The Arizona sentinel., 1896-08-08
How Long can the Earth Sustain Life!

How Long can the Earth Sustain Life!
 There is a boundary to the prospect of the continuance of the suns radia- tion. Of course, as the loss of heat goes on, the gaseous parts will turn Einto liquids, and as the process IS still
 further protracted, the liquids will
 transform into solids. Thus we look forward to a time when the radiation
 of the sun can be no longer conducted
 in conforming with the laws which
 dictate the loss of heat from a gaseous
 body. When this state is reached the
 sun may, no doubt, be an incandes-
 cent solid with brilliance as great
 as is compatible with that condition,
 but the further loss of heat will then
 involve loss of temperature. At the
 present time the body may be so far
 gaseous that the temperature of the
 sun remains absolutely constant. It
 may even be the case that the tenn
 perature of the sun, notwithstanding
 the undoubted loss of heat, is abso-
 lutely raising.
 It is, however, incontrovertible that certain maximum temperature hay ing been reached (whether we have reached it not we do not know), tenn perature will then necessarily decline. There is certainly no doubt whatever that the sun, which is now losing heat, even if not actually failing in temperature, must, at some time, be- gin to lose it's temperature. Then, of course its capacity for radiating heat will begin to abate. The heat received by the earth from the great center of our system must, of course, decline. There seems no escape from the con- clusion that the continuous loss of solar heat must still go on, so that the sun will pass through the various stages of brilliant incandescence, of glowing redness, of dull redness, until it ultimately becomes a dark and non luminous star. In this final state the | sun literally joins the majority. Every analogy would teach us that the dark | and non-luminous bodies in the uni verse are far more numerous than the brilliant suns. We can never see the dark objects, we can discern their presence only indirectly. All the stars that we can see are merely those bodies which at this epoch of their career happen for the time to be SO highly heated as to be luminous.
 There is thus a distinct limit to mans existence on the earth, dic- tated by the ultimate exhaustion of the sun. It is, of course, a question of much interest for us to speculate on the probable duration of the suns beams in sufficient abundance for the continued maintenance of life. Per haps the most reliable determinations are those which have been made by Professor Langley. They are based on his own experiments upon the intensity of the solar radiation, con- ducted under circumstances that give them special value. l shall endeavor to give summary of the interesting results at which he has arrived. The utmost amount of heat that it would ever have been possible for the sun to have contained would supply its for 1S,000,000 years at the present rate. Of course, this does not assert that the sun, as radiant body, may not be much older than the period named. We have already seen that the rate at which sunbeams are poured forth has gradually increased as the sun rose in temperature. In the early times the quantity of sum- beams dispensed was much less per annum than at present, and it is, therefore, quite possible that the figures may be so enlarged as to meet the requirements of any reasonable geological demand with regard to past duration of life on the earth.
 It seems that the sun has already | dissipated about four-ffths of the energy which it may have originally been endowed. At all events, it seems that, radiating energy as its present rate the sun may hold out for 4,0G0- 900 years, of for 5,000.000.