Atmospheric Electricity - History

History

The detonating sparks drawn from electrical machines and from Leyden jars suggested to the early experimenters, Hauksbee, Newton, Wall, Nollet, and Gray, that lightning and thunder were due to electric discharges. In 1708, Dr. William Wall was one of the first to observe that spark discharges resembled miniature lightning, after observing the sparks from a charged piece of amber.

In the middle of the 18th century, Benjamin Franklin's experiments showed that electrical phenomena of the atmosphere were not fundamentally different from those produced in the laboratory. By 1749, Franklin observed lightning to possess almost all the properties observable in electrical machines.

In July 1750, Franklin hypothesized that electricity could be taken from clouds via a tall metal aerial with a sharp point. Before Franklin could carry out his experiment, in 1752 Thomas-François Dalibard erected a 40-foot (12 m) iron rod at Marly-la-Ville, near Paris, drawing sparks from a passing cloud. With ground-insulated aerials, an experimenter could bring a grounded lead with an insulated wax handle close to the aerial, and observe a spark discharge from the aerial to the grounding wire. In May 1752, Dalibard affirmed that Franklin's theory was correct.

Franklin listed the following similarities between electricity and lightning:

• producing light of a similar color;
• rapid motion;
• being conducted by metals, water and ice;
• melting metals and igniting inflammable substances;
• "sulfurous" smell (which is now known to be due to ozone);
• magnetizing needles;
• the similarity between St. Elmo's Fire and glow discharge.

Around June 1752, Franklin reportedly performed his famous kite experiment. The kite experiment was repeated by Romas, who drew from a metallic string sparks 9 feet (2.7 m) long, and by Cavallo, who made many important observations on atmospheric electricity. L. G. Lemonnier (1752) also reproduced Franklin's experiment with an aerial, but substituted the ground wire with some dust particles (testing attraction). He went on to document the fair weather condition, the clear-day electrification of the atmosphere, and the diurnal variation of the atmosphere's electricity. G. Beccaria (1775) confirmed Lemonnier's diurnal variation data and determined that the atmosphere's charge polarity was positive in fair weather. H. B. Saussure (1779) recorded data relating to a conductor's induced charge in the atmosphere. Saussure's instrument (which contained two small spheres suspended in parallel with two thin wires) was a precursor to the electrometer. Saussure found that the fair weather condition had an annual variation, and found that there was a variation with height, as well. In 1785, Coulomb discovered the electrical conductivity of air. His discovery was contrary to the prevailing thought at the time, that the atmospheric gases were insulators (which they are to some extent, or at least not very good conductors when not ionized). His research was, unfortunately, completely ignored. P. Erman (1804) theorized that the Earth was negatively charged. J. C. A. Peltier (1842) tested and confirmed Erman's idea. Lord Kelvin (1860s) proposed that atmospheric positive charges explained the fair weather condition and, later, recognized the existence of atmospheric electric fields.

Over the course of the next century, using the ideas of Alessandro Volta and Francis Ronald, several researchers contributed to the growing body of knowledge about atmospheric electrical phenomena. With the invention of the portable electrometer and Lord Kelvin's 19th century water-dropping condenser, a greater level of precision was introduced into observational results. Towards the end of the 19th century came the discovery by W. Linss (1887) that even the most perfectly insulated conductors lose their charge, as Coulomb before him had found, and that this loss depended on atmospheric conditions. H. H. Hoffert (1888) identified individual lightning downward strokes using early cameras and would report this in "Intermittent Lightning-Flashes". J. Elster and H. F. Geitel, who also worked on thermionic emission, proposed a theory to explain thunderstorms' electrical structure (1885) and, later, discovered atmospheric radioactivity (1899). By then it had become clear that freely charged positive and negative ions were always present in the atmosphere, and that radiant emanations could be collected. F. Pockels (1897) estimated lightning current intensity by analyzing lightning flashes in basalt and studying the left-over magnetic fields (basalt, being a ferromagnetic mineral, becomes magnetically polarised when exposed to a large external field such as those generated in a lightning strike).

Using a Peltier electrometer, Luigi Palmieri researched atmospheric electricity. Nikola Tesla and Hermann Plauson investigated the production of energy and power via atmospheric electricity. Tesla also proposed to use the atmospheric electrical circuit to transmit energy wirelessly over large distances (see his Wardenclyffe Tower and Magnifying Transmitter). The Polish Polar Station, Hornsund, has researched the magnitude of the Earth's electric field and recorded its vertical component. Discoveries about the electrification of the atmosphere via sensitive electrical instruments and ideas on how the Earth’s negative charge is maintained were developed mainly in the 20th century. Whilst a certain amount of observational work has been done in the branches of atmospheric electricity, the science has not developed to a considerable extent. It is thought that any apparatus which might be used to extract useful energy from atmospheric electricity would be prohibitively costly to build and maintain, which is probably why the field has not attracted much interest.