Does lightning go UP or DOWN? High-speed cameras show the answer!

Does lightning go up or down? How about sideways? Science and high-speed video cameras give us a clear answer to this question, and it's probably not what you'd expect. As a thunderstorm grows, multiple areas of electrical charge form, some positive, some negative. A lightning bolt is born inside of the cloud in between two of these areas of opposing electrical charge. Lightning starts at a single point inside of the cloud, growing in two directions in narrow branching paths called leaders. This bidirectional leader, one end negative, the other positive, lengthens and branches out as it taps into the charged regions of the storm. Here's video from a high-speed camera showing a bidirectional leader growing in a cloud. These in-cloud leaders can move in any direction, up, down, and sideways. Leaders can branch for dozens or even hundreds of miles across large thunderstorm complexes. Lightning strikes the ground when one end of this bidirectional leader, usually the negative end, heads towards the earth. Here's what that looks like on a high-speed camera at 1500 frames per second. So lightning striking the ground moves downward, right? Yes, but that's only part of the story. When the descending leaders get close to the ground, one or more upward leaders form on grounded objects and grow towards the descending leader. When one of these upward leaders connects with a branch of the downward leader, the electrical connection from ground to cloud is complete. This is when a massive sudden white hot surge of current, called a return stroke, races back up to the cloud through the channel. Most of this process happens way too fast for the human eye to discern. What we and most of our normal video cameras can see is just the bright return stroke phase of lightning, but modern high-speed video cameras can show the progression of lightning leaders in vivid detail. These cloud-to-ground bolts were filmed at 6,000 frames per second. You can see the negative leaders descending to the ground, then the bright return stroke when the connection is made. In this shot, you can see the return stroke current pulse racing upward through the channel. This still photo shows some of the unconnected upward leaders near the final strike point. This strike to the Gateway Arch in St. Louis, filmed at 1,500 frames per second, shows the downward moving leaders and the upward moving leader just before they connect for the final strike. So when it comes to lightning, there are a lot of ups and downs, but that's not all. Lightning can also start at the tops of tall objects and move upward into a storm cloud. This is called ground-to-cloud or upward lightning. It's commonly seen from tall towers, skyscrapers, mountain peaks, and even wind turbines. Upward lightning begins as a leader starting at the tip of a tall object, growing skyward. Most upward lightning to tall objects consists of positive leaders. Finally, this video from Chicago shows it all. Upward lightning starting from three of the skyscrapers at the same time, then a downward strike hitting Lake Michigan behind the city, then sideways leaders crawling across the sky. Upward, downward, and sideways lightning all happening in less than one second. This has been Dan Robinson for stormhighway.com. Stay tuned to this channel for more lightning science videos, clips from high-speed cameras, and more.