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Electrostatic telegraphs (case study)

Long before the internet people thought about sending information along wires using static electricity. Created by Brit Cruise.

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Video transcript

Around 600 BC 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 observations he made was that certain stones such as amber when rubbed against fur would exhibit a strange property. The amber seem to emit an invisible force which would attract small fibers. And he assumed that this rendered amber magnetic another force he observed when playing with lodestone which are naturally-occurring magnets. Many after him observed that the contact or friction with fur seem 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 with some form of discharge which reversed the imbalance created by the friction. Throughout history we're also fascinated with lightning bolts. Nature's most passionate displays of power and aggression. Most cultures assume 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 along gate and contract. And it was Benjamin Franklin, who in 1752 set out to prove that there is a connection between lightning and these tiny shocks due to friction. In a famously dangerous experiment done alone with his son, he let 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 the key experienced the series of small shocks identical to the ones created by contact with fur. This showed that indeed, lightning was simply the same thing is these household shocks but on a massive scale. And at this time people have 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. 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 seem 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 the piece of spongy plant called the 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 had more objects we noticed deflection increased due to a greater pulling force. We also noticed that the shape of insulators made a difference. Large thin insulators seem to exhibit a much stronger force. (soft bell ring) 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 in 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 touched the wire with our finger discharge occurs and the pulling stops and the ball is released. Immediately people began speculating that this could be the future optical telegraph. In 1774 French inventor George Louis Le Sage was one of the first one to record 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 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 amplified a force involved. One improvement popularized by Alessandro Volta one year later was an easy wave generating discharges on demand. It was based on the idea that a charged insulator could induce or transfer the 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 in it discharge would occur then the plate is pulled away using insulating handle and an excess charge would remain trapped in the plate to play could then be discharged at will simply by touching it to a conductors 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 with some sort of invisible fluid Since we knew it could travel through water so we assume that water inside in insulator could hold electricity. What we now call the Leyden jar was a glass jar with water inside and a metal probe running at the top. Franklin also wrapped the outside in a conductive metal. When he brought a charge 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 for electrical tension inside the jar. A good analogy is to think of the jar as a balloon and each discharge as a short jolt water. And after hundreds of iterations the tension become massive. And to release the charge he simply touch the outside conductor to the probe. A large discharge occurred. Franklin improved the design over time eventually realizing that the charge was not stored in the water but glass. The water was merely a conductor 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 volt of electricity. And over the years people focused on more effective ways a building up charge using friction machines which could then be stored in capacitors and relief the 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 telegraph of the day. They were widely ignored by government and industry. Though the tides were rising. An electric revolution was just around the corner.