Raft Dinner 2000

Eric Muller and I gave the dinner entertainment presentation at RAFT on October 17, 2000. Here is my short description of what we did. (Pictures will come soon.)

Between the salad and dinner I stood at the podium, held up Eric's book and asked him "Eric what shall we do while we wait for the food to come?

He replied "Good thing you asked Paul" and launched off on our presentations.

He began with Static Sticky Straw everyone at the dinner had been provided with a plastic straw in a paper wrapper. Eric showed them how to remove the straw by tearing off one end of the paper and sliding the straw back and forth until it was warm. Eric warned teachers not to do this with 7'th graders! When the straw was finally removed it stuck to hands and walls. One woman even managed to have it stick to her for 6 minutes! I added that scientists knew that the straw was negatively charged but we didn't know which charge was transferred, we used to think that negative electrons were the mobile charge carriers but recent scanning tunneling microscope studies showed that entire charged atomic clusters could be transferred by rubbing.

We used to know what happened but now, all we know is that we were wrong.
That's science.

I continued with straw oboe. I had made a large model of a straw by rolling up a poster until it was a meter long and 20 cm in diameter. With this giant straw Eric showed the audience how to flatten the end of their straw and I showed them how to cut the ends to the appropriate two lipped shape. Shortly after, we heard the sounds of straw oboes from around the room.
I explained how the sound bounced back and forth in the straw at mach 1.
The length of the straw determined its frequency and pitch.
Eric then blew on a straw oboe as I snipped off the end 1 cm at a time and the pitch went up and up and up. I ended up sniping it close to his lips and still the high pitch rang out loud and clear.

I mentioned that the sound bounced off the open end and that indeed most of the sound was inside the straw and only a little leaked out. Just like a laser, where most of the light was inside the laser and only a fraction leaked out. However there was a way to help more of the sound come out of the straw, add a bell. I brought out a straw oboe with a cone rolled from a sheet of heavy paper. Blowing on it produced a louder sound. Then with a dramatic pause I brought out a straw oboe with a cone rolled from a large poster. The huge cone dwarfed the straw itself but the very loud sound brought a laugh from the audience.

Understanding how sound is conveyed from one material to another is obviously very important so I asked them to find the roll of 2 meters of string at their table and to then tie it into a loop. Eric showed how to wrap the string around their head to make a head harp and soon the guests were strumming and laughing. I then showed them how to share their music with another person by wrapping the string around two heads. The diners noticed that if you pulled the string taught it made a higher pitch. They also noticed they could hear the string touching their cranium but not the strings of others. I told them that this was the perfect acoustic boom box, loud for you but no one else.

"Speaking of coupling", Eric said, " I can control a floating condiment in a bottle by thought alone." I handed him a clear, two-liter bottle full of water with a ketchup packet inside it. He said he was thinking deep thoughts and the diver descended to the bottom of the bottle. Then he thought happier thoughts and the diver rose to the top. People laughed as many figured out what he was doing. Then he gave the bottle to me and walked into the middle of the audience He said he could control the packets at a distance. He said he was thinking depressing thoughts and sure enough the packet sank. We had each table put a ketchup packet into their 2 liter bottles to experiment with the condiment divers. Soon they were laughing and running the divers up and down in their bottles.

Eric explained that to make a condiment diver you had to use the Goldilocks approach. Put the condiment into a bowl of water reject the ones that floated too low, i.e. on the bottom, and the ones that floated too high, but select the ones that floated just right, i.e. barely. Put these these in the bottles and you could easily make them float or sink with a gentle squeeze. Eric explained that squeezing the bottle increased the water pressure, squeezing down the bubbles of air in the packets. The smaller bubbles reduced the buoyancy of the packets and made them sink.

I then balanced the diver, known as a Cartesian diver, in the middle of the bottle, but when I looked away it rose to the top. Even though I couldn't tell I was controlling it by varying my squeezing, I was. Looking closed the feedback control loop. Eric noted that balance was important and guided them to the next activity.

He had each table poke two forks and a toothpick into a cork at their table. They then balanced the entire assembly onto the edge of a wineglass. Cheers and applause rang out around the room as each group succeeded. Eric then had them take out the matches and burn off the end of the toothpick inside the rim of their glass, "It wasn't doing anything." he explained. When the flames reached the glass they went out and Eric got Oohs and Aahs and shouted approval.

Eric then called Mary Simon the director of RAFT to the front of the room. She held a toothpick in her teeth and Eric balanced the fork and cork assembly on the end of Mary's toothpick. She did it first time! (In practice I had taken three tries.) Good job Mary!

Eric finished our performance with a bag blowing contest. He called up John Cassidy my good friend from Klutz Press to compete with Eric in a hot air contest. John and Eric had two 2 meter long bags they were to fill with hot air. Eric gave John a headstart and John puffed mightily into his bag. Eric talked to the audience until John had almost filed his bag and then with one puff filled his bag and tied with John. Proving they both were full of hot air. A fitting climax to our presentation.

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Scientific Explorations with Paul Doherty

© 2000

17 October 2000