The World of Atom (Part VIII)



Chapter 41: The Discovery of Cosmic Rays (Viktor F. Hess 1883 – 1964)

Penetrating γ radiation from the earth’s radioactive material falls off very quickly with increasing height. Data from balloon flights showed that the intensity of the penetrating radiation increases with height. These rays appear to strike the earth in equal intensities from all directions of space, and with energies ranging up to a billion trillion electron volts, far larger than any other known energies in nature. Now we know that cosmic rays are mostly very energetic protons intermixed with small quantities of heavy positive ions and electrons and positrons. Data from the Fermi Space Telescope (2013) have been interpreted as evidence that a significant fraction of primary cosmic rays originates from the supernova explosions of stars. When these very energetic particles strike the earth’s atmosphere, they give rise to vast showers of other atomic and subatomic particles.

A large part of Cosmic Rays are protons, which are hydrogen ions. This is primary material substance stripped off of electromagnetic substance.

Chapter 42: The Cloud Chamber (Charles Thomson Rees Wilson 1869 – 1959)

The cloud chamber helps visualize the passage of ionizing radiation. It consists of a sealed environment containing a supersaturated vapor of water or alcohol. An energetic charged particle (for example, an alpha or beta particle) interacts with the gaseous mixture by knocking electrons off gas molecules via electrostatic forces during collisions, resulting in a trail of ionized gas particles. The resulting ions act as condensation centers around which a mist-like trail of small droplets form. These droplets are visible as a “cloud” track that persists for several seconds. These tracks have characteristic shapes. For example, an alpha particle track is thick and straight, while an electron track is wispy and shows more evidence of deflections by collisions. Cloud chamber played a prominent role in experimental particle physics from the 1920s to the 1950s. It led to the discoveries of the positron in 1932 and the muon in 1936.

This was an ingenious invention.



  1. Cosmic rays, a large part of which are very energetic protons, fill the outer space.
  2. The cloud chamber helps visualize the passage of ionizing radiation.

The outer space is not empty of substance.


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