The black cat wants to play with the balloon lol.
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 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,
a [property] he observed when playing with lodestones,
which are naturally occurring magnets.
Many after him observed that 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.
we were also fascinated with lighting 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, imponderable agent –
or even threads of syrup which elongate and contract.
And it was Benjamin Franklin who, in 1752,
set out to prove that there was a connection
between lightning and these tiny shocks due to friction
In a famously dangerous experiment –
done alone with his son –
he led a kite into a thunderstorm.
And near the the bottom,
where the thread was wet, he tied an iron key.
And after some time,
he brought his knuckle up to the key,
and experienced a series of 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 [category included] 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.
[In category] number two were objects
which would not allow this discharge –
such as rubber – [which we call] electrical 'insulators.'
These materials also seem to
insulate [against] 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, [by] a thread.
And when we rubbed an insulator against fur,
and brought it near the pith ball,
[the insulator]would [appear to] pull on [the ball],
causing a deflection [from the ball's normal resting position].
If we added more objects,
we noticed [that] this deflection increased --
due to a greater pulling force.
We also noticed 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 [charged] object was brought near the wire,
[the charge] 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 [or visual] telegraphs.
And in 1774, French inventor, George-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 this 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.
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 induce 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
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.
And 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 'charge-storing device.'
And when he chained many jars together,
he found 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 then 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 the tides were rising.
An electric revolution was just around the corner.
Log in to save your progress and obtain a certificate in Alison’s free Understanding Information Theory online course
Sign up to save your progress and obtain a certificate in Alison’s free Understanding Information Theory online course
Please enter you email address and we will mail you a link to reset your password.