Crosstalk: When an Apple Fell on Newton’s Head, and Stories on the Process of Discovery

A discovery is made only when the appropriate tools required for that discovery are invented – and almost never completely by chance.

Louis Pasteur performing an experiment in his lab. Credit: Wikimedia Commons

Louis Pasteur performing an experiment in his lab. Credit: Wikimedia Commons

This is the second part of an essay on the process of scientific discovery. The first part is here.

Research is to see what everybody else has seen, and to think what nobody else has thought.

–Albert Szent-Gyorgyi

There is a famous story from ancient Syracuse, about the king Hiero and the local genius Archimedes. As the fable goes, Hiero was convinced that the goldsmith making his crown had cheated him. He tasked Archimedes to ensure that the crown was of pure, undiluted gold. Archimedes panicked when set this task and decided to take a bath to calm down. You know the rest. He sat in the tub, observed the displaced water as he entered the tub, and realised that the amount of water displaced was his own volume. He therefore raced out of the bath to the palace stark naked, shouting “Eureka!”, having just discovered the principle of buoyancy (or the Archimedes principle).

This makes good reading. Unfortunately, it is mostly untrue. There usually aren’t these kinds of eureka moments in science or discovery.

Most important discoveries are made through an accumulation of knowledge, which advances a field sufficiently so as to enable the discovery. Specific individuals are credited with a discovery, but their work comes not in eureka moments, but relies on their being able to connect dots, using findings made by multiple individuals. Indeed, the world of scientific (and all) discovery follows certain patterns, with two important components.

Relentless pursuit

Sometimes, the questions are obvious but the phenomenon unexplained. At some point in time, people asked: why is the sky blue? What keeps things on the ground and not fly away? Why are there tides in the oceans? The discovery lies in understanding and providing an explanation for these phenomena. Of course, we have Newton to thank for understanding blue skies or gravity. The popular story of gravity has Newton whiling away a lazy afternoon under an apple tree, half asleep, when an apple falls on his head, wakes him up, and eureka! he cracks the mystery of gravity. Yet that story is far from the truth. Newton was in a part of the world and at a time when these questions were under intense investigation. Many rules of planetary motion and heavenly bodies were being postulated, while there was an explosion in the studies of mathematics.

Much of the primary rules of calculus came from the work of ancient and medieval mathematicians in Greece, Persia and India, and this had been consolidated. Both Leibnitz and Newton were primed to complete the rules of calculus. Indeed, Newton had the shoulders of giants to stand on, and used his years of intense study and relentless pursuit of multiple disciplines (primarily mathematics, and the observation of heavenly bodies) to nail the theory of gravity. The apple probably provided a nice snack along the way.

Another story of relentless pursuit is the story of vaccination and Louis Pasteur. As we’ll see later, Pasteur and others worked meticulously for years to show that microbes (and not bad air, or spirits) caused diseases. They postulated that weakened (or attenuated) microbes could be used to prevent a disease, and famously used weakened anthrax to successfully immunise people from the disease. Of course, like most stories, there is a darker side to this.

Pasteur claimed all credit for vaccination, yet the first proven vaccinations were done by another, now forgotten, Frenchman named Jean-Joseph Henri Toussaint. Toussaint was a vet who greatly admired Pasteur, read all his work, studied cholera and anthrax, and came up with a method to weaken anthrax (with potassium dichromate), and then use it to immunise sheep. Sadly, Pasteur never gave any credit to Toussaint and instead said Toussaint’s methods were flawed, and then used widely publicised events to publicly (and successfully) vaccinate against anthrax, taking all the credit for this discovery.

Serendipity in discovery

Chance and serendipity also play a huge role in discovery. But as Pasteur famously said, “luck favours the prepared mind”. There are two parts to discovery by chance. First, there obviously has to be innate curiosity combined the ability to make observations. The second, critical component is a knowledgeable, trained mind. Without a sound understanding of relevant scientific principles, and the training and capability to investigate observations, it is impossible to take an observation and make a discovery.

One of the life-transforming discoveries that came from a chance observation was that of penicillin. Exaggerated stories tell us that a sloppy Alexander Fleming left petri-plates lying around and one day found a fungus which killed bacteria. There’s far more to this story.

Fleming was an exceptional microbiologist with a deep interest in understanding how to control microbial infections. He had dedicated decades of research after World War I to find agents that killed bacteria. He was already famous for his elegant work showing why antiseptic agents actually killed more soldiers in World War I than actual infections by bacteria. This was because anti-septics touched the surface of injuries while infectious bacteria remained deep inside wounds, lying dormant and striking later. He also showed that bodily secretions like nasal mucous or tears could slow down bacterial growth. There couldn’t have been a more prepared mind to make an observation and discover antibiotics.

Fleming had carefully stacked and catalogued many petri plates of bacteria before leaving for a holiday. When he was back, like all excellent scientists, he checked every plate, and found that in a couple of them, fungi had grown. The key observation was that where the fungi had grown, the bacteria around it were dead. While most people would not have noticed this, Fleming had spent years searching for just this phenomenon, so he knew where to go with this observation. He then spent years to isolate and identify penicillin and understand what it did. At that time, there were few (if any) people in the world better prepared than Fleming to make this discovery.

Another great story of discovery by chance that revolutionised the world of physics and transformed modern medicine was Wilhelm Roentgen’s discovery of X-rays. Yet Roentgen was the perfect person to be at a certain place, doing a certain type of experiment, to discover X-rays. He was an outstanding physicist, studying paths of light – electrical rays emitted by cathode ray tubes, much like our fluorescent bulbs. When he shielded the tube with dark paper, he observed that a fluorescent light could be seen on a screen a few feet away. It was his exceptional understanding of physics and optics that enabled him to quickly piece together the fact that an unknown form of light, invisible to the naked eye, and capable of passing through simple substances, was being emitted. This was a great discovery of chance yet ideal for Roentgen to discover.

From chance observations to discovery through relentless pursuits

Having tarnished Pasteur’s reputation earlier, let me now restore it. One of Pasteur’s greatest discoveries is an example of how serendipity coupled with relentless pursuit leads to discovery. This is the discovery of fermentation and subsequently the process of pasteurisation. Any amateur wine- or beer-maker will tell you that it’s rather easy for alcohol to “go sour”. Now, in the mid-19th century, it was obvious that sugary solutions became wine or beer and that you could do that by using yeasts. So why did wine sometimes go sour?

Pasteur, like scientists of his time, used the microscope, to look at the contents of wine. He discovered that sometimes, in addition to oval, budding yeasts, there would be other rod-shaped microbes. Pasteur meticulously proved that the yeast converted sugar to alcohol while the rod-shaped microbes (Acetobacter aceti) converted sugars to acetic acid. Similarly, he identified lactic-acid-producing bacteria in fermenting beets. When these bacteria entered a culture, they could overwhelm the yeasts, take over the culture and produce alcohol-spoiling acids.

He famously said that “alcoholic fermentation is an act correlated with the life and organisation of the yeast cells, not with the death or putrefaction of the cells.” Of course, the Acetobacter also turned out to be very important and we continue to use them to make vinegar from wine.

This work was pioneering, and unraveled how fermentation could be carried out by microbes, with different ends (alcohol, vinegar or lactic acid and yoghurt). Pasteur also systematically showed that during fermentation these microbes didn’t consume oxygen. There was more. Through his careful studies of microbes and fermentation, Pasteur could show that microbes didn’t spontaneously emerge out of thin air (something wildly believed for centuries!), but that living things only came from other living things.

He then used this knowledge to develop the process of pasteurisation, of heating liquids to a temperature high enough to kill the microbes yet such that the liquid wouldn’t spoil. Finally, these observations enabled Pasteur to provide evidence for the “germ theory of disease” (along with his arch-rival, Robert Koch), showing that tiny microorganisms can grow inside a host and cause disease. Thus, though there were a number of chance observations, Pasteur had a fully prepared mind and the relentless drive to take the observations through to discovery.

In all these stories, we see that a discovery is made only when the appropriate tools required for that discovery are invented. Perhaps the stories of great inventions enabling great discoveries are another story.

Sunil Laxman is a scientist at the Institute for Stem Cell Biology and Regenerative Medicine, where his research group studies how cells function and communicate with each other. He has a keen interest in the history and process of science, and how science influences society.

  • Sriram Varahan

    Very nice read !