The most beautiful experiments – Galilieo

Galileo Galilei

Can an experiment really be described as beautiful? I guess that really depends upon the beholder, but I think it can, and I hope to convince you of that in a new series of posts, detailing  some of the most well executed and sublimely illuminating experiments in scientific history.

To begin with at least, these will be quite antiquated tales. Gone are the days when a gentleman of science could simply get out a handy prism in his study and start refracting light and speculating about the nature of reality. These days it takes DNA sequencing machines and armies of  bespectacled geeks to find out the smallest new detail about our Universe. I suppose one could argue that the discoveries of today are much more relevant and exciting than, those of yesteryear but they are also much harder to understand – and as such harder to write about with some degree of lucidity. What is more, I am often surprised at how little I know about how we actually found out the scientific facts we take for granted in everyday life. And I think this is true of many of us (1).

How about this for example? A 10 Kg metal bar and a 1 Kg metal bar fall to earth at the same speed, despite their difference in mass. But I can’t even really remember why that is if I’m honest, let alone try to explain it from first principles. That’s why I have such a huge amount of respect for people like Galileo Galilei, who worked out the rules of acceleration even before such a thing as a stopwatch existed.

 ‘It is very unpleasant and annoying to see men , who claim to be peers of anyone in a certain field of study, take for granted certain conclusions which later are quickly and easily shown by another to be false.’

– Salviati, in Galileo’s, The Two New Sciences (2) 

At the time of Galileo’s early career – around the year 1600 – the fact about metal bars of different masses falling at the same speed had already been observed. What no one knew however, was what happened in terms of their acceleration. Clearly, when the bar was released it had no speed and when it hit the floor it had ‘some’ speed. But did it accelerate gradually? Did it perhaps accelerate most quickly at the beginning of it’s fall when it had the most potential energy? No one knew.

Random fact of the day; Galileo’s finger is on display in the Museo di Storia della Scienza in Florence, Italy. Apparently this really is his finger. It was removed and put on display when his body was exhumed to be moved to a better burial site around 1742.

What Galileo did to try and answer this tricky problem was construct a smooth wooden rail down which he spent his days rolling smooth bronze balls. The ramp was about 20 feet long, which gave him just about adequate time to mark the position of the ball as it rolled down the track at regular intervals of time.

But there has been much debate about Galileo’s experiment, and whether he really did it. In his writings he describes measuring the time taken for the ball to roll down the slope with a water-clock. But if we think about it, this begins to seem a bit crazy. The necessary way to do the experiment would be to mark out a series of equally spaced points on the track, and observe the exact point of time when the ball rolled past it. At that instant, the water-clock would have to be consulted, the amount of water weighed and the calculations worked out. Isn’t all that quite a big ask?

Some, like historian of science Stillman Drake, have postulated that Galileo lied about how he really did his experiment. Why would he do that? Well, to answer that question, a graduate student named Thomas Settle (3) set out to repeat the famous experiment and try and work out logically what the easiest way to do it would be, using simple materials.

 Settle found that the answer was singing. Taking the opposite approach to trying to measure the time for the ball to go a specific distance, Settle found it much easier to let the ball roll and mark it’s position with some chalk on the 4th beat of a song. Apparently he favoured that old favourite ‘onward christian soldiers’. It’s suprising how accurately we can keep time in our heads. Even so, Settle then improved his method by fixing strings of cat-gut across the path of the ball, so that it lightly ‘strummed’ them as it rolled past. He could then roll the ball lots of times, adjusting the position of the cat gut string each time until the ‘strumming’ exactly matched his singing.

So why might Galileo have lied? Maybe it was just to save face; frankly, it would have sounded just as silly 400 years ago as it does today to claim you’ve solved an intellectual problem by rolling balls down a track and timing them by singing!

Galileo was not only smart enough to devise a devilishly clever experiment, but he did it with such skill that even using his crude method, his numbers were accurate enough for him to work out the pattern in his results and predict that the distance travelled by a falling object is directly related to the square of the time taken. It’s still the law we use today. What a beautiful experiment.


1. I should also mention that the inspiration for this post came largely from George Johnson’s interesting book, The ten most beautiful experiments.

2. Galileo wrote up his musings on the nature of motion in this book. It makes an interesting alternative to todays peer-reviewed journals. It’s written in the form of a discourse between three men, two of whom are not very clever and a third ‘Salviati’ who represents Galileo. Salviati spends most of the book telling the other two guys all about the experiments he’s done and why they’re so great.

3. Check out an excerpt from Settle’s book on the subject.

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5 Responses to The most beautiful experiments – Galilieo

  1. bethanlowder says:

    That’s the best idea ever (writing a book where a clever person explains things to not such clever people)! Do you think my examiners would just love it if I wrote my thesis like that?

  2. Joe Fisk says:

    Many, many thanks for that Josh. I quite agree, most beautiful indeed. Did you know (I’m sure you did!) that when people are trained to give CPR they are told to sing a song in their heads while doing the chest compressions? Apparently, the best speed is 100bpm, so “Nelly the Elephant” and “Match of the Day” are among the suggested songs…

  3. tom says:

    I would like to see more posts on physics experiments….

  4. Audrey says:

    Being out of work, I actually have time to read all ths. Very beautiful ideas. The only thing is it’s should be its in this context. “It’s” means “it is”. Sorry but I am a compulsive proof reader. love Audrey x

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