﻿CUSMICAL 
  PHYSICS 
  JEANS 
  187 
  

  

  temperatures 
  close 
  up 
  to 
  the 
  maximum 
  for 
  their 
  mass. 
  This 
  is 
  in 
  

   actual 
  fact 
  found 
  to 
  be 
  the 
  case. 
  

  

  All 
  the 
  evidence 
  at 
  present 
  available 
  points 
  to 
  the 
  annihilation 
  of 
  

   matter 
  being 
  a 
  quantum 
  phenomenon 
  ; 
  possibly 
  it 
  represents 
  nothing 
  

   more 
  than 
  the 
  spontaneous 
  drop 
  of 
  an 
  electron 
  to 
  a 
  zero-quantum 
  

   orbit. 
  This 
  would 
  suggest 
  an 
  explanation 
  of 
  why 
  bare 
  nuclei 
  and 
  

   free 
  electrons 
  should 
  be 
  immune 
  from 
  annihilation, 
  and 
  hence 
  why 
  

   atoms 
  stripped 
  bare 
  of 
  electrons 
  can 
  not 
  generate 
  energy. 
  

  

  HIGHLY 
  PENETRATING 
  RADIATION 
  

  

  If 
  our 
  earth 
  exhibits 
  only 
  one 
  end 
  of 
  the 
  chain 
  of 
  chemical 
  ele- 
  

   ments, 
  where 
  shall 
  Ave 
  look 
  for 
  the 
  other 
  end? 
  Moving 
  backwards 
  

   along 
  the 
  evolutionary 
  sequence 
  we 
  come 
  to 
  younger 
  and 
  yet 
  younger 
  

   stars, 
  containing 
  elements 
  of 
  higher 
  and 
  higher 
  atomic 
  weight. 
  

   Passing 
  beyond 
  the 
  stars 
  altogether 
  we 
  come 
  to 
  the 
  nebulaj; 
  here 
  we 
  

   ought 
  to 
  find 
  the 
  elements 
  of 
  highest 
  atomic 
  weight 
  of 
  all, 
  and 
  the 
  

   matter 
  of 
  greatest 
  radiating 
  capacity. 
  

  

  Visually 
  the 
  nebulae 
  are 
  extremely 
  faint 
  objects; 
  their 
  emission 
  of 
  

   visual 
  radiation 
  per 
  unit 
  mass 
  is 
  only 
  about 
  equal 
  to 
  that 
  of 
  our 
  

   sun. 
  There 
  is, 
  however, 
  an 
  essential 
  difference 
  between 
  the 
  radiation 
  

   generated 
  in 
  the 
  stars 
  and 
  that 
  generated 
  in 
  the 
  nebulae. 
  Kadiation, 
  

   VN^hen 
  first 
  generated, 
  must 
  have 
  enormous 
  penetrating 
  power; 
  the 
  

   simultaneous 
  annihilation 
  of 
  a 
  single 
  electron 
  and 
  proton 
  produces 
  

   radiation 
  of 
  wave-length 
  only 
  1.3 
  X 
  10-^^ 
  cm. 
  The 
  high 
  penetrating 
  

   power 
  of 
  this 
  short 
  wave-length 
  radiation, 
  nevertheless, 
  only 
  suffices 
  

   to 
  carry 
  it 
  through 
  a 
  small 
  fraction 
  of 
  the 
  radius 
  of 
  a 
  star, 
  and 
  suc- 
  

   cessive 
  absorptions 
  and 
  remissions 
  soften 
  it, 
  by 
  a 
  sort 
  of 
  generalized 
  

   Compton 
  effect, 
  until 
  it 
  finally 
  emerges 
  from 
  the 
  surface 
  of 
  the 
  star 
  

   as 
  ordinary 
  temperature 
  radiation. 
  The 
  density 
  of 
  the 
  nebulae 
  is, 
  

   however, 
  so 
  much 
  lower 
  than 
  that 
  of 
  the 
  stars 
  that 
  similar 
  radiation, 
  

   when 
  generated 
  inside 
  a 
  nebula, 
  passes 
  almost 
  unchecked 
  directly 
  

   into 
  outer 
  space. 
  Here 
  and 
  there 
  the 
  radiation 
  may 
  devastate 
  iso- 
  

   lated 
  atoms 
  in 
  its 
  passage, 
  ejecting 
  a 
  few 
  million-volt 
  electrons 
  in 
  

   the 
  process, 
  but 
  the 
  majority 
  of 
  it 
  will 
  pass 
  on 
  unhindered 
  until 
  it 
  

   meets 
  a 
  medium 
  of 
  substantial 
  absorbing 
  powers. 
  Thus 
  we 
  should 
  

   expect 
  the 
  atmospheres 
  of 
  the 
  stars, 
  sun, 
  and 
  earth, 
  and 
  even 
  the 
  

   solid 
  body 
  of 
  the 
  earth, 
  to 
  be 
  under 
  continual 
  bombardment 
  by 
  

   highly-penetrating 
  radiation 
  of 
  nebular 
  origin. 
  

  

  Such 
  radiation 
  has 
  been 
  detected 
  in 
  the 
  earth's 
  atmosphere 
  by 
  

   Kolhorster, 
  Millikan, 
  and 
  many 
  others, 
  who 
  are 
  satisfied 
  that 
  it 
  is 
  of 
  

   extra-terrestrial 
  origin. 
  If 
  it 
  originated 
  in 
  the 
  stars, 
  the 
  amount 
  

   received 
  would 
  depend 
  largely 
  upon 
  the 
  position 
  of 
  the 
  sun. 
  As 
  it 
  

   does 
  not, 
  the 
  radiation 
  must 
  originate 
  in 
  nebulae 
  or 
  cosmic 
  masses 
  

   other 
  than 
  stars. 
  Quite 
  recently 
  (Nature, 
  October 
  9, 
  1926), 
  Kol- 
  

  

  