A Caltech Library Service

The origin of the cosmic rays

Millikan, R. A. and Cameron, G. H. (1928) The origin of the cosmic rays. Physical Review, 32 (4). pp. 533-557. ISSN 0031-899X. doi:10.1103/PhysRev.32.533.

See Usage Policy.


Use this Persistent URL to link to this item:


Maximum energy released by atomic-disintegration (radioactivity.)—From Einstein's equation Mc2=E and Aston's curve the maximum possible energy that can be released in radioactive changes can be computed. The theoretical and experimental values are in satisfactory agreement. Energy released in step-by-step atom-building.—No step-by-step atom-building process can produce rays as penetrating as the observed cosmic rays. The absence of the radiations corresponding to such step-by-step processes probably means that atom-building does not in general occur in this way. The creation of helium out of hydrogen.—About 80 percent of the observed cosmic rays appear to be due to the act corresponding to the sudden union of four positive and two negative electrons into the nucleus of the atom of helium. This produces a cosmic ray of absorption coefficient μ=0.30 per meter of water. The creation of oxygen and silicon out of hydrogen.—The observed cosmic rays of absorption coefficients μ=0.08 and μ=0.04 appear to be produced by the sudden building of positive and negative electrons into atoms of oxygen and silicon, the former act giving rise to a ray of absorption coefficient μ=0.08, the latter to μ=0.04. This last is a definitely observed ray having an energy corresponding to the fall of an electron through 216,000,000 volts. Possible rays due to the creation of iron and to the annihilation of hydrogen.—The cosmic-ray indications are reconcilable with the view that iron is produced by the union in a single act of positive and negative electrons into the atom of iron, but the cosmic rays show no direct indications of the transformation of the whole mass of the hydrogen atom into radiation. Synthetic cosmic-ray curves.—The observed cosmic-ray curve can be built up fairly satisfactorily by the assumption that the relative intensities of the cosmic rays reaching the earth's atmosphere are proportional to the abundance of the common elements in meteorites and the earth's crust, 96 percent of these bodies being made of the four elements, oxygen, magnesium, silicon and iron. The kinetics of atom-building.—While the kinetics of atom-building are more bothersome than the thermodynamics, with suitable assumptions, presented herewith, they may not offer wholly insuperable difficulties. The place of origin of the cosmic rays.—Evidence is presented to show that cosmic rays do not originate in the stars, but only in the depths of space where temperature and densities are practically zero. Cosmic rays and the Second Law of Thermodynamics.—The observed properties of cosmic rays, indicating that the creation of the common elements occurs only in interstellar or intergalactic space, suggest the possibility of avoiding the "wärmetod," and of regarding the universe as already in "the steady state."

Item Type:Article
Related URLs:
URLURL TypeDescription
Additional Information:©1928 The American Physical Society. Received 9 July 1928.
Issue or Number:4
Record Number:CaltechAUTHORS:MILpr28b
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2317
Deposited By: Tony Diaz
Deposited On:27 Mar 2006
Last Modified:08 Nov 2021 19:46

Repository Staff Only: item control page