Taking the Back off the Watch: A Personal Memoir

247 Pages·2012·2.1 MB·English

by  Thomas Gold (auth.), Simon Mitton (eds.)

Taking the Back off the Watch
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# Carvel Gold
Thomas Gold
Edited by
Simon Mitton
Taking the Back
off the Watch
A Personal Memoir
Author Editor
Thomas Gold Simon Mitton
Cornell University St. Edmund’s College
Ithaca Cambridge
New York United Kingdom
United States
ISBN 978-3-642-27587-6 ISBN 978-3-642-27588-3 (eBook)
DOI 10.1007/978-3-642-27588-3
Springer Heidelberg New York Dordrecht London
Library of Congress Control Number: 2012938100
Texts by Thomas Gold # Carvel Gold
# Springer-Verlag Berlin Heidelberg 2012
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Cover image: Thomas Gold in his office at the Space Sciences Building, Cornell University, about 1970.
# Carvel Gold
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Foreword
In the year 1968, astronomers began to change the way they think about the
universe. The change was deep and fundamental. Before 1968, the universe was
seen as a peaceful assemblage of slowly evolving objects, and the job of an
astronomer was to construct an accurate picture of an almost unchanging landscape.
After 1968, the universe was seen as a drama full of violent events and cataclysms,
and the job of an astronomer was to observe and understand the processes of
change. The shift in the culture of astronomy took many years to complete, but
the year 1968 was a crucial turning point. Two people were responsible for the
sudden shift, Jocelyn Bell and Tommy Gold. Jocelyn Bell, a young radio astrono-
mer in England, discovered the rapidly pulsating radio sources that later became
known as pulsars. Tommy understood what the pulsars were and why they were
important.
I remember vividly the events of 1968. In February, we heard the news of
Jocelyn Bell’s discovery. Everyone who was interested in astronomy was trying
to understand what these mysterious radio pulses could mean. At that time, we
knew that there were two kinds of stars. There were normal stars, made of hot gas at
normal density, like our sun and all the other stars that we can see with our naked
eyes. There were white-dwarf stars, made of gravitationally collapsed matter, with
densities about a million times greater. In addition to these two well-known kinds of
stars, there was some talk of a possible third kind called neutron stars. Nobody
had ever seen a neutron star. Neutron stars were a theoretical idea originally
invented by Fritz Zwicky in 1931. Zwicky was a physicist and not an astronomer.
For that reason, few astronomers took his idea seriously. Zwicky’s idea was that
neutron stars should have densities about a million times greater than white dwarfs.
A neutron star with the mass of our sun would be only about ten kilometers in
size. Even if neutron stars existed, they would be so small that they could never be
observed, and they were therefore of no interest to traditional astronomers.
Like everyone else in 1968, I knew that normal stars sometimes pulsate, becom-
ing brighter and fainter in a regular cycle with periods of a few hours or days. These
pulsating normal stars are called Cepheid variables and are well understood. The
period of a pulsating star is roughly the time it takes for a sound wave to travel
across the star and back again. The pulsation is an unstable sound wave that
v
vi Foreword
resonates with high amplitude, like the air in a loudly played trombone. It was then
easy to calculate that a typical white dwarf, with a million times greater density and
a greater sound velocity, would have a pulsation period of the order of a second.
Jocelyn Bell’s first pulsar had a period of 1.337 s. Obviously, it was a pulsating
white dwarf. I believed that. Everyone else believed it too, except for Tommy. The
problem remained, how to understand why a pulsating white dwarf should emit
enormously powerful pulses of radio waves for our entertainment. In May 1968, the
first International Conference on Pulsars was held in New York. I was there and
heard the experts trying to explain the radio pulses. They all assumed, like me, that
the source was a pulsating white dwarf. Tommy was there too. He was not invited to
speak, since the organizers of the meeting considered his ideas to be obviously
crazy. But he spoke anyway and told us the true explanation of pulsars.
Tommy had been thinking about neutron stars long before pulsars were discov-
ered. He knew that if neutron stars were born as Zwicky had suggested, when
normal stars collapse in supernova explosions, the neutron stars are likely to be born
with extremely fast rotation and extremely strong magnetic fields. With fast rota-
tion and strong fields, the neutron star could emit radio signals like a lighthouse
with a rotating beam. The rotating radio beam would look like a pulsar. As soon as
Tommy heard of Jocelyn Bell’s discovery, he knew that this was the evidence he
had been waiting for, proving that neutron stars really exist. He told us at New York
that neutron stars should often be born spinning even more rapidly than the one that
Jocelyn Bell had found, with periods much shorter than a second. If his explanation
was right, pulsars should exist with periods measured in milliseconds. If pulsars
were white dwarfs, then periods much shorter than a second would be impossible.
In November of the same year, as a result of Tommy’s suggestion, a pulsar with
period 33 ms was discovered at the exact place in the sky where a supernova
explosion had been observed by Chinese and Korean astronomers in the year 1054.
This millisecond pulsar immediately demolished the white-dwarf theories and
proved that Tommy’s theory of pulsars was right. Neutron stars were real and
abundant in the universe. They would not only be producing radio pulses but would
have many other observable effects. They would be spewing out vast quantities of
magnetized plasma and high-energy particles into the galaxy. In one year, our
vision of the universe was transformed.
Besides explaining pulsars and proving that neutron stars exist, Tommy left his
imprint on the world of astronomy in other ways. In 1960, he moved from Harvard
to Cornell University, where he became chairman of the astronomy department
with authority to expand the department and to create a brand-new “Center for
Radiophysics and Space Research.” Under his management, the Center for Radio-
physics became a world-class institution for people doing nontraditional kinds of
astronomy. One of the luminaries whom Tommy attracted to the center was Carl
Sagan. Sagan became firmly attached to Cornell and stayed there for the rest of his
life. Sagan was like Tommy, interested in everything and always ready to plunge
into new ventures. The two of them were a good team, Sagan as the spellbinding
television personality who made things in the sky exciting to the public, Tommy as
the organizer who made things happen on the ground.
Foreword vii
One of the things that Tommy made happen was the conversion of the Arecibo
Radio Telescope into a superb instrument for radio astronomy. The Arecibo
telescope had been built by the US Department of Defense as an instrument for
studying the ionosphere. The ionosphere is important for military communications
and is subject to rapid fluctuations. The telescope was designed as a powerful radar
giving prompt information about the current state of the ionosphere. By good luck,
Cornell University was responsible for running the telescope. When the telescope
was built in 1963, Tommy was in charge of its nonmilitary operations. He quickly
found out that the telescope worked very well for the ionospheric observations for
which it was designed but worked very poorly for radio astronomical observations
which require high sensitivity. Without high sensitivity, the telescope could not
take advantage of its huge size to see faint radio sources at the edge of the universe.
It turned out that the correction of this design flaw required a complete replacement
of large parts of the instrument. The replacement was costly in time and money.
Tommy had to fight hard to get it done. It took nine years before it was finished.
Without his stubborn determination, it would probably not have happened. In the
end, after the nine years were over, the Arecibo telescope became what Tommy had
intended it to be, the finest instrument in the world for studying faint point sources
such as pulsars.
Tommy loved Arecibo and was intensely proud of what he had done there. On
one stormy day in Puerto Rico, he was acting as tour guide to a visiting committee
of scientists who came to Arecibo to see the telescope in operation. He led us along
a high catwalk, starting on one of the mountains from which the antenna is
suspended and ending at the platform of the antenna. We emerged on the platform,
a huge steel structure, suspended 500 ft above the reflecting dish on the ground
below us. The platform was steady as a rock, with no perceptible motion, although
the wind was whistling in our ears and lightning flashes were visible from an
approaching storm. Tommy walked ahead of us to the edge of the platform,
which was unprotected by any kind of railing. He chose this moment to give us
a lecture, describing the history of the telescope and the plans for its future. He
talked with great animation for 20 min, facing us with his heels on the edge of the
platform, with nothing behind him but a 500-foot drop into thin air. We were
huddled together in front of him, nervously waiting for the gust of wind that
would blow him into oblivion, trying to listen to what he was saying. At the end
of 20 min, he calmly asked for questions and was in no hurry to move away from the
edge. That was Tommy, a great circus performer as well as a great scientist, proud
of his physical mastery as well as of his intellectual achievements. The Arecibo
telescope remained at the forefront of radio astronomy for 40 years and is only now
beginning to become obsolete. It is not only a wonderful scientific tool but also
a wonderful piece of architecture, perhaps the most beautiful man-made object of
the modern era. It is a fitting monument to the life and work of Tommy Gold.
In the last years of his life, Tommy’s main interest was the origin of hydro-
carbons on the Earth. The hydrocarbons are natural gas and oil, which also happen
to be of immense importance to the economic activities of humans and to the
ecology of the planet. The prevailing view of experts in Western countries is that
viii Foreword
hydrocarbons are by-products of biology, resulting from the decomposition of
bodies of ancient plants and microbes that died and were buried for millions of
years. Tommy, together with many of the petroleum experts in Russia, took the
opposite view, believing that the hydrocarbons came up from nonbiological sources
deep in the Earth and only became contaminated with biological molecules because
microbes invaded and fed on them on their way up. It was natural for an astronomer
to prefer a nonbiological origin of hydrocarbons, since hydrocarbons are abundant
in the outer planets of the solar system and were probably abundant in the material
out of which the Earth condensed. Tommy’s views are still fiercely opposed by
a majority of experts. The debate rages on. I have to confess that I am like Tommy,
more familiar with astronomy than with petroleum chemistry, and I believe that the
experts are wrong.
Tommy was tough and never gave up a fight. He liked to tell us how he learned
to be tough, as a Jewish kid fighting gangs of Nazi hoodlums in the streets of Berlin
in the years 1930–1933 when Hitler was rising to power. He was a street kid from
age 10 to age 13. The hoodlums knew that he was Jewish. They were mostly much
bigger and older, but he was quicker and smarter. He learned to hit them hard and
never show fear. Those years in Berlin shaped his character for the rest of his life.
As a final glimpse of Tommy, I like to recall a morning in the Swiss ski resort of
Arosa in the spring of 1947. There is an almost vertical mountainside overlooking
Arosa. It was then deeply covered with fresh snow. It had one or two steeply
winding trails, for expert skiers only. That morning, the whole town was astonished
to see four parallel pairs of ski tracks coming straight down the mountain from top
to bottom, avoiding the trails and jumping over minor obstacles such as rocks and
cliffs. Everyone was wondering who the four mysterious strangers could be. The
four strangers had evidently come down the mountain together at high speed like
dive bombers. Only a few of us who knew Tommy could guess what had happened.
Tommy had gone out by himself before breakfast and skied down the mountain
alone four times, each time keeping at a fixed distance from his previous track. That
was his way of showing the world what he could do.
NJ, USA Freeman Dyson
Introduction
Thomas Gold (1920–2004) was one of the most remarkable astronomers in the
second half of the twentieth century. In a career that spanned half a century, he
worked in astrophysics, cosmology, physiology, radio astronomy, geophysics, and
lunar science, where he was by turns an innovative practitioner and a daring
theorist. After completing his war service in naval intelligence, he held positions
at the University of Cambridge, the Royal Greenwich Observatory, Harvard Uni-
versity, and finally Cornell University in 1959.
Gold was born in Vienna on May 22, 1920, where his father was a wealthy
industrialist with the means to provide a comfortable and privileged life for his son
and heir. However, the economic crisis of the late 1920s meant the family moved to
Berlin where his father became a metals trader. Gold’s father, Max, was of Jewish
origin from the Polish Ukraine and his mother was of German Catholic origin.
Neither parent had the slightest interest in religion. They fled Germany in 1933 and
settled in England in 1937. His father’s gift of a watch, which Gold took apart and
reassembled, led to his interest in technology, and Thomas entered Trinity College,
Cambridge, in October 1939 to read engineering.
In May 1940, the British Government introduced the internment of all men of
German or Austrian descent who were resident in eastern England. Behind the
barbed wire, Tommy encountered Hermann Bondi, who had fled from Vienna, and
this was the start of a lifelong friendship. The internees were transferred to Canada,
and then brought back to England in 1941. Gold completed his engineering degree,
getting a miserable result, an ordinary degree, in 1942. Given the scale of what he
later achieved, the poor result can be put down to the fact that almost all of the
teaching faculty at Cambridge were engaged elsewhere on the war effort, with
instruction left in the hands of elderly dons.
Those who were away on war work included the Cambridge theoretical physicist
Fred Hoyle who was at a secret experimental naval radar station from May 1940. By
1942, Hoyle was in charge of the theory group at the Admiralty Signals Establish-
ment, where Bondi and Gold joined him. Thus was the stage set for a dazzling
collaboration of cosmologists. The trio had many discussions about an unsolved
problem in cosmology that had surfaced in the 1930s: the age of the Earth appeared
to be twice the age of the universe. Gold was the first to propose, in late 1947,
ix
x Introduction
what came to be known as the steady-state theory of cosmology. Hoyle and Bondi,
who were more accomplished applied mathematicians than Gold, worked through
the implications of Gold’s natural philosophy that the universe preserves its
appearances throughout time, existing in a stable state of expansion with continuous
creation of new matter. In 1948, Gold and Bondi published a paper on the philo-
sophical aspects of the new theory for the origin of the universe, while Hoyle
published his theory of a creation field to account for the new matter compensated
for the effects of expansion. In the eyes of the general public, the theory received
a massive boost as a result of Hoyle’s BBC radio broadcasts in 1949 and 1950, in
the first of which he proposed the name “big bang” to describe the rival theory. The
discovery of the cosmic microwave background in 1963 led to general acceptance
of the big bang theory, although Gold never lost faith in steady-state cosmology.
In 1949, Gold was appointed to a junior faculty position in the Cavendish
Laboratory (Department of Physics) at Cambridge. This brought him into daily
contact with Martin Ryle in the radio group at the laboratory. In those days, Ryle’s
group were doing fundamental development work on instrumentation for investi-
gating cosmic radio sources, of which some 50 were known. Gold was sucked into
furious arguments between Ryle and Hoyle, who were both slightly older than him.
Ryle felt that the cosmic sources were stars in our galaxy, whereas Hoyle and Gold
believed them to be extragalactic. Gold unwisely engaged in loud criticism of Ryle
and that led to his modest appointment not being renewed.
His luck changed remarkably when the astronomer royal offered him the post of
chief assistant (a senior position despite its title) at the Royal Greenwich Observa-
tory. Gold was given a free hand, and he decided his future was in space research.
He took the first steps in areas that would become mainstream in his professional
career: the nature of the lunar surface and the role of magnetic fields in space. The
Oxford English Dictionary gives him credit for coining the noun magnetosphere:
1959 T. Gold in Jrnl. Geophysical Res. 64 1219/1 The region above the ionosphere in which
the magnetic field of the earth has a dominant control over the motions of gas and fast
charged particles . . . is known to extend out to a distance of the order of 10 earth radii; it
may appropriately be called the magnetosphere.
He had to resign abruptly from the Royal Observatory in 1956 because he was
unable to work with the newly appointed astronomer royal, Richard Woolley. That
is becauseWoolley was implacably opposed to space research and radio astronomy,
the very fields in which Gold would excel. He and his family left England for good,
accepting a chair in radio astronomy at Harvard in 1957. Two years later, Cornell
University offered him the headship of its department of astronomy, and Gold made
his final move.
At Cornell, he founded and directed the Center for Radio Physics and Space
Research. Then he persuaded the US Defense Department to fund the construction
of the giant radio telescope at Arecibo in Puerto Rico. Commissioning the telescope
proved to be immensely challenging, but Gold overcame shortcomings of the
design and went on to make great discoveries. This period of Gold’s career is
recounted in Chap. 7.