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FOREWARD BY FREEMAN J. DYSON
to "The Deep Hot Biosphere" by Thomas
Gold
The first time I met Tommy Gold was in 1946,
when I served as a guinea-pig in an experiment that
he was doing on the capabilities of the human ear.
Humans have a remarkable ability to discriminate
the pitch of musical sounds. We can easily tell
the difference when the frequency of a pure tone
wobbles by as little as one percent. How do we do
it? This was the question that Gold was determined
to answer. There were two possible answers. Either
the inner ear contains a set of finely-tuned
resonators that vibrate in response to incident
sounds. Or the ear does not resonate but merely
translates the incident sounds directly into neural
signals which are then analyzed into pure tones by
some unknown neural process inside our brains. In
1946 the professional physiologists who were
experts in the anatomy and physiology of the ear
believed that the second answer must be correct,
that the discrimination of pitch happens in our
brains and not in our ears. They rejected the
first answer because they knew that the inner ear
is a small cavity filled with flabby flesh and
water. They could not imagine the flabby little
membranes in the ear resonating like the strings of
a harp or a piano.
Gold designed his experiment to prove the
experts wrong. The experiment was simple, elegant
and original. During World War Two he had been
working for the Royal Navy on radio-communications
and radar. He built his apparatus out of
war-surplus Navy electronics and headphones. He
fed into the headphones a signal consisting of
short pulses of a pure tone, separated by intervals
of silence. The silent intervals were at least ten
times as long as the period of the pure tone. The
pulses were all the same shape, but they had phases
which could be reversed independently. To reverse
the phase of a pulse means to reverse the movement
of the speaker in the headphone. The speaker in a
reversed pulse is pushing the air outward when the
speaker in an unreversed pulse is pulling the air
inward. Sometimes Gold gave all the pulses the
same phase, and sometimes he alternated the phases
so that the even pulses had one phase and the odd
pulses had the opposite phase. All I had to do was
to sit with the headphones on my ears and listen
while Gold put in signals with either constant or
alternating phases. I had to tell him from the
sound whether the phase was constant or
alternating.
When the silent interval between pulses was ten
times the period of the pure tone, it was easy to
tell the difference. I heard a noise like a
mosquito, a hum and a buzz sounding together, and
the quality of the hum changed noticeably when the
phases were changed from constant to alternating.
We repeated the trials with longer silent
intervals. I could still detect the difference,
when the silent interval was as long as thirty
periods. I was not the only guinea-pig. Several
other friends of Gold listened to the signals and
found similar results. The experiment showed that
the human ear can remember the phase of a signal,
after the signal stops, for thirty times the period
of the signal. To be able to remember phase, the
ear must contain fine-tuned resonators that
continue to vibrate during the intervals of
silence. The result of the experiment proved that
pitch-discrimination is mainly done in the ear and
not in the brain.
Besides having experimental proof that the ear
can resonate, Gold also had a theory to explain how
a fine-tuned resonator can be built out of flabby
and dissipative materials. His theory was that the
inner ear contains an electrical feed-back system.
The mechanical resonators are coupled to
electrically powered sensors and drivers, so that
the combined electromechanical system works like a
finely-tuned amplifier. The positive feed-back
provided by the electrical components counteracts
the damping produced by the flabbiness of the
mechanical components. Gold's experience as an
electrical engineer made this theory seem plausible
to him, although he could not identify the
anatomical structures in the ear that functioned as
sensors and drivers. In 1948 he published two
papers, one reporting the results of the experiment
and the other describing the theory.
Having myself participated in the experiment and
listened to Gold explaining the theory, I never had
any doubt that he was right. The professional
auditory physiologists were equally sure that he
was wrong. They found the theory implausible and
the experiment unconvincing. They regarded Gold as
an ignorant outsider intruding into a field where
he had no training and no credentials. So for
thirty years his work on hearing was ignored, and
he moved on to other things.
Thirty years later, a new generation of auditory
physiologists began to explore the ear with far
more sophisticated tools. They discovered that
everything that Gold had said in 1948 was true.
The electrical sensors and drivers in the inner ear
are now identified. They are two different kinds
of hair-cells, and they function in the way Gold
said they should. The community of physiologists
finally recognized the importance of his work,
forty years after it was published.
Gold's study of the mechanism of hearing is
typical of the way he has worked throughout his
life. About once every five years, he invades a
new field of research and proposes an outrageous
theory that arouses intense opposition from the
professional experts in the field. He then works
very hard to prove the experts wrong. He does not
always succeed. Sometimes it turns out that the
experts are right and he is wrong. He is not
afraid of being wrong. He was famously wrong at
least twice, once when he promoted the theory of a
steady-state universe in which matter is
continuously created to keep the density constant
as the universe expands, and once when he predicted
that the moon would be covered with
electrostatically supported dust into which the
astronauts would sink as soon as they stepped onto
the surface. When he is proved wrong, he concedes
defeat with good humor. Science is no fun, he
says, if you are never wrong. His wrong ideas are
insignificant compared with his far more important
right ideas. One of his important right ideas was
the theory that pulsars, the regularly pulsing
celestial radio-sources discovered by
radio-astronomers in 1967, are rotating neutron
stars. Unlike most of his right ideas, his theory
of pulsars was accepted almost immediately by the
experts.
Another of Gold's right ideas was rejected by
the experts for an even longer time than his theory
of hearing. This was his theory of the
ninety-degree flip of the axis of rotation of the
earth. In 1955 he published a revolutionary paper
with the title ``Instability of the Earth's Axis of
Rotation''. He proposed that the earth's axis
might occasionally flip over through an angle of
ninety degrees within a time of the order of a
million years, so that the old north and south
poles would move to the equator, and two points of
the old equator would move to the poles. The flip
would be triggered by movements of mass that would
cause the old rotation axis to become unstable and
the new rotation axis to become stable. For
example, a large accumulation of ice at the old
north and south poles might cause such an exchange
of stability. Gold's paper was ignored by the
experts for forty years. The experts at that time
were focusing their attention narrowly on the
phenomena of continental drift and the theory of
plate tectonics. Gold's theory had nothing to do
with continental drift or with plate tectonics, and
it was therefore of no interest to them. The flip
predicted by Gold would occur much more rapidly
than continental drift, and would not change the
positions of continents relative to one another.
The flip would only change the positions of
continents relative to the rotation axis.
In 1997 Joseph Kirschvink, an expert on rock
magnetism at the California Institute of
Technology, published a paper presenting evidence
that a ninety-degree flip of the rotation axis
actually occurred during a geologically short time
in the early Cambrian era. This discovery is of
great importance for the history of life, since the
time of the flip appears to coincide with the time
of the ``Cambrian Explosion'', the brief period
when all the major varieties of higher organisms
suddenly appear in the fossil record. It is
possible that the flip of the rotation axis caused
profound environmental changes in the oceans and
triggered the rapid evolution of new life-forms.
Kirschvink gives Gold credit for suggesting the
theory that makes sense of his observations. If
the theory had not been ignored for forty years,
the evidence that confirms it might have been
collected sooner.
Gold's most controversial idea is the
non-biological origin of natural gas and oil. He
advocates a theory that natural gas and oil come
from reservoirs deep in the earth and are relics of
the material out of which the earth condensed. The
biological molecules found in oil show that the oil
is contaminated by living creatures, not that the
oil was produced by living creatures. This theory,
like his theories of hearing and of polar flip,
contradicts the entrenched dogma of the experts.
Once again, Gold is regarded as an intruder
ignorant of the field that he is invading. In
fact, Gold is an intruder but he is not ignorant.
He knows the details of the geology and chemistry
of natural gas and oil. His arguments supporting
his theory are based on a wealth of factual
information. Perhaps it will once again take us
forty years to decide whether the theory is right.
Whether the theory of non-biological origin is
ultimately found to be right or wrong, the
collection of evidence to test it will add greatly
to our knowledge of the earth and its history.
Finally, the most recent of Gold's revolutionary
proposals, the theory of the deep hot biosphere, is
the subject of this book. The theory says that the
entire crust of the earth, down to a depth of
several miles, is populated with living creatures.
The creatures that we see living on the surface are
only a small part of the biosphere. The greater and
more ancient part of the biosphere is deep and hot.
The theory is supported by a considerable mass of
evidence. I do not need to summarize the evidence
here, because it is clearly presented in this book.
I prefer to let Gold speak for himself. The
purpose of my foreword is only to explain how the
theory of the deep hot biosphere fits into the
general pattern of Gold's life and work. Gold's
theories are always original, always important,
usually controversial and usually right. It is my
belief, based on fifty years of observation of Gold
as a friend and colleague, that the deep hot
biosphere is all of the above: original, important,
controversial and right.
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