﻿PHYSICS 
  OF 
  THE 
  UNIVERSE 
  — 
  JEANS 
  175 
  

  

  know 
  the 
  ancestry 
  of 
  terrestrial 
  radium, 
  whereas 
  we 
  do 
  not 
  know 
  that 
  

   of 
  solar 
  uranium. 
  But 
  ancestry 
  there 
  must 
  be, 
  so 
  that 
  we 
  are 
  led 
  

   directly 
  to 
  the 
  conjecture 
  that 
  the 
  sun 
  must 
  have 
  contained, 
  and 
  pre- 
  

   sumably 
  must 
  still 
  contain, 
  atoms 
  of 
  atomic 
  weight 
  greater 
  than 
  that 
  

   of 
  uranium; 
  astronomical 
  evidence 
  leads 
  independently 
  to 
  the 
  same 
  

   conclusion. 
  We 
  are 
  led 
  to 
  contemplate 
  terrestrial 
  uranium 
  merely 
  as 
  

   the 
  present 
  generation 
  of 
  an 
  ancestry 
  that 
  extends 
  we 
  know 
  not 
  how 
  

   far 
  back. 
  The 
  complete 
  series 
  of 
  chemical 
  elements 
  contains 
  elements 
  

   of 
  greater 
  atomic 
  weight 
  than 
  uranium, 
  but 
  all 
  such 
  have, 
  to 
  the 
  best 
  

   of 
  our 
  knowledge, 
  vanished 
  from 
  the 
  earth, 
  as 
  uranium 
  also 
  is 
  destined 
  

   to 
  do 
  in 
  time. 
  

  

  Table 
  III 
  above 
  shows 
  the 
  wave 
  lengths 
  of 
  the 
  radiation 
  necessary 
  

   to 
  effect 
  various 
  atomic 
  transformations. 
  The 
  last 
  two 
  columns 
  show 
  

   the 
  corresponding 
  temperatures, 
  and 
  the 
  places, 
  so 
  far 
  as 
  we 
  know, 
  

   where 
  this 
  temperature 
  is 
  to 
  be 
  found. 
  In 
  places 
  where 
  the 
  temper- 
  

   ature 
  is 
  far 
  below 
  that 
  mentioned 
  in 
  the 
  last 
  column 
  but 
  one, 
  the 
  trans- 
  

   formation 
  in 
  question 
  can 
  not 
  be 
  affected 
  by 
  heat, 
  and 
  so 
  can 
  only 
  

   occur 
  spontaneously. 
  Thus 
  it 
  is 
  entirely 
  a 
  one-way 
  process. 
  The 
  

   available 
  radiation 
  is 
  not 
  of 
  the 
  right 
  wave 
  length 
  to 
  work 
  the 
  atomic 
  

   slot 
  machine, 
  so 
  that 
  the 
  atoms, 
  absorbing 
  no 
  energy 
  from 
  the 
  sur- 
  

   rounding 
  radiation, 
  are 
  continually 
  slipping 
  back 
  into 
  states 
  of 
  lower 
  

   energy, 
  if 
  such 
  exist; 
  they 
  continually 
  transform 
  their 
  mass 
  into 
  radia- 
  

   tion, 
  while 
  the 
  converse 
  transformation 
  of 
  radiation 
  into 
  mass 
  can 
  

   not 
  occur. 
  

  

  For 
  the 
  sake 
  of 
  completeness, 
  the 
  table 
  has 
  been 
  extended 
  so 
  as 
  to 
  

   include 
  certain 
  other 
  phenomena, 
  not 
  so 
  far 
  discussed, 
  to 
  which 
  we 
  

   now 
  turn. 
  

  

  THE 
  ANNIHILATION 
  OF 
  MATTER 
  

  

  Every 
  square 
  centimeter 
  of 
  the 
  sun's 
  surface 
  discharges 
  radiation 
  

   out 
  into 
  space 
  at 
  the 
  rate 
  of 
  about 
  1,500 
  calories 
  a 
  second, 
  from 
  which 
  

   we 
  can 
  calculate 
  that 
  the 
  sun's 
  total 
  mass 
  is 
  diminishing 
  at 
  about 
  

   250,000,000 
  tons 
  a 
  minute. 
  Whereas 
  the 
  flow 
  of 
  mass 
  from 
  the 
  earth's 
  

   surface, 
  a 
  total 
  loss 
  of 
  about 
  an 
  ounce 
  a 
  minute, 
  is 
  about 
  equal 
  to 
  the 
  

   flow 
  of 
  water 
  from 
  a 
  dripping 
  tap, 
  the 
  flow 
  of 
  mass 
  from 
  the 
  sun's 
  sur- 
  

   face 
  is 
  about 
  650 
  times 
  the 
  flow 
  of 
  water 
  over 
  Niagara. 
  Many 
  stars 
  

   lose 
  mass 
  even 
  more 
  rapidly 
  ; 
  S. 
  Doradus 
  loses 
  mass 
  at 
  the 
  rate 
  of 
  about 
  

   200,000,000 
  Niagaras. 
  The 
  earth's 
  loss 
  of 
  mass 
  is 
  readily 
  explained 
  

   in 
  terms 
  of 
  radioactive 
  disintegration, 
  but 
  this 
  fails 
  entirely 
  to 
  explain 
  

   the 
  enormously 
  greater 
  loss 
  experienced 
  by 
  the 
  sun. 
  Furthermore, 
  

   the 
  earth's 
  loss 
  of 
  mass 
  is 
  probably, 
  replaced 
  many 
  times 
  over 
  by 
  falls 
  

   of 
  meteors 
  and 
  cosmic 
  dust, 
  but 
  no 
  one 
  has 
  ever 
  suspected 
  or 
  suggested 
  

   any 
  source 
  of 
  replenishment 
  of 
  the 
  masses 
  of 
  the 
  sun 
  and 
  stars 
  which 
  

   is 
  at 
  all 
  comparable 
  with 
  their 
  known 
  loss. 
  

  

  