o_1977r8vv9vk1ts2ms0kd8pksa.pdf

a Chapter 1 Doppler Sonography: A Brief History 3
earth causing apparent spectral shifts of the emitted
white light. The spectrum would shift toward blue if
the star approached the earth; conversely, the spectrum
would shift to red if the star receded away from the
earth. When describing these phenomena Doppler
did not take into account preexisting research on light
transmission and spectrum. Herschel [3] had already
discovered infrared radiation, and Ritter [4] had described
ultraviolet radiation; but it appears that Doppler
was unaware of these important developments.
Verification of Doppler's Theory
Fig. 1.3. C. H. D. Buys Ballot (1817±1890). (From [40], with
permission)
As was to be expected, the paper generated critical
responses. The most significant challenge came from
a young Dutch scientist working at the University of
Utrecht in Holland, Christoph Hendrik Diederik Buys
Ballot (Fig. 1.3). In 1844 Buys Ballot proposed to refute
the Doppler theory by designing an experiment
involving sound transmission as his doctoral research
project. Conveniently for him, a new railroad had just
been established between Amsterdam and Utrecht,
and the Dutch government gave him permission to
use this railway system to verify the Doppler effect
on sound transmission (Fig. 1.4). The first experiment
was designed in February 1845. Two horn
players who apparently had perfect pitch were chosen
to participate in the experiment. The calibration was
accomplished by one musician blowing a note and
the other identifying the pitch of the tone. After this
calibration was performed, one player was positioned
on the train, and the other stood along the track. As
the train passed, the stationary musician on the
trackside perceived that the note blown by the musician
on the train was half a note higher when the
train approached him and half a note lower when it
moved away. Unfortunately, a raging blizzard forced
Buys Ballot to abandon his experiment and to reschedule
it in a more temperate season. The results from
the first experiment were published within less than a
month in a music journal [5].
Buys Ballot conducted the experiment again in
early June of the same year [6]. Three teams were stationed
along the track. Each team was composed of a
horn player, an observer, and a manager. A fourth
team was on a flat car behind the locomotive. Buys
Ballot positioned himself on the foot plate next to the
engineer. This experiment was more sophisticated,
but it also encountered environmental complications
as the summer heat seriously interfered with the correct
tuning of the musical instruments. The musicians
originally tried to use one-sixteenth of a single
note but failed, and the final experiment was done in
eights. The results were remarkable despite all the
trials and tribulations. The study that set out to refute
the Doppler theory ultimately confirmed it. Buys
Ballot proved not only the existence of the Doppler
effect in relation to sound transmission but its angle
dependency as well. Incredibly, Buys Ballot still refused
to accept the validity of the theory for the propagation
of light and most of the scientific community
of the nineteenth century did not acknowledge
the validity of Doppler's theory because of his erroneous
interpretation of astronomical phenomena.
As translated by Eden [1], Doppler's response was
impressive in its foresight: ªI still hold the trust ± indeed,
stronger than ever before ± that in the course
of time, this theory will serve astronomers as a welcome
help to probe the happenings of the universe, at
times when they feel deserted by all other methodsº
[7]. This statement was prophetic. Since the beginning
of the twentieth century, the Doppler principle
has been used extensively not only in astronomy but
also in the immensely diverse fields of science and
technology.
Doppler lived only 10 years after publishing his
paper on the frequency shift; however, these few years
brought him well-deserved recognition and honor. He