[ RadSafe ] 100 years of cosmic rays mystery
royherren2005 at yahoo.com
Wed Aug 1 01:09:22 CDT 2012
100 years of cosmic rays mystery
Posted On: July 31, 2012 - 11:30pm
As physicists gather in early August to celebrate a century since the initial
discovery of cosmic rays, Alan Watson, emeritus professor of physics at the
University of Leeds, explains how physicists have gradually revealed the nature
of these mysterious objects and examines the progress being made in
understanding where they come from.
It is now widely accepted that cosmic rays are the nuclei of atoms, from the
entire range of naturally occurring elements, that travel at near-light-speeds
for millions of years before reaching Earth. However, identifying the source of
cosmic rays has proved to be a very difficult task.
The Pierre Auger Observatory – a 3000 km2 site in Argentina – is one of many
institutions around the world scouring the universe for the source of cosmic
rays and currently has 1600 Cherenkov detectors in operation, each looking to
find the source of cosmic-ray showers with extremely high energies.
This is in massive contrast to the techniques used by Austrian scientist Victor
Hess, who was the first to discover cosmic rays on 7 August 1912 by travelling
5000 m above ground in a hot-air balloon. He was awarded the Nobel Prize for
Physics in 1936 for his efforts.
The story of cosmic rays started in the 1780s when French physicist
Charles-Augustin de Coulomb noticed that an electrically charged sphere
spontaneously lost its charge, which at the time was strange as scientists
believed that air was an insulator, rather than a conductor.
Further investigations showed that air became a conductor when the molecules
were ionized by charged particles or X-rays.
The source of these charged particles puzzled scientists as experiments revealed
that objects were losing their charge even when shielded by a large volume of
lead, which was known to block X-rays and other radioactive sources.
Hess was the first to discover that the ionization of air was three times
greater at high altitudes than it was at ground level, leading him to conclude
that there was a very large source of radiation penetrating our atmosphere from
In this feature, Watson states that there is an unexpected benefit stemming from
Hess's original cosmic-ray research: the designer of the communications system
at the Pierre Auger Observatory has used the same sophisticated software to
build a radio-based signalling system that now extends over 700 km of the
single-track train line in the Scottish Highlands.
"The safety and reliability that rail travellers now enjoy while passing by
lochs and through glens is a benefit from Hess's daring flight a century ago
that surely he could never have foreseen," Watson writes.
Source: Institute of Physics
More information about the RadSafe