Universe Today
Hydrostatic Balance:
Inspired by the story of Archimedes' and his "Eureka" moment, Galileo began looking into how jewelers weighed precious metals in air, and then by displacement, to determine their specific gravity. In 1586, at the age of 22, he theorized of a better method, which he described in a treatise entitled La Bilancetta (or "The Little Balance").
In this tract, he described an accurate balance for weighing things in air and water, in which the part of the arm on which the counter weight was hung was wrapped with metal wire. The amount by which the counterweight had to be moved when weighing in water could then be determined very accurately by counting the number of turns of the wire. In so doing, the proportion of metals like gold to silver in the object could be read off directly.
Galileo's Pump:
Pendulum Clock:
During the 16th century, Aristotelian physics was still the predominant way of explaining the behavior of bodies near the Earth. For example, it was believed that heavy bodies sought their natural place or rest - i.e at the center of things. As a result, no means existed to explain the behavior of pendulums, where a heavy body suspended from a rope would swing back and forth and not seek rest in the middle.
Already, Galileo had conducted experiments that demonstrated that heavier bodies did not fall faster than lighter ones - another belief consistent with Aristotelian theory. In addition, he also demonstrated that objects thrown into the air travel in parabolic arcs. Based on this and his fascination with the back and forth motion of a suspended weight, he began to research pendulums in 1588.
In 1602, he explained his observations in a letter to a friend, in which he described the principle of isochronism. According to Galileo, this principle asserted that the time it takes for the pendulum to swing is not linked to the arc of the pendulum, but rather the pendulum's length. Comparing two pendulum's of similar length, Galileo demonstrated that they would swing at the same speed, despite being pulled at different lengths.
According to Vincenzo Vivian, one of Galileo's contemporaries, it was in 1641 while under house arrest that Galileo created a design for a pendulum clock. Unfortunately, being blind at the time, he was unable to complete it before his death in 1642. As a result, Christiaan Huygens' publication of Horologrium Oscillatorium in 1657 is recognized as the first recorded proposal for a pendulum clock.
