﻿PHYSICS 
  OF 
  THE 
  UNIVERSE 
  JEANS 
  163 
  

  

  disintegration 
  in 
  the 
  same 
  way 
  as 
  the 
  heavy 
  radioactive 
  atoms, 
  the 
  

   nuclei 
  of 
  these 
  also 
  are 
  of 
  composite 
  structure, 
  and 
  can 
  be 
  broken 
  up 
  

   by 
  artificial 
  means. 
  In 
  1920, 
  Rutherford 
  succeeded 
  in 
  breaking 
  up 
  

   the 
  nuclei 
  of 
  atoms 
  of 
  oxygen 
  and 
  nitrogen 
  by 
  bombarding 
  them 
  with 
  

   swiftly 
  moving 
  a-particles. 
  

  

  The 
  success 
  of 
  this 
  experiment 
  led 
  to 
  the 
  hypothesis, 
  which 
  has 
  

   not 
  yet 
  been 
  established 
  beyond 
  all 
  possibility 
  of 
  doubt, 
  that 
  the 
  

   whole 
  universe 
  is 
  built 
  up 
  of 
  only 
  two 
  kinds 
  of 
  ultimate 
  bricks, 
  namely, 
  

   electrons 
  and 
  protons. 
  Each 
  proton 
  carries 
  a 
  positive 
  charge 
  which 
  

   is 
  exactly 
  equal 
  in 
  amount 
  to 
  the 
  negative 
  charge 
  carried 
  by 
  an 
  

   electron. 
  The 
  protons 
  are 
  supposed 
  to 
  be 
  identical 
  with 
  the 
  nucleus 
  

   of 
  the 
  hydrogen 
  atom; 
  all 
  other 
  nuclei 
  are 
  supposed 
  to 
  consist 
  of 
  

   closely 
  packed 
  structures 
  of 
  protons 
  and 
  electrons. 
  

  

  In 
  addition 
  to 
  containing 
  material 
  electrons 
  and 
  protons, 
  the 
  atom 
  

   contains 
  yet 
  a 
  third 
  ingredient, 
  namely, 
  electromagnetic 
  energy. 
  

   Modern 
  electromagnetic 
  theory 
  shows 
  that 
  all 
  radiation 
  carries 
  mass 
  

   about 
  with 
  it, 
  one 
  gram 
  of 
  mass 
  being 
  associated 
  with 
  9X10^° 
  ergs 
  or 
  

   2.15 
  X 
  10'^ 
  calories 
  of 
  radiation. 
  As 
  a 
  necessary 
  consequence, 
  any 
  

   substance 
  which 
  is 
  emitting 
  radiation 
  must 
  also 
  be 
  losing 
  mass; 
  the 
  

   spontaneous 
  disintegration 
  of 
  any 
  radioactive 
  substance 
  involves 
  a 
  

   spontaneous 
  decrease 
  of 
  weight. 
  The 
  ultimate 
  fate 
  of 
  a 
  gram 
  of 
  

   uranium 
  may 
  be 
  expressed 
  by 
  the 
  equation: 
  

  

  [0.8653 
  gm. 
  lead. 
  

   1 
  gram 
  uranium 
  = 
  ] 
  0.1345 
  gm. 
  helium. 
  

  

  [0.0002 
  gm. 
  radiation. 
  

  

  Stated 
  in 
  a 
  very 
  general 
  form, 
  the 
  phenomenon 
  of 
  radioactivity 
  

   may 
  be 
  described 
  as 
  a 
  transformation 
  of 
  material 
  mass 
  into 
  radiation 
  

   or, 
  to 
  put 
  it 
  slightly 
  differently, 
  as 
  the 
  liberation 
  of 
  radiation 
  by 
  the 
  

   destruction 
  of 
  material 
  mass. 
  Where 
  4,000 
  gm. 
  of 
  matter 
  originally 
  

   existed, 
  only 
  3,999 
  gm. 
  now 
  remain, 
  the 
  remaining 
  gram 
  having 
  

   gone 
  off 
  in 
  the 
  form 
  of 
  radiation. 
  

  

  Yet, 
  the 
  3,999 
  gm. 
  of 
  lead 
  and 
  helium 
  contain 
  precisely 
  the 
  same 
  

   protons 
  and 
  electrons 
  as 
  the 
  original 
  4,000 
  gm. 
  of 
  uranium; 
  we 
  may 
  

   then, 
  say 
  that 
  the 
  4,000 
  gm. 
  of 
  uranium 
  consisted 
  of 
  these 
  electrons 
  

   and 
  protons 
  together 
  with 
  1 
  gm. 
  of 
  bottled-up 
  electromagnetic 
  

   energy 
  which 
  has 
  since 
  escaped 
  in 
  the 
  form 
  of 
  radiation. 
  

  

  So 
  far 
  as 
  terrestrial 
  experience 
  goes, 
  this 
  dissolution 
  of 
  mass 
  into 
  

   radiation 
  is 
  entirely 
  a 
  one-way 
  process. 
  Terrestrial 
  rocks 
  provide 
  

   abundant 
  evidence 
  of 
  uranium 
  having 
  continuously 
  broken 
  up 
  into 
  

   lead, 
  helium, 
  and 
  radiation 
  for 
  the 
  past 
  thousand 
  million 
  years 
  or 
  more, 
  

   but 
  there 
  is 
  no 
  evidence 
  of 
  the 
  converse 
  process 
  ever 
  having 
  occurred. 
  

   We 
  must 
  suppose 
  that 
  there 
  is 
  less 
  uranium 
  on 
  earth 
  to-day 
  than 
  there 
  

   was 
  yesterday, 
  and 
  that 
  by 
  to-morrow 
  there 
  will 
  be 
  still 
  less. 
  As 
  a 
  

   consequence, 
  the 
  earth 
  each 
  day 
  radiates 
  away 
  a 
  little 
  more 
  heat 
  than 
  

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