Sunday, April 30, 2023

Lightning Strikes

Environmental & Science Education, STEM, Earth & Space Science, Geophysics, Earth Systems, History of Science, Nature of Science, Models

Ed Hessler

One of the many achievements by Benjamin Franklin was the invention of the lighting rod (His Wiki entry is long; scroll down to "Inventions and Scientific Inquiries" for a discussion of the invention of the lightning rod. 

The invention is based on his extensive investigations into electricity, a proposal of an experimental design on how to test his hypothesis, which was confirmed by a French investigator who used an iron tower instead of a kite (which Franklin later used in his own work), and then again by Franklin who followed his original design which led to the invention as well as some observations on how lighting rods should be used. 

His attention to safety as well as how he collected data by using a physical model which showed that lightning is electrical and then suggesting a technology to protect structures show him to be theoretician, experimenter and technologist, truly an early innovator in researching the natural world.

I had no idea on how complicated a lightning strike is as well as is investigating the moment of the strike. Now thanks to Marcelo M. F. Saba et al., we do and it involved "a serendipitous close observation of a natural lightning flash revealed novel details of the lightning attachment process to residential buildings in highly populated areas." It is also research on how to improve lighting protection system designs.

The paper was published in a technical scientific journal which may be read in full including an abstract, key points, a plain language summary, photographs of the skyline and strikes in black and white.  The photograph of the skyline is important for it shows the buildings involved in the research. The first sentence in the introduction, notes that "the effectiveness of a lightning protection system (LPS) depends on its efficiency to intercept the down coming lightning leader which is usually done by emitting an upward connecting leader (UCL)." The down coming leader is negative and the upgoing leader is positive and the leaders differ in shape (discussed).

Table 1 summarizes measurements and Figure 5 has photographs of the strokes and attachment process as well as of damage to an unprotected chimney and an explanation of the figure. At the end of the paper there is supporting information with three movies if you are interested although I didn't do the work necessary to open them. 

Here are two articles for general readers. The first is from Interesting Engineering by JiJo Malayii includes photographs as well as a link to the press release with a movie. The second is by Nicholas Bakalar for the New York Times (fully accessible) who also includes a discussion of sources (building corners, people) as well as blunt comments by Saba on claims that some lightning rods work better than others. 
Both articles are worth reading.


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