00100	To the Editor:
00200	
00300		David C.  White's projections of energy demand are  extremely
00400	unconvincing  without  some information about what all this energy is
00500	to be used for.      After all,  a  judicious  choice  of  years  for
00600	estimating U.S. consumption of meat would lead to the conclusion that
00700	we shall each eat a cow a day by the year 2100 and ten cows a day  in
00800	another few hundred years.
00900	
01000		Simple-minded projections of percentage increase rates in use
01100	of a commodity are bound to be misleading if  carried  too  far.    A
01200	realistic   estimate  of  U.S.    energy  requirements  must  include
01300	considerations like the following:
01400	
01500		1.    Will our space heating requirements per capita increase
01600	through   bigger  houses,  worse  insulation,  or  more  non-dwelling
01700	buildings?
01800	
01900		2. When will our increasing levels of lighting saturate?  How
02000	much lighting to the well-to-do use as compared to the poor?
02100	
02200		3.  How much will energy use in transportation increase?   If
02300	transportation is to do its share in meeting your energy  consumption
02400	increases, we shall have to have three cars apiece and drive them all
02500	the time.
02600	
02700		4.  How is the use of energy in industry changing?   What use
02800	of  energy  is  required  for  the  changes in technology that may be
02900	projected over the next 50 years?  Projections over 100 years are  as
03000	idle  as  projections  of today's technology made 100 years ago would
03100	be.
03200	
03300		5.   Since  your  projections  of  energy  use  do  not  show
03400	reductions  in  cost,  when  would  the  cost  of  energy  consume an
03500	implausibly large fraction of people's incomes?
03600	
03700		I cannot resist pointing  out  that  Mark  Twain,  by  linear
03800	projections  of  the  shortening  of  the  Mississippi river over the
03900	previous 100 years, predicted that the river would  be  all  gone  in
04000	another   900   years.      Shortly  after  Mark  Twain's  time,  the
04100	introduction of exponential projection vastly improved the technology
04200	of  generating  nonsensical  predictions,  but think how gratified he
04300	would have been, had he only lived  to  see  the  use  of  non-linear
04400	differential equations and computers for this purpose.
04500	
04600	John McCarthy
04700	Computer Science Department
04800	Stanford, California