JohnD wrote: ↑Wed Sep 29, 2021 8:37 am
70km in one second is slower than a lightning stroke, which goes about 70 MILES in one second.
But I suppose this is going upwards so fighting gravity all the way!
Until the late 18th century it was believed that ringing church bells repelled lightning so many church bells bore the inscription fulgura frango, meaning 'I chase lightning'. During a thunderstorm, bell ringers would run to the bell tower to ring the bells. However, a high tower with a metal bell was in fact about the worst place to be. Between 1753 and 1786 in France, 103 bell-ringers were struck by lightning and killed, resulting in the custom being banned.>>
<<Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, there is a large drop in resistance across the lightning channel. Electrons accelerate rapidly as a result in a zone beginning at the point of attachment, which expands across the entire leader network at up to one third of the speed of light. This is the "return stroke" and it is the most luminous and noticeable part of the lightning discharge.
A large electric charge flows along the plasma channel, from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of the ground. Called step potentials, they are responsible for more injuries and deaths in groups of people or of other animals than the strike itself. Electricity takes every path available to it. Such step potentials will often flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes.
The electric current of the return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground-to-cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures. The rate at which the return stroke current travels has been found to be around 100,000 km/s (one-third of the speed of light).>>
<<Franklin bells (also known as Gordon's Bells or lightning bells) are an early demonstration of electric charge designed to work with a Leyden jar. This was the first device that converted electrical energy into mechanical energy in the form of continuous mechanical motion, in this case, the moving of a bell clapper back and forth between two oppositely charged bells.
This device is named for Benjamin Franklin, an early adopter who used it during his experimentation with electricity. It was discovered by the Scottish inventor Andrew Gordon of Erfurt, Germany. About 1742 he invented a device known as the "electric chimes", which was widely described in textbooks of electricity. Franklin made use of Gordon's idea by connecting one bell to his pointed lightning rod, attached to a chimney, and a second bell to the ground. One of his papers contains the following description: In September 1752, I erected an Iron Rod to draw the Lightning down into my House, in order to make some Experiments on it, with two Bells to give Notice when the Rod should be electrified.
The bells consist of a metal stand with a crossbar, from which hang three bells. The outer two bells hang from conductive metal chains, while the central bell hangs from a nonconductive thread. In the spaces between these bells hang two metal clappers, small pendulums, on nonconductive threads. A short metal chain hangs from the central bell. The central bell's chain is put in contact with the inner surface of a Leyden jar, while the outside surface of the jar is put in contact with the metal stand. Thus, the central bell takes its charge from the inner surface of the jar, while the outer surface charges the two bells on the conductive chains. This causes the bells to have a difference in electrical potential equal to that between the inner and outer surfaces of the jar. The hanging metal clappers will be attracted to one bell, will touch it, pick up its charge, and be repelled; they will then swing across to the other bell, and do the same there. Each time the clappers touch a bell, charge is transferred between the inner and outer surfaces of the https://en.wikipedia.org/wiki/Leyden_jar. When the jar is completely discharged, the bells will stop ringing.>>
It would help, Sa Ji Tario, if you explained obscure words!
A ceraunometer is an instrument used for counting the number of lightning discharges within a specific radius, says the Wiki.
I think it works by receiving the radio noise from the flashes, not by ringing a bell.
PS, Neufer, that picture puts me right off the idea!
Bulletin of the Scientific Instrument Society No. 145
Beccaria’s Ceraunograph and its Modifications
Giovanni Battista Beccaria (1716–1781), the renowned Italian “electrician” taught physics in various Italian cities and finally occupied the chair of experimental physics at the University of Turin. He was an excellent experimenter and his researches in the field of electricity (in which he supported Franklin’s single fluid theory) were among the most remarkable of his time. In 1780, Beccaria described the first lightning recording apparatus and also invented its name – ceraunograph. The term derives from the Greek words κεραυνός (thunderbolt) and γράψω (to write). Beccaria's first ceraunograph was composed of a clockwork mechanism with a vertical axle. A horizontal recording paper disk was inserted on it. The disk was supported by a series of radial straws inserted in the axle. A flat circular box with a circular opening protected the clockwork. The rim of the opening carried a horary annular-shaped scale divided in 12 hours and minutes. A radial line had to be marked on the recording disk in correspondence of the XII (midday or midnight), so that it was possible to have a time reference. The pointed lower end of an aerial conductor (electrode 1) terminated near the upper face of the paper disk, while the upper end of a second wire (electrode 2), which was grounded, ended near the lower face of the disk. The terminals of the two electrodes were aligned along a same radius of the disk, but their distances from the centre were slightly different.
During a thunderstorm, lightning induced voltage surges in the aerial conductor. If a lightning discharge was strong or close enough to the ceraunograph a spark jumped between the gap of the conductors and perforated the paper disk. From the size of the hole it was possible to estimate the intensity of the lightning. From its position on the disk with respect to the XII hour line, it was possible to determine the time of the discharge. Furthermore, according to Beccaria, if the position of the hole corresponded to the upper electrode (1), the lightning occurred downward from the clouds to the earth. On the other hand, a hole aligned with the lower grounded electrode (2) indicated an upward discharge from the earth to the clouds. However, the ceraunograph was a very imperfect instrument. The sparks produced by two or more lightning events in rapid succession proceeded to pass throughout a single hole instead of perforating the paper several times. Furthermore, sometimes the spark did not perforate the disk in correspondence with one of the electrodes, but somewhere between them.