Table 852 6 4g 



TABLE 852. — Cosmic Rays 

 (Millikan, Cameron, Phys. Rev., 31, 921, 1928; 32, 533, 1928.) 



The measurements on the absorption coefficients for the cosmic rays indicate a complex 

 set of entering rays which may be analyzed into separate rays with mean absorption 

 coefficients O) per meter of water of 0.02, 0.04, 0.08, and 0.30. 



Formation of He nucleus from hydrogen : From Einstein's equation and Aston's curve 

 (Table 851) the loss of mass in the formation in a single act of the nucleus of He from 

 four -f- electrons and two — electrons is 4 X 1.00778 — 4 X 1.00054= 0.029 g/g-atom, and 

 the radiant energy released each time this act occurs is 



(0.029 X 9 X io 20 )/ (6.062 X io 23 ) = 4.3 X 10- 5 ergs. 



"= (4-3 X IO' 5 )/ (6.547 X io" 27 ) =6.57 X io' 21 , \ — 0.00046 A. From Dirac's relativity- 

 quantum-mechanics formula n = 0.30 per meter H 2 0. 



Oxygen from hydrogen: 16X0.00778 = 0.1245 g/g-atom ^ = 0.074 per m H 2 0. 



Nitrogen " 0.108 g/g-atom =0.086. 



Mean of these two corresponds to 0.08. 



Silicon gives /*= 0.041. Iron " ^ = 0.019. 



So that the observed /j. of the cosmic ray may correspond to the creation from hydrogen 

 of He (/* = 30), O (.08), Si (.04) and Fe (.02). 



Cosmic rays (A. H. Compton, Phys. Rev., 43, 387, 1933). — Intensity vs. altitude curves 

 indicate not only a rapid increase in ionization intensity with altitude but also that at each 

 alt. the intensity is greater for high lat. than near the Equator. At sea-level the intens. 

 at high lat. is 14% greater than at Equator ; at 2000 m alt., 22%, at 4360 m, 33% greater. 

 With arbitrary constants corresponding to 1.605 ions due to rays unaffected by the earth's 

 magnetic field (neutral rays or electrons of energies > 4 X io 10 electron-volts), and a 

 band of electrons approaching the earth with energies between 0.5 X io 1 * and 1.3 X io 10 

 electron-volts reaching the earth at lat. > 50° and producing 0.235 ion, but failing to 

 reach the earth at the Equator, Compton's observations will bear out the theory of 

 Lemaitre and Vallarta (Phys. Rev., 42, 914, 1932). The extra component appearing at 

 high lat. is more rapidly absorbed than the main body of rays. This would be anticipated 

 if rays unaffected by earth's magnetic field were of electrons of greater energy ; or a 

 uniform background due to neutral rays such as photons, neutrons, or high speed neutral 

 atoms. Average intensity lat. o° to 22 , sea-level, 1.620 ±0.006 ions per cm per sec; 

 lat. > 48 , 1.839 ± 0.006 ions. 



Cosmic rays (Millikan, Etat actuel de nos connaissances sur le lieu et la mode de pro- 

 duction des Rayons Cosmiques, Congres international d'Electricite, 1932; Phys. Rev., 43, 

 661, 1933; 43, 695, 1933; Science, 77< 494. 1933; 77~ May 5, 1933).— Most distinctive 

 results: (A) Ionization-altitude curve (to 18 km or 92% through the atmosphere) 

 does not rise exponentially clear to top with apparent absorption coefficient about 0.6 per 

 m H 2 (all observers get this, say 5 to 9 km) but shows a marked decrease 9 km to top 

 (about 12 km), actually becoming concave downward. This is inconsistent with (1) 

 incoming rays primarily of charged particles, (2) photons in complete equilibrium with 

 their secondaries, (3) rays of the penetrating power of 7 rays or rays between these and 

 the least energetic cosmic rays. They show non-ionizing prirnary entering rays not yet 

 in equilibrium with secondaries. 



The rays show a rapid softening with altitude (essentially the same in temperate and 

 equatorial latitudes); best interpreted by cosmic photon bands of widely differing pene- 

 trating powers as from the production of He, O, Si, Fe, etc. More than f of the cosmic 

 rays at 7.6 km have energy < 350,000,000 volts. Millikan considers that the " cosmic rays " 

 found at low altitudes are secondaries formed in the earth's atmosphere by collisions of 

 photons with air atoms. Anderson has caught the cosmic rays, which cannot themselves 

 be photographed, in the act of smashing atoms, setting loose + and — charged particles. 

 So all but a small fraction of the cosmic rays at sea-level are secondaries produced in the 

 earth's atmosphere. 

 Smithsonian Tables 



