I’ve posted a new episode on my podcast.

Title: Science Teaching Tips
Episode: 16. Marshmallow Puff Tube

Newton’s Laws were never so tasty. Exploratorium staff educator Don Rathjen shows us how to demonstrate ideas about force using a file folder and a marshmallow.
More of Don Rathjen’s activities

I am a science education and communications consultant -- view my website for my full range of services.

Since I’m now employed as a science education researcher, I’m learning a lot about how people are taught, and how that affects how they learn. People have found some really interesting stuff in this field, and here are a few of them.

For one, in traditional physics lectures, it’s found that students learn, on average, about 25% of the concepts that they didn’t already know about force and motion (Hake, using Force Concept Inventory — PDF here). Wow. That’s not as much learning as we’d like.

Eric Mazur at Harvard was skeptical of these results. Not at Harvard, he thought. But when he measured his students’ learning, he found similar results. Why was this? He found that students could do the calculations just fine, but they didn’t really get the concepts. In fact, when he phrased a problem in a conventional way (like calculating the voltage across a resistor in a complicated circuit), about 69% of the students got it right. But when he showed them a similar circuit — but with lightbulbs instead of resistors — and asked which lightbulb would get dimmer… only 49% were able to answer that question correctly. So they can do the calculations, but don’t know the concepts.

One traditional model of learning is that students heads are empty and can be filled by good explanations and content. This is the “transmissionist” way of thinking about things.

Another way of thinking about it is that students construct their own meaning through active engagement. What that means is that students need to be really working through the ideas for themselves by talking about them with each other and thinking about them on their own. One way to do this is through Mazur’s Peer Instruction, which I’ll write about in another post. Basically, he asks students concept questions throughout lecture, and they vote on the answer using radio-frequency “clickers,” and then discuss the answers with their neighbors until everybody understands the right answer. This kind of instruction has been shown to increase the amount of learning that takes place in lectures (more than that pitiful 25%).

I am a science education and communications consultant -- view my website for my full range of services.

I’ve posted a new episode of my podcast, Science Teaching Tips
15. Lucky Break. First year of teaching story #2.

A lucky veteran teacher tells how she got started teaching, with a supportive school and helpful predecessor. This episode is one in a series of several stories of the first time in a difficult profession.

I am a science education and communications consultant -- view my website for my full range of services.

There’s this myth floating around that polar bear fur is fiber optic. It’s not. It’s not it’s not it’s not.

The myth goes like this… polar bears are white, but they have to keep warm in the winter. But white reflects light and heat, so how do they do it? By having fiber optic fur. “Fiber optics” are a type of “light pipe” that channels light extraordinarily well, sort of like an electric wire does for electric current. So, this is supposed to heat them up by channeling light to their black skin.

This is based on research that showed that polar bears are white to you and me, but don’t emit any ultraviolet (UV) light (they’re black in the ultraviolet). They thought the UV radiation was being absorbed by fiber optics and transported to the skin. It turns out instead that polar bear fur just absorbs UV on its own because of what it’s made of. So this is an example of an early, incorrect science report getting circulated and taking hold in the popular mind.

This myth gets perpetuated by the fact that polar bear fur is hollow. Fiber optics are also hollow, but not every hollow thing is a fiber optic (this is like the “a square is a rectangle but a rectangle isn’t always a square” thing).

Paul D. has an SEM picture of polar bear fur on his website (and some more information).

I was interviewing a scientist/economist (who does a lot of popularization of science) once and he mentioned that “polar bear is fiber optic” as he was discussing solar energy. I told him that, indeed, I had only recently found out that that is a myth, and asked him to retake his answer without that reference (since this was for radio). He did, but I thought his manner was odd. I saw him speak — for a LIVE TELEVISION BROADCAST — on solar energy a few weeks later. And while I sat there flabbergasted in my seat, he repeated the “polar bear is fiber optic” myth right there in front of the cameras!

Do a Google right now for “polar bear fur fiber optic” and you’ll find a variety of links, many of which shed doubt (and some which don’t) on this myth. I wonder if he researched the topic and found something compelling to convince him it was true, or whether the story was just too good to drop? So, this is how myths are perpetuated.

I am a science education and communications consultant -- view my website for my full range of services.

Have you been told that glass is a liquid? I remember back in 10th grade and my teacher told me that old windows were thicker at the bottom than at the top, showing that glass flows, veeerrrry slowwwwly.

While I was at the Exploratorium, this myth was debunked for me by my mentor Paul Doherty. It is true that many old windows are thicker at the bottom than at the top, but it’s not because glass flowed over time and puddled at the bottom. Old windows were made by spinning the molten glass and then cutting it into panes, resulting in glass that was thicker at one end than the other. In fact, later observations noted that some ancient glass is thicker at the top than at the bottom. It just depends on how the window was placed.

Paul notes on his website that: Room temperature glass has a viscosity of 10²² poise. The viscosity of a liquid controls how fast it flows under gravity. (SAE 30 motor oil has a viscosity of about 1 poise, water is 0.01 poise.) The viscosity of glass is so high that you could wait the entire age of the universe and see no measurable thickening of the glass under earth gravity.

Note that the definition of a solid is a material with a viscousity greater than 13 poise.

Of course, as Paul likes to say, “it’s more complicated than that.” Some people say that glass is both liquid and solid because when you look at the underlying structure of it, it has properties of both. But in terms of its material properties (does it flow!?) it can be classified as a solid. But the answer really isn’t that cut and dried.

Here is a link with more information than you’ll probably want to know.

I am a science education and communications consultant -- view my website for my full range of services.

I’ve posted a new episode of my podcast, Science Teaching Tips
Episode: 14 – Through the Looking Glass

How big does a mirror have to be for you to see yourself in it? Exploratorium senior staff scientist Thomas Humphrey describes an activity you can use in your classroom to investigate simple optics.

I am a science education and communications consultant -- view my website for my full range of services.