Page 36 - Singiresu S. Rao-Mechanical Vibrations in SI Units, Global Edition-Pearson (2017)

1.2 brieF history oF the study oF Vibration 33

FiGure 1.3 Schematic diagram of the world’s first seismo-
graph, invented in China in a.d. 132.

1.2.2 Galileo Galilei (1564–1642) is considered to be the founder of modern experimental sci-
From Galileo to ence. In fact, the seventeenth century is often considered the “century of genius” since the
rayleigh foundations of modern philosophy and science were laid during that period. Galileo was
inspired to study the behavior of a simple pendulum by observing the pendulum move-
ments of a lamp in a church in Pisa. One day, while feeling bored during a sermon, Galileo
was staring at the ceiling of the church. A swinging lamp caught his attention. He started
measuring the period of the pendulum movements of the lamp with his pulse and found
to his amazement that the time period was independent of the amplitude of swings. This
led him to conduct more experiments on the simple pendulum. In Discourses Concerning
Two New Sciences, published in 1638, Galileo discussed vibrating bodies. He described the
dependence of the frequency of vibration on the length of a simple pendulum, along with
the phenomenon of sympathetic vibrations (resonance). Galileo’s writings also indicate
that he had a clear understanding of the relationship between the frequency, length, ten-
sion, and density of a vibrating stretched string [1.5]. However, the first correct published
account of the vibration of strings was given by the French mathematician and theolo-
gian, Marin Mersenne (1588–1648), in his book Harmonicorum Liber, published in 1636.
Mersenne also measured, for the first time, the frequency of vibration of a long string and
from that predicted the frequency of a shorter string having the same density and tension.
Mersenne is considered by many the father of acoustics. He is often credited with the dis-
covery of the laws of vibrating strings because he published the results in 1636, two years
before Galileo. However, the credit belongs to Galileo, since the laws were written many
years earlier, but their publication was prohibited by the orders of the Inquisitor of Rome
until 1638.
Inspired by the work of Galileo, the Academia del Cimento was founded in Florence in
1657; this was followed by the formations of the Royal Society of London in 1662 and the
Paris Academie des Sciences in 1666. Later, Robert Hooke (1635–1703) also conducted