Galileo Galilei’s Swinging Chandelier

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When I was an unpublished but eager new writer, I found a subject that eventually evolved into a series of books for young people.  As a science teacher, I knew the classic stories of discoveries made by Archimedes, Fleming, Pythagoras and a few other legendary mathematicians and scientists, but I didn’t realize how extensive the story pool was until I stumbled upon a weathered library book titled ‘Stories from Science‘. 

The book fascinated me. Until then, I’d thought of writing fiction, but the subjects in the book captivated me. I abandoned my fiction ambitions (for the moment, anyway) and wrote short stories about these instead. One book, Accidental Discoveries: From Laughing Gas to Dynamite, led to three others: Mysteries of TimeWhose Bright Idea Was It? True Stories of Inventions & Extreme Science: Science in the Danger Zone.

In the end, opting to write non-fiction narratives was a wise choice. So too was writing about science, a subject familiar and fascinating to me. Without realizing it, I was learning how to write stories of all kinds, a handy thing when I ventured into true adventure and later novels. I became ‘that guy’ – the guy who wrote science and history for kids. Not a bad moniker for a start-up writer, and perhaps there’s something of a lesson or two in my story for others interesting in writing. My advice?  Write about subjects that fascinate you. Tap into your sphere of expertise, knowledge or experience. Establish a line of credibility.  Write. Write. Write.  

The story of Galileo’s swing chandelier was one of the first I wrote. A brief mention of Galileo’s discovery in ‘Stories from Science‘ sparked my interest.  Additional research brought home the details. Eventually, several drafts later, the story became my own. And now it is yours, too.


Rather than listen to a Sunday service in 1581, seventeen-year-old Galileo Galilei studied a chandelier hanging overhead in the huge cathedral at Pisa, Italy.

Air currents flowing through the lofty building moved the chandelier from side to side, back and forth. Sometimes the chandelier moved gently; sometimes it swung in a wide arc. No matter what the size of its swing, it seemed to Galileo that the chandelier kept steady time.

One, two, three beats

There were no clocks or watches in those days. To time the chandelier’s swings, Galileo felt for the pulse in his wrist. He counted the pulse beats. One, two, three beats for one swing. One, two, three beats for another. No matter how wide or narrow the swing, it always took the same number of pulse beats.

Right after the service, Galileo raced home. He suspended a weight from a long string to create a pendulum then he pulled the weight back a short distance, released it, and timed its swing.  He tried it again, this time pulling the weight back farther before releasing it. After many tries, Galileo confirmed his suspicions – the time it took to make one swing was always the same whether the swing was wide or narrow.

Galileo tried other experiments with his pendulum. He discovered that the length of string, amount of weight, and other factors all had some predictable relationship to the time of a pendulum’s swing.

Galileo’s timepiece

galileos-boardSome years later, Galileo extended his research with gravity. Did all objects fall at the same rate?  To find out, he adapted the pendulum as a timepiece. First he carved a long, straight groove down the center of a board. When he raised the board slightly at one end and released a ball, it slowly rolled down the groove.

Galileo marked off his grooved board into small divisions of equal length. For a timing device, he rigged up a water-filled container with a small hole in the bottom. By counting water drops, he could keep track of time.

He released one ball at a time from the higher end of the board. As the balls rolled, Galileo timed how long it took them to cross each division of the board. To his surprise, Galileo discovered that the balls didn’t travel down the track at an even rate. Instead, they accelerated – or sped up – as they got farther down the groove. Falling objects, he found, picked up speed as they fell to the earth.

Galileo’s gift to science

In many ways, the swinging chandelier started a revolution in the world of science. With his pendulum investigations, Galileo pioneered the scientific method –the system of carefully controlled experiments and observations that modern scientists use today to prove a natural law beyond a shadow of a doubt

A more detailed version of this story can be found in Accidental Discoveries: From Laughing Gas to Dynamite

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