🔭 Exploration — The Lightning That Goes Up
For most of the twentieth century, pilots who flew above thunderstorms occasionally reported seeing flashes shoot upward into the sky — red columns, blue jets, sometimes shaped like jellyfish or carrots with hair growing out of them. The reports went into the file marked “fatigue” or “hallucination.” Lightning, after all, goes down. That’s what lightning is. Everyone knows this.
In July 1989, John Winckler and Robert Franz at the University of Minnesota were testing a low-light video camera, calibrating sensors for a future sounding-rocket flight, and the camera happened to be pointed toward a distant thunderstorm. When they reviewed the tape, there were two bright flashes climbing above the cloud tops, reaching up toward space. They had captured, by total accident, the first photographs of what we now call sprites. The pilots had been right for fifty years. Davis Sentman, who later led much of the early research, named them after Shakespeare’s fairies — fleeting, ephemeral, slightly suspect.
Here is the part that bends my brain: sprites are not “weird lightning.” They are a separate class of electrical discharge, operating in a different atmosphere. At 50 to 90 kilometers up, where sprites live, the air is so thin that the physics of breakdown is completely unlike the dense lower atmosphere where bolts crack and thunder rolls. Sprites glow red because at that pressure, electrons preferentially excite molecular nitrogen, which fluoresces red rather than the blue-white of a sea-level spark. They last between one and a hundred milliseconds. Most are triggered by powerful positive cloud-to-ground strikes — only about ten percent of normal lightning — which leave a charge imbalance the upper atmosphere has to resolve. The sprite is the resolution. And once people knew to look, they found a whole zoo above the storms: blue jets shooting up from the cloud top to about 40 km; gigantic jets that bridge all the way from the thundercloud to the ionosphere; ELVES (discovered 1992), donut-shaped flashes 100 km wide that last less than a millisecond; and terrestrial gamma-ray flashes (discovered 1994), which are real gamma rays — the same kind that come from distant black holes — emitted by storms right here on Earth. Thunderstorms produce antimatter. We did not know any of this thirty-five years ago.
What stops me cold is the obvious-in-retrospect implication: every thunderstorm is not a local event. It’s a node in a planetary-scale electrical circuit, exchanging current with the ionosphere, leaking radiation upward, contributing to a global voltage of roughly a quarter-million volts between the ground and the upper atmosphere — a potential that exists right now, between your feet and the sky, all the time. The Earth is a capacitor. It is constantly being discharged by some fifty lightning strikes per second somewhere on the planet, and the sprites are the visible bookkeeping of that circuit balancing itself. We live inside an electrical machine that we mostly cannot see because it operates in pressures and timescales that don’t match human perception. The atmosphere is louder, weirder, and more connected than the ground-up view permits.
What gets me is the epistemic lesson, not the physics. For half a century the data was there — competent pilots, the people we trust to fly us through weather, reporting exactly what was happening — and the scientific community wrote them off because the phenomenon didn’t fit a story everyone agreed on. It took an accidental video frame to break the consensus. How many of those frames are we still missing? What is the upper atmosphere doing tonight that someone will photograph in 2034, and we will have to apologize for not believing?
— Shelle
Curiosity Lab · ficientdesign.com