The Nobel Prize in Physics 1974
Martin Ryle, Antony Hewish
15 October 1974
The Royal Swedish
Academy of Sciences has awarded Professor Martin Ryle
and Professor Antony Hewish the 1974 Nobel Prize in
Physics. Professors Ryle and Hewish have been
awarded the Prize for their pioneering research in
radioastrophysics: Ryle for his observations and inventions, in
particular of the aperture-synthesis technique, and Hewish
for his decisive role in the discovery of pulsars.
THE PHYSICS OF THE STARS
Astrophysics, the science dealing with the physical properties of
the stars and the stellar systems, has developed rapidly during
recent decades. This is mainly due to new discoveries made with
radio astronomical methods. These methods are of vital importance
when making observations over cosmic distances, thousands of
millions of lightyears or more. It is essential that such
distances can be covered when trying to chart the development of
the universe. A light year is the distance that light travels in
one year. Light moves at a speed of 300 pillion metres per
second.
In contrast to visible light coming to us from the celestial
sphere, radio emission from other space can only be perceived
with the help of telescopes. Highly sensitive electronic
instruments amplify and handle the data-processing of the
signals.
SEVERAL SMALL TELESCOPES "FORM" ONE LARGE TELESCOPE
During the last twenty-five years, Martin Ryle has developed new
epochmaking telescope constructions and registration principles.
With the help of these he has explored the radio sources of the
universe and gradually achieved greater and greater accuracy in
the determination of direction. Definition is now so good that in
the case of visible light it corresponds to an observer on earth
being able to see the details of a postage stamp on the moon,
Ryle has developed a technique - the aperture synthesis technique
- which means that with the help of a number of small telescopes,
whose positions are mutually adjustable within a distance of
nearly 5 kilometers he can achieve a precision equalling that
obtainable by having the whole area covered by a single vast
telescope, a construction which is technically not possible. Ryle
also makes use here of the rotation of the earth to change
telescopic positions in relation to the celestial sphere.
The wealth of detail in the charting of the universe carried out
in recent years with this apparatus is absolutely unique. For a
number of years Ryle has been making observations with his
various instruments that have been of crucial significance in the
study of the physical characteristics of stars and stellar
systems and for cosmology, the study of the development of the
universe as a whole.
THE PULSARS
In the summer of 1967 Antony Hewish started a series of
observations which soon led to an extremely interesting and quite
unforeseen discovery. Some radio sources in space, later given the
name "pulsars", emitted radio signals - pulses - which were
repeated extremely regularly at intervals of a second or so. As a
result of this discovery it has been possible to establish the
presence of so-called neutron stars in the universe, something
that scientists have been speculating about ever since the
Thirties. Neutron stars are bodies which are extremely heavy, in
comparison to their size - about 10 kilometres in diameter. One
cubic centimetre of neutron-star matter of which the pulsars
consist, weighs millions of tons! The observed emission from a
pulsar shows that they must have a magnetic field which is
extraordinarily strong many millions of times stronger than any
magnetic field used in the laboratories on earth. Every signal
from the pulsars corresponds to enormous quantities of energy. It
is probable that the neutron star, which is the "nucleus" of a
pulsar, surrounds itself with a plasma, a gas conducting
electricity, and the whole system including the magnetic field
rotates. The pulsar is then perceived from the earth as a radio
beacon!
The best known pulsar is to be found in the Crab Nebula. This
nebula consists of a glowing cloud of gas, the remains of a
stellar explosion, which according to Chinese records took place
in 1054 A.D. It is one of the most interesting phenomena in the
heavens. It has been found that its centre, from which it
expands, contains a pulsar emitting not only radio pulses but
also light pulses and X-ray pulses.
The discovery of the pulsars is of paramount importance to
physics and astrophysics. The pulsars play a vital role in the
genesis of the elements and the chemical development of the
galaxies. New avenues have been opened up for studying the
properties of matter under very extreme conditions.
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