Dream Muse
This was sort of a half-awake half-asleep muse that came to me as I was waking up one morning, a few years ago. It begins with an actual event the day before at the Museum of Science, where I had hauled out our desktop model of a Van de Graf Generator to demonstrate to a visitor.
What's a Van de Graf Generator, you ask?
It's a lightning bolt machine. It has a vertical tube with a conveyor belt running from the base to a metal dome at the top of the tube. A metal comb brushes against the conveyor belt at the bottom. Another metal comb brushes agains the conveyor belt at the top and connects to the metal dome. As the conveyor belt runs, it carries electrons up to the dome, where they collect like pennies in a piggy bank. The brushing combs work just like your shoes when you walk across the carpet on a dry winter's day, and your body builds up a static electric charge. When the static electric charge on the dome is great enough, it discharges with a spark, just like when you touch a metal doorknob after shuffling across the carpet in your winter mocassins. A well-designed Van de Graf Generator can build up tens of thousands of volts of electric charge, and throw a pretty good spark. The big Van de Graf Generator in the Theater of Electricity at the Museum of Science can throw a lightning bolt a good 10 feet.
But enough of the technology sidebar. Back to our story...
In the dream muse, I leave the Museum at the end of the day with a friend, bringing the Van de Graf Generator along. As we are walking down the street, we come to the parlor of a psychic, Madame Leba, who does 'readings'. I am skeptical of such nonsense, but my friend thinks it would be fun to try it out, so we go in.
There is the standard round Seance Table, with Madame Leba holding forth at the head of the table. She asks each of us to put some personal object on the table, so I pony up the Van de Graf Generator. My friend rolls her eyes, and Madame Leba looks a little apprehensive, but what the hey?
The lights dim, some eerie music wells up, and the Seance begins. Pretty soon the table begins to rise. I'm feeling a bit mischievous, because I know how this trick is done. I switch on the Van de Graf Generator (which I had plugged in when the lights were dimmed). It begins to hum as the static charge builds up on the dome. With the music playing, it's hard to hear the humming motor of the Van de Graf Generator.
Now the thing about Van de Graf Generators is that they can throw a pretty good spark -- up to a foot or more for one this size. And they only discharge to something that is grounded.
I know that Madame Leba is levitating the table by means of metal rods strapped to her wrists and extended into receiving tubes fastened to the underside of the table. It's an old trick. But it also means that she effectively has a pair of lightning rods concealed beneath the table top and running from the edge of the table to a point near the spot where I had placed the Van de Graf Generator. It's a thin, light table top. The table has to be light for her to be able to levitate it without straining. The screws that hold the receiving tubes to the underside of the table practically stick up through the surface of the table where Madame Leba is sitting. Within a few seconds, the charge builds up on the dome of the Van de Graf Generator.
Suddenly, there is a look of horror on Madame Leba's face. Zap! The Van de Graf Generator discharges a lightning bolt which hits one of the screws embedded in the underside of the table top, discharging the current through the metal rods strapped to Madame Leba's wrists. She is shocked, shocked! I giggle. This is the best Seance one could have hoped for.
Madame Leba is incensed. She stops the Seance and ejects me and my friend. Then she locks the door of her parlor and puts a 'Closed' sign on the door as we walk away, laughing hysterically.
What's a Van de Graf Generator, you ask?
It's a lightning bolt machine. It has a vertical tube with a conveyor belt running from the base to a metal dome at the top of the tube. A metal comb brushes against the conveyor belt at the bottom. Another metal comb brushes agains the conveyor belt at the top and connects to the metal dome. As the conveyor belt runs, it carries electrons up to the dome, where they collect like pennies in a piggy bank. The brushing combs work just like your shoes when you walk across the carpet on a dry winter's day, and your body builds up a static electric charge. When the static electric charge on the dome is great enough, it discharges with a spark, just like when you touch a metal doorknob after shuffling across the carpet in your winter mocassins. A well-designed Van de Graf Generator can build up tens of thousands of volts of electric charge, and throw a pretty good spark. The big Van de Graf Generator in the Theater of Electricity at the Museum of Science can throw a lightning bolt a good 10 feet.
But enough of the technology sidebar. Back to our story...
In the dream muse, I leave the Museum at the end of the day with a friend, bringing the Van de Graf Generator along. As we are walking down the street, we come to the parlor of a psychic, Madame Leba, who does 'readings'. I am skeptical of such nonsense, but my friend thinks it would be fun to try it out, so we go in.
There is the standard round Seance Table, with Madame Leba holding forth at the head of the table. She asks each of us to put some personal object on the table, so I pony up the Van de Graf Generator. My friend rolls her eyes, and Madame Leba looks a little apprehensive, but what the hey?
The lights dim, some eerie music wells up, and the Seance begins. Pretty soon the table begins to rise. I'm feeling a bit mischievous, because I know how this trick is done. I switch on the Van de Graf Generator (which I had plugged in when the lights were dimmed). It begins to hum as the static charge builds up on the dome. With the music playing, it's hard to hear the humming motor of the Van de Graf Generator.
Now the thing about Van de Graf Generators is that they can throw a pretty good spark -- up to a foot or more for one this size. And they only discharge to something that is grounded.
I know that Madame Leba is levitating the table by means of metal rods strapped to her wrists and extended into receiving tubes fastened to the underside of the table. It's an old trick. But it also means that she effectively has a pair of lightning rods concealed beneath the table top and running from the edge of the table to a point near the spot where I had placed the Van de Graf Generator. It's a thin, light table top. The table has to be light for her to be able to levitate it without straining. The screws that hold the receiving tubes to the underside of the table practically stick up through the surface of the table where Madame Leba is sitting. Within a few seconds, the charge builds up on the dome of the Van de Graf Generator.
Suddenly, there is a look of horror on Madame Leba's face. Zap! The Van de Graf Generator discharges a lightning bolt which hits one of the screws embedded in the underside of the table top, discharging the current through the metal rods strapped to Madame Leba's wrists. She is shocked, shocked! I giggle. This is the best Seance one could have hoped for.
Madame Leba is incensed. She stops the Seance and ejects me and my friend. Then she locks the door of her parlor and puts a 'Closed' sign on the door as we walk away, laughing hysterically.