John Tyndall and Science Education

This was written in about 1988, I think -- but it is just as relevant today.

This started out as a short "Science Show" piece on John Tyndall and his Tyndall Effect. But as I worked my way through it, searching for the slant that I would use, I found that my chosen theme was taking over. It was developing a life of its own, so that a simple discussion of Tyndall had become a polemic on the ills of science education and the public understanding of science.

Well, who am I to argue with a strong theme, especially as I used to be a science teacher, and I write science books for kids, so I've something of a vested interest in it. But apart from questions of naked self-interest, I've had a life-long interest in science, and I find it hard to understand why other people lack this fascination.

Over the years, I've wondered about this strange and unnatural lack of interest. I've read C. P. Snow on the Two Cultures, and Bill Williams on the Three Cultures, but I still don't know why some people just aren't science-oriented.

I've even listened to Robyn Williams warning us that kids are turning away from science. So far as schoolkids are concerned, it isn't happening in my State, but there is a drop-off when it comes to the tertiary area. The interest just isn't there.

Given the chance, I'd be delighted to find some way of pulling in the masses, to improve the public understanding of science. I've never been able to find out what the answer is, but now I have an idea. It isn't a half-baked idea, but you could reasonably call it a partly-baked idea. I'll share it with you shortly.

As I said, I started out wanting to discuss Tyndall and I ended up with a moral, so let's get back to the beginning, to Tyndall. We'll still get to the moral eventually, and my partly-baked idea.

One of the questions that scientists have been expected to answer for the last hundred years is "why is the sky blue?". It was first posed in Victorian times, and it was answered then. Even so, the question is still asked, and the answer is still largely unknown.

In the course of the past five or six years, I've delved into a lot of nineteenth century science. As I delve, I keep discovering echoes of my own school science education. In the late fifties, much of what I was taught was pre-twentieth century.

One of my criticisms of today's science teaching is that a great deal of what we teach is still pre-twentieth century, even though we don't often realise it. The only way that you can pick this up is to delve through past copies of Scientific American and Nature, or the collected lectures of the Royal Institution to read what scientists were doing and discussing last century.

Or maybe have somebody go back to the sources for you. One of my aims in presenting the historical talks that I do is to put dates on some of the things that are our standard examples of modern science, to put them into a proper perspective, to show where they come from.

To take one example, there's a standard diagram of artesian and sub-artesian wells that I've traced back, so far, to an issue of Scientific American that came out in 1890.

It's a perfectly correct diagram, and I've just asked for it to be re-drawn for my current work in progress, a science text for Year 9 students. The point is that this knowledge, this idea, has been round, essentially unchanged, for a century.

Again, a recent issue of Nature contained a reprint from 1887, relating to a standard demonstration of expansion in a metal bar, one that took my fancy when I first saw it in 1956, demonstrated by a teacher who'd come back out of retirement, just to teach science, one of the real old hands, who once went south with Mawson.

Even though Penguin Watson knew it all, I don't think he was old enough to have written the article in Nature, but you never know... Anyhow, the demonstration's still commonly used today.

You weigh one end of the metal bar down, rest the other end on a thin roller, and heat the bar. As the bar expands, the roller turns, and an indicator on the roller, a straw or some such, slowly rotates as well. A standard experiment, and as I said, one that's been round for a full century.

John Tyndall's answer to "Why is the sky blue?" is an example of a different kind, one that got lost from general public knowledge. I said that it's been with us for over a hundred years, but to track it down, you need to know that the blue sky is caused by the Tyndall Effect.

If you know that much, you can get all of the information you want about the hows and whens, but the question, the answer, and the Tyndall Effect itself, all seem to have dropped from the repertoire of science teaching.

A colloidal suspension contains huge numbers of very tiny particles that are too large to be called dissolved, but too small to be seen by any ordinary microscope. When a beam of light shines through a colloidal suspension, you can see the beam because some of the light is scattered sideways.

You can try this for yourself if you shine a light through a mixture of milk and water. To explain what happens next, we need to know something about the nature of waves, and about the wave nature of light.

Which makes it time for a warning: watch out when physicists start talking like this: the old three-card trick is abroad. Fortunately for you, I'm no physicist, but I do know where the bodies are buried, and I'm only too happy to offer you a loan of my shovel. So, back to the wave nature of light.

To a physicist, light is made of waves, if that is convenient. If it isn't convenient, then light is made up of little particles. And if that won't do, then light is made up of little particles made up of waves. Then they call them wavicles.

Or light is made of green cheese, or whatever helps best to explain what is going on. Is that clear? If it isn't, don't worry. Here, for the purposes of this discussion, light is made of waves. Waves of different wave-lengths. When these light waves pass through milky water, they bounce around all over the place, but something strange happens.

The blue end of the spectrum is scattered, and the red end of the spectrum is allowed to pass, at least comparatively speaking. This, say the physicists, happens because the efficiency of the scattering of the light is inversely proportional to the fourth power of the wave-length.

In simple terms, if you halve the wave-length, you get a sixteen-fold increase in the efficiency with which the light is scattered. When a beam of white light shines through milky water, the blue part of the beam will be scattered sideways, more than the red part.

A person standing to one side will see a blue-ish beam passing through the milky water, but somebody viewing the beam end-on will see a reddish beam. This variable scattering is called the Tyndall Effect, and it explains why the sky is blue.

When the sun shines through the atmosphere on a shallow angle, at dawn and at dusk, red light tunnels right through to us, but blue light is scattered in all directions. Up into space, down to the Earth, all over the place.

When it's dusk here, it's noon somewhere else. People close to midday are right underneath the sun's rays that reach us, and they see the blue light that we miss, coming from all over the sky. At the same time, we see the sun's white light, minus the blue part, and so the sun appears red.

By the same token, when we look at the noon sky, we see the blue light that is being subtracted from somebody else's sunset. And that's why the sky is blue.

Tyndall was able to take a simple matter like that, and fascinate audiences with it, mainly because he didn't just talk about it, he showed people how the effect worked. He did more than explain the colour of the sky, he introduced audiences to the excitements of science.

Not that he rested there. He was also his committed to translating foreign material into English. Characteristically, Tyndall cited Goethe in support of his activities:

Every translator ought to regard himself as a broker in the great intellectual traffic of the world, and to consider it his business to promote the barter of the produce of the mind. For, whatever people may say of the inadequacy of translation, it is, and must ever be, one of the most important and meritorious occupations in the great commerce of the human race.
   --Goethe, Kunst und Altertum

Goethe is best known to us these days as a romantic writer, but he also dabbled in geology, and I rather imagine that his name lives on in the mineral goethite, a hydrated iron oxide.

Goethe also discovered the intermaxillary bone in humans, did some interesting work on plant anatomy, and worked hard at refuting Newton's theory of light. However you look at it, Goethe was an unusual poet, but I digress from John Tyndall.

Not all that much though, for Tyndall was at home with the works of Goethe: not just the scientific works, but the other works as well. Snow's Two Cultures were yet to be thought of, so Tyndall was free to stray as he wished.

He was tireless in bringing the work of Clausius, Helmholtz, Weber and other German scientists to the English public. At a time when so much of physics and chemistry was German, this was a remarkable service for him to perform.

Let's come back to Tyndall's fame as a populariser of science, and here we come at last to my moral. Those who would explain the lack of public enthusiasm for and understanding of "hard" science might do well to think about the old lectures and demonstrations that were so common last century in all of the great centres of science.

These lectures and demonstrations covered new discoveries as they were announced, but there were also shows, mounted by superb performers. In these, older ideas and effects were trotted out for the benefit both of the young and of the previously uninformed.

People don't go out to lectures and demonstrations any more, they stay at home and watch television instead. And what, pray tell, is the content of the typical TV "science" documentary?

Usually it's something biological and environmental: it's all so much prettier on colour TV. Much of it is interesting, desirable and very well done, and it can even be socially useful. Still, lying down with gorillas is hard yakka, but it's not hard science.

There are television shows like our very own "Quantum", that deal in a superb way with the new discoveries, but how long is it since somebody showed the Tyndall Effect on television? How long is it since there was any hard science in an afternoon time slot?

We don't see the old discoveries rediscovered for the benefit of the young any more. And yet the audience keeps changing over, every few years. There are always fresh, new, enquiring minds coming along.

I know that I seem to be digressing from Tyndall again, but I have this sneaking suspicion that it was the wisdom and showmanship of people like Tyndall that inspired several generations in their enthusiasm for science between about 1870 and maybe 1940.

I'm not sure of how that sort of thing would transfer to television, but somebody ought to try. We need modern Tyndalls, people who can ask all those difficult questions, the questions with a bit of meat on them. And we need people to answer those questions in some spectacular fashion in a televisual way.

Why, for example, do decaying nuclei pump out alpha particles when they need to rid themselves of a positive charge? Why don't they emit protons or deuterons instead? Why do hydrofoils work? What are the physics of body-surfing? And why do seagulls follow boats and ships?

Tyndall told us why the sky is blue, though the younger generation have never heard the answer to that question, and nobody has ever explained to me why the sea is blue. The new Tyndall won't earn any Nobel Prizes for Australia, but he or she just might generate a few. Come in, neo-Tyndall, your time is ripe!


This is one of a set of talks which were originally heard on ABC Radio National in Australia. All of the talks are copyright © Peter Macinnis, 2001, but permission will be readily granted on request for educational and most non-profit purposes. Contact Peter Macinnis specifying the talk(s) you want, and the purpose to which they will be put. For the rest of the talks, go to Six Months of Sundays.