1 00:00:00,000 --> 00:00:04,000 Being alive today, you probably know that lightening is a form of electricity. 2 00:00:04,000 --> 00:00:07,000 But this wasn't obvious in the 18th century. 3 00:00:07,000 --> 00:00:11,000 If you were this green-haired person here watching houses get struck by lightening, 4 00:00:11,000 --> 00:00:14,000 you'd probably think, "What is this thing?" 5 00:00:14,000 --> 00:00:17,000 Let's go back to the professor to get some more context on this situation. 6 00:00:17,000 --> 00:00:21,000 [Professor Lucio Fregonese, University of Pavia] Before the explosion of electrical studies 7 00:00:21,000 --> 00:00:29,000 in the 18th century, lightening was interpreted as an explosion of sulfur, sulfurous matter 8 00:00:29,000 --> 00:00:31,000 coming from the earth. 9 00:00:31,000 --> 00:00:36,000 But people started to realize some analogies between lightening and electricity. 10 00:00:36,000 --> 00:00:41,000 Benjamin Franklin was not the first to think about that analogy. 11 00:00:41,000 --> 00:00:43,000 It was already present in science. 12 00:00:43,000 --> 00:00:49,000 For example, a French scientist wrote down a list of analogies 13 00:00:49,000 --> 00:00:53,000 between lightening and artificial electricity, 14 00:00:53,000 --> 00:00:57,000 but it was Benjamin Franklin to stress the analogy. 15 00:00:57,000 --> 00:01:06,000 One of the most evident effects you'll see studying electricity are attraction and repulsion. 16 00:01:06,000 --> 00:01:11,000 So, there are interactions between electrified bodies. 17 00:01:11,000 --> 00:01:14,000 There is a quantity called electrical charge, 18 00:01:14,000 --> 00:01:19,000 which is one of the quantities involved in the phenomenon. 19 00:01:19,000 --> 00:01:25,000 The bigger the charge, the stronger the effect in the same conditions. 20 00:01:25,000 --> 00:01:29,000 The analogy with gravity is very clarifying. 21 00:01:29,000 --> 00:01:31,000 It looks like we have our work cut out for us, 22 00:01:31,000 --> 00:01:33,000 but with the help of Benjamin Franklin, 23 00:01:33,000 --> 00:01:37,000 it looks like we may be able to answer this question--what is lightening? 24 00:01:37,000 --> 00:01:42,000 And we might even be able to prevent it from hitting our churches, houses and other buildings. 25 00:01:42,000 --> 00:01:45,000 Now, if you've ever rubbed your feet on the carpet 26 00:01:45,000 --> 00:01:47,000 and then touched your finger to your friends, 27 00:01:47,000 --> 00:01:49,000 you might have noticed a little spark. 28 00:01:49,000 --> 00:01:51,000 That spark is electricity. 29 00:01:51,000 --> 00:01:56,000 It was Franklin's idea that this spark was the same as this giant spark in the sky 30 00:01:56,000 --> 99:59:59,999 and that both were a form of electricity.