Information Theory part 5: History of Static Electricity


Around 600 BC lived
Thales of Miletus, widely regarded as the
first Greek philosopher, as he was the first to give
a purely natural explanation of the phenomena he observed. A key observation
that he made was that certain stones– such as
amber– when rubbed against fur would exhibit a
strange property. The amber seemed to emit
an invisible force which would attract small fibers. He assumed this rendered
the amber magnetic, another force he observed when
playing with lodestones, which are naturally occurring magnets. Many after him observed that
the contact or friction with fur seemed to create an imbalance. Something was
pulled from the fur and transferred
onto other objects. Now, not only did this result in
a small attractive or repulsive force, but also in the
potential for shocks to occur. Once the discharge occurred,
the force disappeared. So the shock was some
form of discharge which reversed the imbalance
created by the friction. Throughout history, we
were also fascinated with lightning bolts, nature’s
most passionate displays of power and aggression. Most cultures assumed
this was a divine force, outside the reach
of human hands, and was therefore
reserved for the gods. Up until the 17th century,
our descriptions of it varied from an invisible,
intangible, inponderable agent, or even threads of syrup
which elongate and contract. And it was Benjamin Franklin
who, in 1750, set out to prove that there was a
connection between lightning and these tiny shocks
due to friction. In the famously dangerous
experiment done alone with his son, he led a
kite into a thunderstorm. And near the bottom,
where the thread was wet, he tied an iron key. And after some time, he brought
his knuckle up to be key, and experienced a
series small shocks, identical to the ones
created by contact with fur. This showed that,
indeed, lightning was simply the same thing
as these household shocks, but on a massive scale. And at this time, people had
begun to divide materials into two categories. One were objects which
would allow, or accept, discharge– such
as gold or copper– which we call
electrical conductors. And interestingly,
these materials are also generally good
at conducting heat. And number two were
objects which would not allow this discharge–
such as rubber, or electrical insulators. These materials also seemed to
insulate the transfer of heat. And we also began trying to
measure this force that Thales had encountered. One way to do this
was to suspend a piece of spongy plant, called
a pith ball, from a thread. And when we rubbed an
insulator against fur and brought it
near the pith ball, it would pull on it,
causing a deflection. If we added more
objects, we noticed this deflection increased, due
to a greater pulling force. We also notice that the shape
of insulators made a difference. Large, thin insulators seemed to
exhibit a much stronger force. And amazingly, it was found
that conductors, such as copper wire, would transmit this
pulling effect over a distance. This was demonstrated
by running a long wire between the pith ball and
the charged insulator. When the object was
brought near the wire, it pulled through the wire
and deflected the pith ball instantly. When we later touch the
wire with our finger, a discharge occurs
and the pulling stops, and the ball is released. Immediately, people
began speculating that this could be the
future of optical telegraphs. And in 1774, French inventor
Georges-Louis Le Sage was one of the first on record
to actually set up this idea. He sent messages through
an array of 26 wires, each wire representing a
letter of the alphabet. When a discharge
occurred at one end, the pith ball would
move at the other. The trouble with his
telegraph was that it only extended between the
two rooms of his house. The power of the deflection
was small and difficult to work with. Though at the time, people
were investigating techniques for generating larger
charge differences in order to amplify the force involved. One improvement popularized
by Alessandro Volta one year later was an
easy way of generating discharges on demand. It was based on the idea that
a charged insulator could introduce, or transfer, a charge
onto a nearby conducting plate. One needed to merely
bring the metal plate close to the insulator, which
would pull on the charge distribution in the
metal plate, resulting in an imbalance, or electrical
tension, in the metal plate. Then one could bring
their finger to the plate, and a discharge would occur. Then the plate is pulled away
using an insulating handle, and an excess charge would
remain trapped in the plate. The plate could then
be discharged at will simply by touching it to a
conductor, such as a finger. And amazingly, this process
can be repeated many times without recharging
the insulating plate. We could then generate many
small discharges at will. And by now, Benjamin
Franklin was focused on finding
out how to trap or store up these discharges. At this time, he still
assumed that electricity was some sort of
invisible fluid, since he knew it could
travel through water. So he assumed that water
inside an insulator could hold electricity. What we now call the
Leyden jar was a glass jar with water
inside and a metal probe running out the top. Franklin also wrapped the
outside in a conductive metal. When he brought a
charged conductor towards the top
probe, a discharge would occur, and stay
trapped in the jar. More importantly
was that the jar could be charged multiple times. Each spark would amplify
the charge separation, or electrical tension,
inside the jar. A good analogy is to think
of the jar as a balloon, and each discharge as
a short jolt of water. After hundreds of iterations,
the tension becomes massive. And to release the
charge, he simply touched the outside
conductor to the top probe. A large discharge occurred. Franklin improved
the design over time, eventually realizing
that the charge was not stored in the water,
but the glass. The water was merely
a conductive path from the probe to the jar. Today, we would
call the Leyden jar a capacitor, or a
charge-storing device. And when he chained
many jars together, he founded he could increase
the capacity even more, and release deadly
bolts of electricity. And over the years, people
focused on more effective ways of building up charge using
friction machines which could be stored in
capacitors and released as spectacular displays
of man-made lightning. And over the next
50 years, people tried to design systems
for sending sparks across greater distances using
longer wires and more powerful discharges. However, sending
electrostatic discharges as a communication
method seemed clumsy, archaic, and was no
improvement over the existing optical telegraphs of the day. They were widely ignored
by government and industry. Though tides were rising–
an electric revolution was just around the corner.

23 Comments

  1. Jacob Manson

    February 16, 2013 at 10:20 am

    very very well done.

  2. isaac0060

    February 16, 2013 at 6:16 pm

    YOU LEAVE US WANTING MORE EACH TIME!!!!!!!!!!!!!

  3. UnPuntoCircular

    February 16, 2013 at 6:42 pm

    I love how you go from the very beginning, explaining the historic context and how the discoveries were made. This is how science must be taught!… Thanks. Your videos are amazing, interesting and highly educational.

  4. Crux161

    February 16, 2013 at 7:08 pm

    Another cliffhanger… Can't wait for the next one!

  5. SuperBase555

    February 18, 2013 at 2:06 am

    Thanks for the fun and educative videos. Can't wait for the next video on the Language of Coins!

  6. Mr. V

    February 18, 2013 at 8:06 am

    Good job!! (Nice cat too!)

  7. JohnDubya

    February 18, 2013 at 10:46 pm

    The cat's reactions are a mix between, "WTF, dude?!" and "Keep doing that, human."

  8. toakleaf

    February 19, 2013 at 1:02 am

    Good video, however, Benjamin Franklin never actually performed the key experiment, as was debunked in episode 283 of "This American Life".

  9. IdleGod

    February 22, 2013 at 5:12 pm

    I think your cat is beginning to hate you. Haha.

  10. Stacy Sosa

    March 3, 2013 at 6:57 pm

    the cat is incredibly cute

  11. Stacy Sosa

    March 3, 2013 at 7:00 pm

    so if you pulled eletrons from the cat, does that mean your cat is positively charged now? Eletric cat?

  12. Quantum War

    April 16, 2013 at 9:54 pm

    yes, indeed, this is actually major explanation of electrostatics

  13. ZelotZim

    May 13, 2013 at 2:05 am

    Cat: I don't know why you strange humans are rubbing stuff on my back, but keep them coming.

  14. Blue

    July 29, 2013 at 1:52 pm

    Extremely interesting and well explained! 🙂

  15. Abhilash Aradhya

    September 3, 2013 at 5:51 pm

    Amazing Explanation!!!!!!!!!!!!!!!!!!!!!!!!!

  16. Knack Wurst

    June 7, 2014 at 4:26 am

    Large flat insulators make cats mad

  17. luis fuentes

    April 19, 2015 at 6:05 am

    this video deserves more views

  18. Gerry McDougald

    October 14, 2016 at 3:40 pm

    Excellent, my class loved it. Thank you!

  19. PeepNSheep

    November 12, 2016 at 12:48 am

    You can sya your cat was "constructively discharged." Ba dump bump

  20. Shaggy b. Defecating

    September 16, 2017 at 9:20 pm

    holy shit these are awesome! thanks Art of the Problem:)

  21. Naterkix S

    November 13, 2017 at 1:14 pm

    Cat: "Mmmmnyah…. I love science, nya…"

  22. Noah Levine

    January 30, 2019 at 9:55 am

    what are those stony sounding instruments in the background? I really like them

  23. MathStarz11

    August 30, 2019 at 5:26 pm

    I never knew I would enjoy a history lesson so much from 6 years ago. Thanks for this content. I'm making my way through your information theory course. It's very insightful.

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