Scientific Theories We Got Utterly Wrong: (1) “Phlogiston Theory”

Many people seem to think of the history of science as a steady, unfaltering march from ignorance to enlightenment – but that isn’t quite right.

Along the way, we have faced many impediments; roadblocks that served to hinder the inexorable progress of science – causing it to take the occasional detour down an alluring scenic route.

These roadblocks come in the form of not-quite-right (or downright wrong) scientific theories – theories that were often too irresistible for us prejudicial humans to let go of, like drowning rats clinging to a piece of stinky flotsam.

Our mistake has been our insistence that nature ought to be a certain way, but as we’ve discovered time and again: nature doesn’t care about our intuitions, or our primitive preconceptions. Nature doesn’t care about what was written in a book some centuries ago; she simply is as she is – she won’t be told how she should be.

So, luckily for us, we have the scientific method: an unbiased system of reasoning and empirical testing that – so long as we continue to work within in its strictures – allows us to make progress towards an accurate understanding of reality, in spite of our own biased natures.

Any theory about how the universe works must ultimately be subjected to the scientific method, and, if inaccurate, then regardless of how desperately we cling to it, science will soon advise us, in no uncertain terms, to “try again.

So, though science requires the individual (and highly fallible) scientists to move it forward, it cannot be steered in the direction they want it to go – it only moves in the direction it can go – namely, towards the truth.

One way to think of it is as a ‘pump trolley’ on a railroad; those carts that require you to pump the handle up and down in order to move forward.

No matter how we apes try to maneuver the trolley, it can only go straight. Sure, some of the apes might, at times, be inefficient drivers; failing to pump the handle in unison, such that it comes to an abrupt halt, or moves forward only excruciatingly slowly. But as soon as we come to appreciate how it works, and to operate it smoothly and efficiently, we get the following majestic result:


Anyway, the point of this article (and several related future ones) is not only to draw absurd analogies, but also to show something of real interest. Namely, I want to draw your attention to some specific scientific theories from our past which were eventually found to be disastrously wrong.

These instances are not only fascinating in their own right, but also tremendously instructive: because it is only by hearing about the stumbles and blunders of science that you gain a true appreciation for how it all unfolded.

The first of the blunders I want to discuss is a now superseded scientific theory known as ‘phlogiston theory’, first proposed in the mid 17th century.

What the theory postulates is that there exists a combustible element called phlogiston, that certain materials contain, and which renders such materials flammable.

Despite the fact that it is wrong, the theory has significant explanatory power, and it aligns remarkably well with our intuitions and observations about the phenomenon of burning.

According to the theory, when you burn, say, wood, what is happening is that the phlogiston it contains is being released into the air, and this outpour of phlogiston is what you see and feel as the flames of the fire.

Then, once the wood has been burned to ashes, you would say the remaining substance has been ‘dephlogisticated’ – since is has released all of its phlogiston, and is therefore unable to ignite again.

The theory also readily handles another commonly observed phenomenon – the ability to extinguish a flame by placing a container over it.

When you place a bowl over a candle, the reason the flame is extinguished is because air can only store a certain amount of phlogiston – so the little pocket of air trapped in the container quickly becomes saturated with it, thus no more can be released from the candle, and it burns out.

The theory also ties in with how plants work; they were said to absorb and use phlogiston from the air – which explains why the air doesn’t eventually spontaneously combust, and also why plant matter is so readily combustible.

Phlogiston theory prevailed as the dominant understanding of fire (and also, rust – which was thought of as a slower process of burning; i.e. release of phlogiston) for at least a century, and it is not too difficult to see why.

The theory allows one to formulate a robust model in their mind of this phlogiston substance; how it is absorbed and released by materials – explaining rust and fire in a way that satisfies our intuitions, and always remains an impressively cohesive, internally consistent picture.

And this is no coincidence; the reason phlogiston theory works so well is because it is essentially the theory of oxygen played in reverse. It wasn’t phlogiston being released by the processes of burning or rusting – it was oxygen being absorbed.

And a burning candle wasn’t extinguished because the air became saturated with phlogiston, but because it was depleted of oxygen.

The picture people had in their heads about the flow of phlogiston is analogous to our original view of the flow of electricity – we supposed that it was the positive charges moving around one way, but it was actually the negative charges moving the other way.

So it seems unfair to derogate phlogiston theorists as having been completely and utterly wrong, since they almost weren’t.

But unfortunately, posterity doesn’t tend to recognize theoreticians who were almost right, but exactly wrong (sorry Johan J. Becher).

The theory began to unravel after it was discovered that some materials increased in mass when burned (in reality, because of the addition of oxygen), rather than decrease, as expected. Some people proposed that this was because phlogiston could have negative mass – but as soon as you start twisting the theory in order to align it with observation, that’s when you know you’re in trouble.

In the end, phlogiston theory died because it was superseded by a much grander worldview – one that proposed the existence of an array of many different elements. These new elements, discovered in droves following the work of pioneering chemists like Joseph Priestly and Antoine Lavoisier, were observed to react with each other in a variety of complex and wonderful ways – including the various interactions with oxygen which could account for everything phlogiston theory purported to.

Thus, the scientific method – the continual refining of theories in accordance with empirical observation – won the day once again. With phlogiston out of the way, we had a much broader, more fundamental picture of the elemental world to work with.

Closing thoughts

In school, we are typically told the way things are; for example, we are introduced to the periodic table of elements quite matter-of-factly, almost as though it’s abundantly obvious that this is the way the world is.

What we miss is the fact that science has always been an endearingly human affair; one characterized by endless mistakes and corrections where, only slowly, and clumsily, did we come to know how the world works.

Modern theories weren’t always as neatly packaged as they appear to us now – they evolved gradually, and only through the combined efforts of many fallible scientists.

Just look at Mendeleev’s early attempts at developing the periodic table – the paper is replete with scribbles, after he tried various different arrangements and made many mistakes. He got there in the end, but in the manner of a flawed human, which is to say, the manner in which all science has progressed.

Thus, the modern, pristine periodic table isn’t the true picture of science – this is.

And this picture is one I would like to illustrate by continuing to explore some of the most interesting historical blunders in the history of science. So, if such a portrait of science is one you’d like to see, stick around for more future posts!

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