XI

THE LIGHT OF THE FUTURE

In viewing the development of artificial light and its manifold effects upon the activities of mankind, it is natural to look into the future.  Jules Verne possessed the advantage of being able to write into fiction what his riotous imagination dictated, and so much of what he pictured has come true that his success tempts one to do likewise in prophesying the future of lighting.  Surely a forecast based alone upon the past achievements and the present indications will fall short of the actual realizations of the future!  If the imagination is permitted to view the future without restrictions, many apparently far-fetched schemes may be devised.  It may be possible to turn to nature’s supply of daylight and to place some of it in storage for night use.  One millionth part of daylight released as desired at night would illuminate sufficiently all of man’s nocturnal activities.  The fictionist need not heed the scientist’s inquiry as to how this daylight would be bottled.  Instead of giving time to such inquiries he would pass on to another scheme, whereby earth would be belted with optical devices so that day could never leave.  When the sun was shining in China its light would be gathered on a large scale and sent eastward and westward in these great optical “pipe-lines” to the regions of darkness, thus banishing night forever.  The writer of fiction need not bother with a consideration of the economic situation which would demand such efforts.  This line of conjecture is interesting, for it may suggest possibilities toward which the present trend of artificial lighting does not point; however, the author is constrained to treat the future of light-production on a somewhat more conservative basis.

At the present time the light-source of chief interest in electric lighting is the incandescent filament lamp; but its luminous efficiency is limited, as has been shown in a previous chapter.  When light is emitted by virtue of its temperature much invisible radiant energy accompanies the visible energy.  The highest luminous efficiency attainable by pure temperature radiation will be reached when the temperature of a normal radiator reaches the vicinity of 10,000 deg.F. to 11,000 deg.F.  The melting-points of metals are much lower than this.  The tungsten filament in the most efficient lamps employing it is operating near its melting-point at the present time.  Carbon is a most attractive element in respect to melting-point, for it melts at a temperature between 6000 deg.F. and 7000 deg.F.  Even this is far below the most efficient temperature for the production of light by means of pure temperature radiation.  There are possibilities of higher efficiency being obtained by operating arcs or filaments under pressure; however, it appears that highly efficient light of the future will result from a radical departure.