﻿198 
  ANNUAIi 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  the 
  atom 
  into 
  a 
  single 
  monochromatic 
  ether 
  wave 
  of 
  a 
  frequency 
  

   corresponding 
  to 
  the 
  sum 
  of 
  the 
  two 
  electron 
  jumps. 
  In 
  a 
  word, 
  

   of 
  the 
  process 
  by 
  which 
  an 
  ether 
  wave 
  is 
  born 
  we 
  know 
  only 
  this 
  

   much, 
  that 
  every 
  atomic 
  shudder 
  (change 
  in 
  energy) 
  of 
  whatever 
  

   sort 
  seems 
  to 
  become 
  integrated 
  into 
  a 
  monochromatic 
  ether 
  wave, 
  

   the 
  frequency 
  of 
  which 
  is 
  computable 
  from 
  hv—E^—E^^ 
  E^ 
  being 
  

   the 
  atomic 
  energy 
  before 
  the 
  shudder 
  and 
  E^ 
  that 
  after 
  it, 
  so 
  far 
  have 
  

   we 
  got 
  from 
  the 
  simple 
  mechanical 
  picture 
  of 
  a 
  little 
  electrical 
  

   vibrating 
  tuning 
  fork 
  sending 
  off 
  waves 
  into 
  the 
  ether 
  synchronously 
  

   with 
  its 
  own 
  vibration. 
  Both 
  the 
  mode 
  of 
  birth 
  of 
  an 
  ether 
  wave 
  

   l>y 
  an 
  atom 
  and 
  its 
  mode 
  of 
  transmission 
  from 
  star 
  to 
  star 
  after 
  

   birth 
  are 
  still 
  almost 
  complete 
  mysteries. 
  

  

  I 
  shall 
  mention 
  but 
  one 
  more 
  of 
  the 
  large 
  category 
  of 
  discoveries 
  

   constituting 
  twentieth 
  century 
  physics. 
  It 
  is 
  perhaps 
  the 
  most 
  

   striking 
  and 
  revolutionary 
  of 
  them 
  all. 
  The 
  discovery 
  that 
  the 
  

   very 
  foundations 
  of 
  mechanics 
  when 
  looked 
  at 
  microscopically 
  are 
  

   unsound, 
  that 
  apparently 
  all 
  periodic 
  motions 
  are 
  resolvable 
  into 
  

   circular 
  and 
  linear 
  coordinates 
  which 
  can 
  not 
  progress 
  continuously 
  

   as 
  demanded 
  by 
  the 
  Newtonian 
  laws, 
  but 
  are 
  built 
  up 
  out 
  of 
  definite 
  

   unitary 
  elements; 
  specifically, 
  that 
  a 
  body 
  rotating 
  in 
  a 
  circle 
  can 
  

   possess 
  only 
  such 
  angular 
  momenta 
  as 
  are 
  exact 
  multiples 
  of 
  a 
  

  

  universal 
  unit 
  of 
  angular 
  momentum, 
  viz, 
  ^r— 
  '. 
  This 
  unitary 
  fine 
  

  

  structure 
  in 
  motion, 
  like 
  the 
  unitary 
  fine 
  structure 
  in 
  electricity, 
  

   we 
  had 
  never 
  discovered 
  nor 
  even 
  dreamed 
  of 
  until 
  this 
  century, 
  

   because 
  we 
  had 
  never 
  experimented 
  upon 
  small 
  enough 
  angular 
  

   momenta 
  on 
  the 
  one 
  hand, 
  electrostatic 
  charges 
  on 
  the 
  other, 
  to 
  see 
  

   that 
  each 
  had 
  in 
  fact 
  a 
  granular 
  structure. 
  Wlien 
  one 
  is 
  weighing 
  

   sand 
  by 
  the 
  ton 
  it 
  has 
  for 
  him 
  no 
  granular 
  character. 
  It 
  is 
  only 
  

   when 
  he 
  begins 
  to 
  weigh 
  quantities 
  of 
  the 
  size 
  of 
  individual 
  grains 
  

   that 
  he 
  sees 
  it 
  to 
  be 
  granular. 
  That 
  periodic 
  motion 
  itself 
  has 
  such 
  

   a 
  granular 
  nature 
  is 
  one 
  of 
  the 
  most 
  amazing 
  experimental 
  discoveries 
  

   of 
  our 
  century. 
  We 
  can 
  still 
  look 
  with 
  a 
  sense 
  of 
  wonder 
  and 
  

   mystery 
  and 
  reverence 
  upon 
  the 
  fundamental 
  elements 
  of 
  the 
  physical 
  

   world 
  as 
  they 
  have 
  been 
  partially 
  revealed 
  to 
  us 
  in 
  this 
  century. 
  

   The 
  childish 
  mechanical 
  conceptions 
  of 
  the 
  nineteenth 
  century 
  are 
  

   now 
  grotesquely 
  inadequate. 
  

  

  We 
  have 
  now 
  no 
  one 
  consistent 
  scheme 
  of 
  interpretation 
  of 
  physi- 
  

   cal 
  phenomena 
  and 
  we 
  have 
  become 
  wise 
  enough 
  to 
  see 
  and 
  to 
  admit 
  

   that 
  we 
  have 
  none. 
  We 
  use 
  the 
  wave 
  theory, 
  for 
  example, 
  where 
  

   it 
  works; 
  we 
  use 
  the 
  quantum 
  theory 
  where 
  it 
  works, 
  and 
  we 
  try 
  

   to 
  bridge 
  the 
  gap 
  between 
  the 
  two 
  apparently 
  contradictory 
  theories 
  

   in 
  purely 
  formal 
  fashion 
  by 
  what 
  we 
  call 
  the 
  correspondence 
  prin- 
  

   ciple. 
  It 
  is 
  true 
  that 
  we 
  are 
  slowly 
  learning 
  more 
  of 
  the 
  rules 
  in 
  

  

  