In case you didn’t already know it, lightning travels incredibly fast. Although this video is 33 seconds long, in reality, this event happened in only a little over 0.1seconds. What to us look like a simple flash of light, when slowed down 300x, is really an incredibly beautiful and complex phenomenon.
There are a number of theories about how lightning originates, but all involve a build up of charge in the atmosphere. This, in itself, isn’t what causes lighning. What does is the difference in charge between the atmophere and the ground. To equilise this charge differential, electrons need to flow downhill. This is what we see in the first half of the video. Electrons always like to flow down the path of least resistance, and want to find the shortest distance to the ground. However, the electrons in the cloud don’t know where this is, so we see a random, branching pattern reaching out in all directions. This downstroke is called a negative stepped leader. Once the flowing electrons meet the ground, the current equalises and causes the bright upwards return stroke.
What I find interesting is the same branching pattern that we see on the downwards stroke can also be seen in the burns of victims who have unfortunately been struck by lightning. Its caused by the same phenomenon – electrons flowing to sources of positive charge. Because human skin is pretty homogenous when it comes to electrical resistance, the electrons flow out in all directions causing what is really the most bad-ass scar one can get.