Physics Teacher's Invention Fair

Charles University, Prague, Czech Republic, 27-29 August 2007

I presented the Keynote lecture at the Physics Teacher's Invention Fair, It was the first lecture of the conference. I didn't have the feeling for how the other teachers would present their materials. So I presented as I would to a group of physics teachers at an AAPT (American Association of Physics Teachers) meeting in the US. It turned out to be the right choice. The presenters who followed me used the same style, accompanying live demonstrations of physics with great images and stories.

My presentation was titled:

Learn Science by Doing Science

You can see an html version of my Keynote presentation by clicking on the above title.

You can see the descriptions of how to do the demonstrations I presented here.

By the end of the conference I realized that the entire Invention fair was summarized as Learning Science by Doing Science, so my keynote was right on target.

My translator was Jan Koupil, it was a pleasure to have a translator who was a physics teacher!

Here are images of my presentation taken by physicist/teacher Zdenka Broklova.


Leos Dvorak, Jan Koupil help me prepare for the conference an hour before my presentation. We were in a classic physics lecture hall that had been outfitted with modern electronic projectors and digital cameras, A great blending of the modern and the traditional.

The lecture hall had a great lecture demonstration table with a granite top. It had European power plugs, overhead projector, cameras, lighting and more, I would love to teach in a lecture hall like this one. The physicists of the faculty pitched in and ran the audiovisual equipment flawlessly.

The first important slides of my presentation said:

A scientist looks at something that everyone has looked at

and sees something that no one has seen


A teacher helps students see things they have never noticed before.


Students ask questions that help teachers see things they have never seen before

On the left notice the laser shining into the bulb, on the right see the speckles.

I wanted to emphasize the role of perception in science. So I chose a perception exhibit that everyone in the audience could see, laser speckle. A simple way to do this is to shine a laser into the backside of a frosted lightbulb. Dark and light speckles appear on the bulb, but when the viewers move their heads the speckles move. For some people they move opposite the way they move their head, for others they move the same way. To observe science we must understand perception and that two people can look at exactly the same phenomenon and see different things

Striking a tempered aluminum rod with a hammer and exploring its vibrations with my fingers. When you pinch a ringing aluminum rod between fingers, the flesh turns the organized vibration of the rod which is heard as sound into disorganized motion of heat. My images show the important physics concept that the rod vibrates back and forth along its length but physicists plot the motion as a sine wave perpendicular to the actual motion. Leos bought the rods for me which made my travels to Prague much easier.

I finished my presentation by exploring the physics of the whirly..of course. Leos had found local sources of corrugated plastic tubes for me. They sand wonderfully when swung about.

I also played the bag whirly, a multicultural representation of my Celtic heritage. I was pleased that I could make my translator Jan and my host Leos laugh with my presentation.

I finished by explaining the physics of the whirly. How turbulent eddies created by air tumbling over the ridges inside the corrugated tube synchronize with the resonances of the tube to produce loud clear musical tones. I also noted that at slow speeds the flow through the tube is laminar, that is a low Reynold's number flow, and so the tube does not sing its fundamental.

People came up during the break time to talk with me about the physics behind my demonstrations and to do the demonstrations themselves.


Leos Dvorak chairman of the Physics Department in the faculty of Mathematics and Physics at Charles University was my fantastic host. I stayed in a Hotel right next to the University. It was just a few meter walk from the hotel to the lecture hall, and a slightly longer walk to the I.P Pavlova metro station which gave me access to the entire city through the fantastic public transportation system of Prague.

Thanks to Leos, Jan and everyone else who made my visit to Prague so wonderful.

Scientific Explorations with Paul Doherty

© 2007

8 September 2007