The brave Gauls feared nothing more than that the sky would fall on their heads.
Lightning and thunder are indeed frightening natural phenomena. Modern science takes a somewhat more sober view of this, but has still not been able to snatch the final secrets from the powerful electrical discharges in the sky.
One of the pioneers of lightning research is the American naturalist and statesman Benjamin Franklin, who proved in 1752 that lightning is an electrical discharge by directing kites into thunderclouds to trigger lightning. Today everyone agrees that water droplets and ice particles that rise and fall in thunderclouds separate electrical charges and thus generate voltages. However, not all the details of these processes have been clarified beyond doubt, which is understandable given the dangerous nature of the research.
Because during a severe thunderstorm, electric field strengths of over 200,000 volts per meter have already been measured. Theoretically, however, it would take about 3 million volts per meter for a discharge to occur in the well-insulated air. However, humidity probably increases the electrical conductivity in a thundercloud.
In order for lightning to find its way either from cloud to cloud or to earth, a lightning channel must first be created. The air is ionized in a chain reaction by so-called runaway electrons, i.e. it is made conductive. After this lightning bolt has cleared the way, the main discharge can take place, the current strength of which is around 20,000 amperes.
On the ground, this charge is distributed conically in the ground. During this process, temperatures of up to 30,000 degrees even melt the rock, which is occasionally attested to by sand melted into quartz glass, so-called fulgurite. These extremely high temperatures are also responsible for the generation of thunder. Because the air near the lightning bolt heats up explosively and triggers the thunderclap that can be heard many kilometers away.
Since sound travels at only about 300 meters per second compared to lightning-fast light. Can one estimate the distance of an approaching thunderstorm using the time delay between lightning and subsequent thunder, three seconds of time difference correspond to almost exactly one kilometer.
In Germany, 90 percent of thunderstorms occur in summer between June and August. Then, nationwide, around 700,000 to over 1 million flashes of lightning are counted per month. Throughout the year there are about 2 to 3 million.