﻿Fundamental 
  Laics 
  of 
  Matter 
  and 
  Energy. 
  Ill 
  

  

  If 
  we 
  assume 
  an 
  aether 
  pervading 
  space, 
  and 
  assume 
  that 
  

   this 
  aether 
  possesses 
  no 
  mass 
  except 
  when 
  it 
  moves 
  with 
  the 
  

   velocity 
  of 
  light, 
  it 
  is 
  obvious 
  that 
  an 
  asther 
  drift 
  could 
  in 
  no 
  

   way 
  affect 
  a 
  beam 
  of 
  radiation 
  nor 
  could 
  it 
  be 
  detected 
  by 
  

   any 
  mechanical 
  means. 
  If 
  we 
  are 
  to 
  assume 
  such 
  an 
  aether 
  

   we 
  may 
  as 
  well 
  assume 
  it 
  to 
  be 
  at 
  rest. 
  

  

  The 
  question 
  whether 
  a 
  method 
  is 
  conceivable 
  by 
  which 
  

   absolute 
  motion 
  in 
  space 
  may 
  be 
  distinguished 
  from 
  relative 
  

   motion 
  must 
  be 
  answered 
  definitely 
  in 
  the 
  affirmative 
  by 
  one 
  

   who 
  accepts 
  the 
  above 
  equations 
  of 
  non-Newtonian 
  mechanics. 
  

   A 
  body 
  is 
  absolutely 
  at 
  rest 
  when 
  any 
  motion 
  imparted 
  to 
  it 
  

   increases 
  its 
  mass, 
  or 
  when 
  a 
  certain 
  force 
  will 
  give 
  it 
  the 
  

   same 
  acceleration 
  in 
  any 
  direction. 
  It 
  is 
  true 
  that 
  meta- 
  

   physicians 
  hold 
  that 
  in 
  the 
  strictest 
  sense 
  absolute 
  motion 
  is 
  

   not 
  only 
  unknowable 
  but 
  unthinkable, 
  but 
  we 
  may 
  say 
  at 
  

   least 
  that 
  the 
  above 
  method 
  permits 
  theoretically 
  the 
  detection 
  

   of 
  absolute 
  translational 
  motion 
  in 
  the 
  same 
  sense 
  that 
  a 
  

   study 
  of 
  centrifugal 
  forces 
  enables 
  us 
  to 
  detect 
  absolute 
  

   rotational 
  motion. 
  

  

  Summary. 
  

  

  It 
  is 
  postulated 
  that 
  the 
  energy 
  and 
  momentum 
  of 
  a 
  beam 
  

   of 
  radiation 
  are 
  due 
  to 
  a 
  mass 
  moving 
  with 
  the 
  velocity 
  of 
  

   light. 
  

  

  From 
  this 
  postulate 
  alone 
  it 
  is 
  shown 
  that 
  the 
  mass 
  of 
  a 
  

   body 
  depends 
  upon 
  its 
  energy 
  content. 
  It 
  is 
  therefore 
  

   necessary 
  to 
  replace 
  that 
  axiom 
  of 
  Newtonian 
  mechanics 
  

   according 
  to 
  which 
  the 
  mass 
  of 
  a 
  body 
  is 
  independent 
  of 
  its 
  

   velocity, 
  by 
  one 
  which 
  makes 
  the 
  mass 
  increase 
  with 
  the 
  

   kinetic 
  energy. 
  

  

  Retaining 
  all 
  the 
  other 
  axioms 
  of 
  Newtonian 
  mechanics 
  

   and 
  assuming 
  the 
  conservation 
  laws 
  of 
  mass, 
  energy, 
  and 
  

   momentum, 
  a 
  new 
  system 
  of 
  mechanics 
  is 
  constructed. 
  

  

  In 
  this 
  system 
  momentum 
  is 
  mv, 
  kinetic 
  energy 
  varies 
  

   between 
  1/2 
  mv 
  2 
  at 
  low 
  velocity 
  and 
  mv 
  2 
  at 
  the 
  velocity 
  of 
  

   light, 
  while 
  the 
  mass 
  of 
  a 
  body 
  is 
  a 
  function 
  of 
  the 
  velocity 
  

   and 
  becomes 
  infinite 
  at 
  the 
  velocity 
  of 
  light. 
  The 
  equation 
  

   obtained 
  agrees 
  with 
  the 
  experiments 
  of 
  Kaufmann 
  on 
  the 
  

   relation 
  between 
  the 
  mass 
  of 
  an 
  electron 
  and 
  its 
  velocity. 
  

   It 
  is, 
  moreover, 
  strikingly 
  similar 
  to 
  the 
  equations 
  that 
  have 
  

   been 
  obtained 
  for 
  electromagnetic 
  mass. 
  

  

  The 
  new 
  view 
  leads 
  to 
  an 
  unusual 
  conception 
  of 
  the 
  nature 
  

   of 
  light. 
  It 
  offers 
  theoretically 
  a 
  method 
  of 
  distinguishing 
  

   between 
  absolute 
  and 
  relative 
  motion. 
  

  

  Research 
  Laboratory 
  of 
  Physical 
  Chemistry, 
  

  

  Massachusetts 
  Institute 
  of 
  Technology, 
  

  

  May 
  14, 
  1908. 
  

  

  