^TE.\1 
Variation of Temperatnre u'lth, Distance from the Sun. 
Since the radiation received varies inversely as the square of the distance from the 
sun, that given out varies in the same ratio. The temperature of the radiating 
surface varies therefore as the fjurth root of the inverse square, that is inversely as 
the square root of tlie distance. 
il'his enables us to deduce at once the temperatures of the various surfaces and 
bodies which we have considered, if placed at the distances of diflerent planets as well 
as at tlie distance of tlie earth. We have merely to multiply the results liitherto 
found 1)V 
V 
Earth’s distance 
Planet’s distance 
The following talile contains the values of the temperatures at selected distances, 
all on the absolute scale :— 
TaiUiL: of Temperatures of Surfaces at Different Distances from the Sun, All on 
the Ah'solute Scale. 
At the 1 
distance of 
the planet. 
Eistance. 
Eartli’s 
distance = 1. 
' Square root ' 
of 
' (distance)“^. 
Equatorial 
tempera¬ 
ture 
of ideal 
planet. 
Average 
tempera¬ 
ture 
of ideal 
planet. 
Upper limit 
of a surface 
reflecting 
one-eighth 
under 
zenith sun. 
Average 
tempera¬ 
ture of 
equivalent 
disc. 
Tempera- ^ 
ture 
four-fifths 
that of 
equwalent 
disc. 
Tempei’a- 
ture of 
small 
absorbing 
sphere. 
! b 
II. 
III. 
lY. 
V. 
YI. 
YII. 
YIII. 
IX. 
Mercuiy . 
0-3871 
1-61 
502 
467 
664 
598 
478 
483 
Venus 
0-7233 
1-18 
368 
342 
486 
438 
350 
358 
Earth . . 
1-0000 
1-00 
312 
290 
412 
371 
297 
300 
1 
Mars . . 
1-52.37 
0-81 
253 
235 
337 
300 
240 
243 
Xeptune . 
! 30-0544 
0-18 
56 
1 
52 
74 
1 
67 
53 
54 
We have omitted the larger planets except Neptune, since in all probability the} 
radiate lieat of their own in considerable proportion. Neptune is inserted merely to show 
how low temperatures would be at his distance if there were no supply of internal heat. 
The results given in the table may not be exactly applicable to any of the planets, 
Imt they at least indicate the order of temperature which probably prevails. 
If, for instance. Mars is to be regarded as having an atmosphere with regulaiing 
pi'operties like our own, his equatorial temperature. Column lA ., is pi'obalily far belov 
the temperature of freezing water, and his average temperature, Column A., must be 
not very diffbrent from tliat of freezing mercury. It, on the other hand, we suppose 
that Ids atmos})liere has no regulating power, we get the upper limits not very 
