Glow

Glow grew up in a family of fireflies who had always watched the sun.

Every dawn, her elders would gather on a high branch and turn their faces to the sunrise, and the warmth would arrive on their skin the very same instant the light did. "It puzzled little me so much," Glow remembers. "The air between us and the sun was freezing cold — but the warmth still reached us. How? There's nothing out there but empty space for millions and millions of miles!"

Then her grandmother pointed at the sunbeam falling across their branch. "The warmth doesn't swim through the air, little light," she said. "It rides on the light. Light needs no road. It crosses the empty dark all on its own — and carries the sun's warmth right to your face." Glow felt it then, warmth landing on her skin at the speed of light itself. "That was the day I understood," she says, her belly glowing bright. "Heat doesn't always need a thing to travel through. Sometimes it just shines across the nothing. And I've chased that glow ever since."

When Glow was twelve, she walked to HeatForge. Kelvin, her mentor, asked her, "What is radiation?"

Glow answered at once, spots flickering. "Heat travels as light — across empty space. Every warm thing glows, mostly with invisible heat-light. And that light needs nothing to travel through, which is how the sun's warmth crosses millions of miles of empty space to reach us. It's glow-craft."

Kelvin smiled. "You are appointed."

In her workshop, Glow loves to show it. She holds up a warm mug to her heat-detector, and the screen lights with the invisible heat-light pouring off it — "See? Even things that don't look like they're glowing are, in heat-light." Then she teaches the secrets. Every warm thing radiates — the warmer it is, the more it glows; get something hot enough and the glow becomes visible: red, then orange, then white. Radiation needs no medium — no air, no water, no touching; it crosses a vacuum, which is exactly why the sun can warm us across empty space (and why conduction and convection can't do that job). Surfaces matter — she uses her mirror to show that shiny, light-colored surfaces bounce heat-light away (which is why a space blanket is shiny, and why light clothes feel cooler in summer), while dark, dull surfaces soak it up (which is why a black car bakes in the sun). And she's careful about the big idea: "Radiation isn't a magic trick or a mysterious ray. It's just light — the same family as the light you see by — carrying energy from a warmer place to a cooler one. When it lands on you and gets soaked up, its energy becomes your warmth. That's all a campfire is doing to your face across the cold night air."