Lightning!
What’s more fun than fiery magic shooting down from the sky?
6–13–17, Adil (written 7–2–17)
Well, technically, lightning doesn’t just shoot down from the sky — it also shoots up from the ground. We won’t go into too much detail, but here are the very basics of how lightning works:
For reasons that aren’t perfectly understood, negative charges build on the bottom of thunderclouds. During storms, a downward leader goes down with the negative charge, and an upward streamer, coming from grounded objects whose tops are closest to the base of the cloud (e.g. trees, tall buildings, or even people), comes up to meet it with the positive charge. Once the leader connects to a streamer, a process called attachment occurs, and a low-resistance path is formed from cloud to ground. Note that all streamers do not find leaders to connect to and vice versa. After attachment, we get discharge, which, as you might guess, is the massive electrical discharge that is the bright lightning we know and love. The current flows along the plasma channel (#fourthstateofmatter) from cloud to ground, neutralizing the charges. From high-speed videos with tons of frames, we can see that most lightning flashes consist of 3 or 4 individual strokes (all coming after the same attachment), and there can be up to 30!
Cloud-ground (CG) lightning is actually the least common type of lightning (at about 25%; others being cloud-cloud or intra-cloud), but it is the easiest to study and thus best understood. The above process describes the much more common negative CG lightning (stemming from negatively charged cloud bottoms), but there is also positive CG lightning which is more destructive. Positive CG lightning actually originates from the positively charged tops of clouds. In this case, leaders may travel horizontally for several km before yolo’ing towards the ground, thus enabling positive CG lightning to occur in areas with clear or only slightly cloudy skies.
Let’s do some rapid fire (pun intended) facts, now that we have the basics down.
- Average CG bolts are 2–3 miles long and carry 100 million volts of electricity. A bolt’s width is approximately the width of a thumb, but looks bigger because of bright light.
- The temperature of lightning is a balmy 54,000 degrees F, which is fives times hotter than the surface of the Sun. This outrageous temperature causes the surrounding air to rapidly expand, sending out a shock wave which we know as thunder.
- There are ~50 CG lightning strikes on Earth’s surface every second.
- The Empire State Building is hit, on average, 23 times a year.
- Lightning can make trees explode through a pretty cool way. It’s not just direct heating of the bark; in fact, the heat instantly vaporizes the sap and water in the tree into steam, and the steam escapes by exploding the tree. Here is a video of a little tree literally being vaporized:
- There can be lightning not only during thunderstorms, but also during snow storms, dust storms, tornadoes, forest fires, and even volcanic eruptions.
- [Side FF: A thunderstorm with snow instead of rain is actually known as thundersnow, and in thundersnow there is higher likelihood of positive lightning].
- Ball lightning is a super rare and super cool phenomenon, sounding like it came straight out of Pikachu or a Dragon Ball Z episode. Scientists don’t really know how it works, but there have been sightings of luminous spherical balls that hiss, crackle, or explode, and can actually move either fast or slow. These glowing balls of electricity can have diameters ranging from pea-size to several meters, and somehow they last significantly longer than typical split-second lightning flashes. I couldn’t find any reliable video online, but apparently “the first ever optical spectrum of what appears to have been a ball-lightning event was published in January 2014 and included a video at high frame-rate.” Here is the PubMed article in a really legit journal describing the findings (I ain’t got my new database credentials yet to view).
- 9/10 people struck by lightning actually survive, plus they get a cool souvenir. These folks form a strange rash on their skin, which looks like red tree branches. These rashes are known as Lichtenberg figures, and they actually show the path of the electrical discharge that traveled through their skin.
- Roy Sullivan holds the record for being struck most times, at a whopping SEVEN separate bolts. Poor fella got hit in a fire lookout tower, while driving his truck (super rare — it deflected off a nearby tree through his open window, GG), in his front yard, inside a ranger station in Shenandoah National Park, on two separate occasions after running/driving away from storms, and while fishing in a freshwater pool. Amazingly, after this 7th hit, a bear approached him and tried to steal the trout Roy had on his line. But Ol’ Roy had the cajones to smack the bear with a tree branch.
- What are the hottest spots for lightning? Contrary to popular sayings, lightning can and in fact tends to strike the same places. Lake Maracaibo in Venezuela averages about 300 days per year with lightning activity, and the small village of Kifuka in the mountains of the eastern Democratic Republic of the Congo gets a hot 158 strikes per 1 square km per year.
- High-altitutde lightning is a totally different beast. Some fun types include Green Elves, Red Sprites, and Blue Jets. Elves can span over 300 miles in diameter (!!!) and appear like an expanding disc. They occur right over an area of CG lightning, but because they exist for only ~one millisecond, they’re pretty much invisible to the naked eye. They occur about 62 miles above the ground, above thunderstorms. Red Sprites can be as big as 48 x 48 km, and are jellyfish-shaped, appearing after positive lightning. They often occur in clusters about 56 miles above Earth’s surface.
- Blue Jets, on the other hand, are not triggered by lightning. They reach from the top of cumulonimbus clouds to about 25–30 miles above the Earth. They are brighter than Sprites and much less common.
Hope y’all enjoyed this little foray into the fiery goodness that is lightning.
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