﻿176 
  ANNUAL 
  EEPORT 
  SMITHSONIAN 
  INSTITUTION, 
  19 
  2 
  9 
  

  

  Thus 
  the 
  sun's 
  loss 
  of 
  mass 
  is 
  cumulative 
  and 
  has 
  in 
  all 
  probability 
  

   gone 
  on 
  at 
  its 
  present, 
  or 
  at 
  an 
  even 
  greater, 
  rate 
  throughout 
  the 
  

   whole 
  of 
  its 
  vast 
  age 
  of 
  some 
  seven 
  million 
  million 
  years. 
  Indeed, 
  

   astronomical 
  evidence 
  makes 
  it 
  fairly 
  certain 
  that 
  younger 
  stars 
  

   radiate 
  more 
  energetically 
  than 
  older 
  stars. 
  When 
  allowance 
  is 
  

   made 
  for 
  this, 
  it 
  is 
  found 
  that 
  the 
  sun 
  must 
  have 
  radiated 
  many 
  

   times 
  its 
  present 
  mass 
  during 
  its 
  life 
  of 
  seven 
  million 
  million 
  years; 
  

   it 
  must 
  have 
  been 
  many 
  times 
  as 
  massive 
  at 
  birth 
  as 
  it 
  is 
  now, 
  and 
  of 
  

   every 
  ton 
  it 
  originally 
  contained 
  only 
  a 
  few 
  hundredweight 
  remain 
  

   to-day. 
  Since 
  no 
  form 
  of 
  radioactive 
  disintegration 
  with 
  which 
  

   we 
  are 
  acquainted 
  results 
  in 
  such 
  a 
  diminution 
  of 
  mass 
  as 
  this, 
  we 
  

   are 
  forced 
  to 
  suppose 
  that 
  something 
  still 
  more 
  fundamental 
  is 
  respon- 
  

   sible 
  for 
  the 
  sun's 
  diminution 
  of 
  mass 
  and 
  emission 
  of 
  radiation. 
  

   Of 
  each 
  thousand 
  atoms 
  that 
  the 
  sun 
  contained 
  at 
  its 
  birth 
  only 
  a 
  

   few 
  dozen 
  remain 
  to-day, 
  and 
  we 
  can 
  only 
  conclude 
  that 
  all 
  the 
  rest 
  

   have 
  been 
  annihilated 
  and 
  their 
  mass 
  set 
  free 
  in 
  the 
  form 
  of 
  radiation. 
  

   This 
  transformation 
  of 
  atoms 
  into 
  radiation, 
  although 
  unknown 
  to 
  

   terrestrial 
  physics, 
  must 
  clearly 
  be 
  one 
  of 
  the 
  fundamental 
  physical 
  

   processes 
  of 
  the 
  universe. 
  

  

  THE 
  UNIVERSE 
  AS 
  A 
  HEAT-ENGINE 
  

  

  General 
  thermodynamical 
  theory 
  shows 
  that 
  every 
  natural 
  system 
  

   tends 
  to 
  move 
  toward 
  a 
  final 
  state 
  of 
  maximum 
  entropy 
  by 
  steps 
  

   such 
  that, 
  statistically 
  speaking, 
  the 
  entropy 
  increases 
  with 
  every 
  

   step. 
  In 
  calculating 
  this 
  entropy, 
  classical 
  thermodynamics 
  regarded 
  

   the 
  chemical 
  atoms 
  as 
  indivisible, 
  indestructible, 
  and 
  immutible; 
  

   the 
  system 
  consisted 
  merely 
  of 
  permanent 
  atoms 
  and 
  energy, 
  and 
  

   maximum 
  entropy 
  was 
  attained 
  when 
  this 
  energy 
  was 
  partitioned 
  

   between 
  the 
  kinetic 
  and 
  potential 
  energies 
  of 
  the 
  atoms 
  and 
  the 
  energy 
  

   of 
  radiation 
  traveling 
  freely 
  through 
  space, 
  in 
  such 
  a 
  way 
  that 
  no 
  

   possible 
  redistribution 
  could 
  make 
  the 
  entropy 
  greater. 
  

  

  Modern 
  knowledge 
  shows 
  this 
  scheme 
  of 
  thermodynamics 
  to 
  be 
  

   totally 
  inadequate. 
  So 
  far 
  from 
  atoms 
  being 
  the 
  eternal 
  unchange- 
  

   able 
  bricks 
  of 
  the 
  universe, 
  modern 
  science 
  finds 
  them 
  subject 
  not 
  

   only 
  to 
  constant 
  change, 
  but 
  also 
  to 
  total 
  destruction. 
  Not 
  only 
  do 
  

   their 
  nuclei 
  change 
  their 
  retinue 
  of 
  attendant 
  electrons, 
  but 
  they 
  them- 
  

   selves 
  both 
  crumble 
  away 
  into 
  simpler 
  nuclei, 
  and 
  dissolve 
  entirely 
  

   into 
  radiation. 
  Furthermore, 
  energy 
  can 
  reside 
  in 
  other 
  forms 
  than 
  

   those 
  just 
  enumerated; 
  it 
  can 
  be 
  used, 
  stored, 
  and 
  transformed 
  in 
  

   changing 
  electron 
  orbits 
  inside 
  the 
  atom, 
  in 
  breaking 
  up 
  atoms, 
  

   in 
  rearranging 
  and 
  breaking 
  up 
  the 
  atomic 
  nuclei 
  and 
  so 
  transmuting 
  

   the 
  elements; 
  it 
  can 
  be 
  liberated 
  by 
  the 
  complete 
  annihilation 
  of 
  mat- 
  

   ter. 
  Neither 
  total 
  energy 
  nor 
  total 
  mass 
  is 
  any 
  longer 
  constant; 
  the 
  

   conservation 
  both 
  of 
  mass 
  and 
  of 
  energy 
  has 
  disappeared 
  from 
  

   physics, 
  and 
  only 
  a 
  kind 
  of 
  sum 
  of 
  the 
  two 
  is 
  conserved. 
  

  

  