﻿THE 
  EVOLUTION 
  OF 
  TWENTIETH 
  CENTUEY 
  PHYSICS 
  ^ 
  

  

  By 
  Robert 
  A. 
  Millikan 
  

  

  My 
  own 
  period 
  of 
  activity 
  in 
  the 
  intensive 
  pursuit 
  of 
  physics 
  

   happens 
  to 
  be 
  abnost 
  exactly 
  coincident 
  with 
  the 
  period 
  of 
  develop- 
  

   ment 
  of 
  what 
  we 
  may 
  call 
  modern 
  physics 
  as 
  distinct 
  from 
  nine- 
  

   teenth 
  century 
  physics; 
  so 
  that 
  I 
  am 
  in 
  the 
  rather 
  unusual 
  posi- 
  

   tion 
  of 
  being 
  able 
  to 
  relate, 
  from 
  my 
  own 
  experiences 
  and 
  entirely 
  

   without 
  reference 
  to 
  books, 
  when 
  and 
  how 
  the 
  changes 
  occurred, 
  

   how 
  some 
  of 
  the 
  actors 
  felt 
  and 
  thought 
  and 
  acted 
  in 
  the 
  presence 
  of 
  

   each 
  new 
  development, 
  and 
  what 
  stupendous 
  shifts 
  in 
  viewpoint 
  have 
  

   been 
  brought 
  about. 
  This 
  is 
  my 
  excuse 
  for 
  making 
  this 
  paper 
  to 
  

   some 
  extent 
  a 
  personal 
  narrative. 
  

  

  The 
  transition 
  from 
  the 
  old 
  to 
  the 
  new 
  mode 
  of 
  thought 
  in 
  

   physics 
  was 
  probably 
  made 
  as 
  dramatically 
  in 
  my 
  case 
  as 
  in 
  that 
  

   of 
  anyone 
  in 
  the 
  world, 
  for 
  I 
  was 
  in 
  the 
  fortunate 
  position 
  of 
  hav- 
  

   ing 
  entered 
  the 
  field 
  just 
  three 
  years 
  before 
  the 
  end 
  of 
  the 
  com- 
  

   plete 
  dominance 
  of 
  nineteenth-century 
  modes 
  of 
  thought. 
  In 
  those 
  

   three 
  years 
  I 
  had 
  the 
  privilege 
  of 
  personally 
  meeting 
  and 
  hearing 
  

   lectures 
  by 
  the 
  most 
  outstanding 
  creators 
  of 
  nineteeth-century 
  

   physics 
  — 
  Kelvin, 
  Helmholtz, 
  Boltzman, 
  Poincare, 
  Rayleigh, 
  Van't 
  

   Hoff, 
  Michelson, 
  Ostwald, 
  Lorentz 
  — 
  every 
  one 
  of 
  whom 
  I 
  met 
  and 
  

   heard 
  between 
  1892 
  and 
  1896. 
  In 
  one 
  of 
  these 
  lectures 
  I 
  listened 
  

   with 
  rapt 
  attention 
  to 
  the 
  expression 
  of 
  a 
  point 
  of 
  view 
  which 
  was 
  

   undoubtedly 
  held 
  by 
  most 
  of 
  them 
  — 
  indeed 
  by 
  practically 
  all 
  physic- 
  

   ists 
  of 
  that 
  epoch 
  ; 
  for 
  it 
  had 
  been 
  given 
  expression 
  more 
  than 
  once 
  by 
  

   the 
  most 
  distinguished 
  men 
  of 
  the 
  nineteenth 
  century. 
  

  

  The 
  speaker 
  had 
  reviewed, 
  first 
  the 
  establishment 
  and 
  definite 
  

   proof 
  of 
  the 
  principles 
  of 
  mechanics 
  during 
  the 
  seventeenth 
  and 
  

   eighteenth 
  centuries 
  culminating 
  in 
  La 
  Place's 
  great 
  " 
  Mecanique 
  

   Celeste 
  " 
  ; 
  then 
  he 
  had 
  turned 
  to 
  the 
  wonderfully 
  complete 
  verifica- 
  

   tion 
  of 
  the 
  wave 
  theory 
  of 
  light 
  by 
  Young, 
  Fresnel, 
  and 
  others 
  between 
  

   1800 
  and 
  1850, 
  experiments 
  which 
  laid 
  secure 
  foundations 
  for 
  the 
  

   later 
  structure 
  known 
  as 
  the 
  physics 
  of 
  the 
  ether, 
  one 
  of 
  the 
  most 
  beau- 
  

  

  1 
  This 
  lecture 
  (introductory 
  parasraplis 
  omitted) 
  forms 
  Tart 
  I 
  of 
  a 
  volume 
  entitled 
  

   " 
  Evolution 
  in 
  Science 
  and 
  Religion," 
  Iiy 
  R. 
  A. 
  Millikan, 
  published 
  by 
  the 
  Yale 
  University 
  

   Press, 
  copyright 
  1927 
  ; 
  here 
  reprinted 
  by 
  permission. 
  

  

  191 
  

  

  