Pendulum Clocks

Modern clocks begin with Galileo's discovery of the time keeping qualities of the pendulum. Christiaan Huygens was later able harness the pendulum to the gear trains of mechanical clocks. With these 2 inventors the era of modern, accurate, mechanical clocks began.

Galileo Galilei

Galileo Galilei was born in 1564 in Pisa, near Florence in what is now modern Italy. He lived until 1642. He was a prolific inventor. Some might say he was the Elon Musk of his day.

Galileo is credited with creating modern observational astronomy, modern classical physics, the scientific method and is even credited as the inventor of the modern practice of science itself.

Galileo was living about a century after the Protestant Reformation. Luther had promoted 2 key ideas, use of the Bible alone for determining religious matters and independent study of the Bible.

The scientific method and practice of science developed by Galileo would later take hold in the Protestant areas of Northern Europe. This especially so in Protestant Germany and Protestant England. The scientific method was compatible with Protestant forms Christianity in ways that other religions did not match.

Unfortunately, Galileo lived in Catholic territory. Galileo had serious troubles with Catholic leadership. Galileo's troubles were similar to earlier troubles Luther had with Catholics. Political power does not like provable truth. Galileo spent the latter years of his life under house arrest.


As the premiere modern astronomer, Galileo had to work out the basic tooling needed for the modern practice of astronomy. Everyone practicing astronomy today is following in Galileo's footsteps. His original developments, more famously, included the optics needed to create modern telescopes.

Less well known, Galileo is responsible for the discovery of the mechanical properties of pendulums. He cared because he needed to make accurate time based measurements of objects in the night sky.


Galileo discovered a non-obvious feature of all swinging masses. The time period of those swings is based on the length of the swing. The time period is not based on the weight of the bob. The time period is not based on the angle of the swing.

The following video explains in details how this works.

Key Points

The length of a pendulum, alone, governs the time of each swing. Like many other things in the scientific world, this was counter-intuitive.

Working out how to connect pendulums to mechanical clocks would fall to Christiaan Huygens.

Christiaan Huygens

Christiaan Huygens was Dutch and lived from 1629 to 1695. He was a prolific inventor in his own right. He was the man created with working out how to connect a swinging pendulum to the gears of a mechanical clock.

The particular part that matters is called the escapement. This piece regulated the speed of the clock's gears. It also transferred a small amount of energy back into the pendulum. This kept the pendulum swinging continuously, even between winding of the clock.

The escapement is shown in the following animation. It is the blue part.

Key Points

With the invention of the pendulum, very accurate modern mechanical clocks were possible and became common by the early 1700s.