My first-year textbook on geology contained a picture on convection currents and plate tectonics, something like this:

Convection in the deep earth

The teacher, otherwise quite enthusiastic about the book, sighed deeply before he started talking about the picture. “This and similar images,” he said, “are well-meant but flawed. There is a fundamental misunderstanding about plate tectonics contained within them.”

He explained. Lithospheric plates move because of convection currents, so much is correct. However, a common mistake apparently made in these pictures is that they make it look like the fluid movement of the asthenosphere drives the movements of the plates floating on it. This is not true, because the plates themselves are part of the convection current. They move because of two mechanisms: ridge-push and slab-pull, the first being the pushing force created by new material created at the mid-oceanic ridges and the second being the pulling force created by a cool slab sinking back into the asthenosphere. In terms of the picture, the arrows should go right through the plates, rather than under them. More than froth on the fluid asthenosphere, the oceanic lithosphere plates are like the upper part of a conveyor belt.

A hot pan

To illustrate the principle of a convection current, a cross-sectional picture of a saucepan with boiling water was given in the textbook. It looked similar to this:

Forced convection in a saucepan

This seemed to irritate my teacher less. It looks like a simple illustration of how a convection current works. No problem, until I noticed something odd when I was making some vegetable stock. The herbs and froth were flowing towards the middle of the boiling water, rather than from the center to the edge of the pan, as the diagram would predict. In fact, they always did in my kitchen, regardless of the size of the pan or the flame beneath it. So were the authors of the textbook guilty of putting two differently flawed pictures right next to each other? In one of the first chapters of a basic introduction?

What is disregarded in the picture, I think, is that the sides of a pan become hotter than the water, which stays 100^o C. So the water is heated from the sides and the bottom, and can only cool down at the top. This would cause water at the sides to go up, leaving the water in the center with nowhere to go but down. The resulting convection is opposite to the picture, which is therefore wrong. It has nothing to do with plate motion, giving the impression that the textbook got two things wrong in short succession.

A textbook exemplar

The pan of boiling water is a typical ‘exemplar’, a textbook case illustrating a scientific theory. It’s copied and re-used again and again – apparently without testing it. The examples of convection experiments I found on youtube were either ambiguous or showed a current going up along the sides of the container used:

This seemed like a solved case to me, until I cooked water in a thin-walled pan at a windy campsite. The boiling water promptly behaved as the classic diagrams, partially saving at least one of the pictures in my geology textbook. So the direction of convection currents is perhaps not easy to predict. The exemplar is partially wrong in that it does not really describe the everyday situation. I’ve been thinking about the factors influencing it, but regardless of the correct model, it seems odd that only one current direction is ever illustrated. Perhaps creation of convection models and cooking are done by different people?

Dutch broadcasting organization the Evangelische Omroep (EO) has a science program aimed at young people. A non-fact, but when you consider that the EO is completely evangelical, one cannot help but wonder how the evolution issue will be presented. The short but clear answer is: it won’t be presented at all: the program is about empirical testing of everyday experiences, not speciation and adaptation. The EO gained infamy for editing evolution out of BBC documentaries. Representing many Dutch biblical literalists, it is unlikely the organization will publicly denounce creationism, flood geology or intelligent design and thus embrace modern science. But anything that promotes good science automatically promotes evolution, right?

Checkpoint is a program where, in a general sense, questions are asked and a team of teenagers perform tests to answer the questions. The formula is reminiscent of programs like Brainiac, Mythbusters, and even a bit of Jackass. A recurring theme is a boys vs. girls contest, where a boy and girl try their hand at a series of tasks centered around a general skill. The skill ‘multitasking’ was a decisive victory for the boys, winning 4-0.

The word ‘science’ never comes up in Checkpoint, even though the program is a rudimentary example of empirical research. It is this element that makes the program interesting, however. A good example is the question ‘Is it possible to walk on water?’, tackled on th 18^th of july. Good question, especially for an evangelical. First attempt was by attaching floaters to a boy’s feet. He needed two big, unwieldy Styrofoam blocks to stay upright. The second method was less obvious. By mixing large amounts of cornstarch to water until the mixture was saturated, they could quickly walk over the opaque white sludge without sinking. Applying slow or constant pressure on the mixture causes it to behave like a fluid, hitting it quickly with a hammer or the sole of a foot causes it to behave like a solid. A lot of exclamations in the vein of “Hey, that’s cool!” later, one is tempted to believe the audience has learned something about nature. “So that’s how you can walk on water!” the presenter said. Some doubt crept into his last words, so he quickly added: “But this is not real water, ofcourse.” Don’t worry, we get the picture.

Specifically in this example, the viewer learns to appreciate how different rates of pressure applied to a substance leads to different effects. This is a central concept of structural geology. But more generally speaking, teaching kids to explore questions in an empirical manner, rather than relying on a predetermined authority is good practice in combating creationism. We need that, especially from evangelical circles.

The EO is struggling with evolution. Its director, Andries Knevel, recently made it publicly known that he accepts the theory. This led to an outrage among the EO’s members; like all Dutch Omroepen, the organization is semi-governmental and supposed to represent a significant part of the population, which is justified by having a good number of members who show allegiance to the Omroep’s principles. Those members are generally not yet ready for evolution, while an unknown but significant part of the employees are. Checkpoint is a sign that there is a careful but sensible movement towards proper science education in these circles.