The kid on the porch is a dinosaur, or a superhero, or something from a video game that the adults handing out candy do not recognize, and around one wrist there is a green plastic bracelet, glowing. Somebody in the house thought about the dark streets and the cars and did the cheap, sensible thing: a tube of glow sticks from the drugstore, cracked and shaken in the kitchen before the first doorbell, one on each child so they can be seen from the road. By nine o'clock the neighborhood is full of small green and pink and blue lights bobbing along the sidewalks, and by morning they are dim and sticky and in the trash. It is the most ordinary object of the night, and also a small chemical plant, sealed, single-use, running a reaction that Baytown could explain as well as any town in the country.
Start with what happens when you bend it. A glow stick is a flexible plastic tube with a thin glass vial inside. The tube holds one solution; the vial holds another. When you snap the tube the glass breaks and the two meet, and you shake it to mix them, and the light starts. There is no battery, no bulb, no heat to speak of. The light is coming directly out of a chemical reaction, and the name for that is chemiluminescence: light from chemistry, the way a firefly does it, the way some deep-sea animals do it, the way no candle or lamp does.
The two liquids are not exotic. One side is a solution of a compound called an oxalate ester, a molecule built around two carbons bonded to each other, each carrying two oxygens, with a larger organic group hanging off each end. Dissolved with it is a dye, and the dye is the part that decides the color. The other side, in the glass vial, is hydrogen peroxide, the same stuff in the brown bottle under the bathroom sink, only stronger. When the peroxide meets the oxalate ester, it attacks it and strips off the end groups and leaves behind a small, strained, unstable ring of two carbons and four oxygens, a molecule that does not want to exist. It falls apart almost instantly into two molecules of carbon dioxide. That falling-apart releases a packet of energy, and the energy is handed to the dye molecule, which absorbs it, holds it for a fraction of a second in an excited state, and then lets it go as a single particle of light. Change the dye and you change the color. The reaction is the same in every stick; the dye is just the translator.
Notice what is missing. A candle makes light by getting something hot enough to glow, and most of what it puts out is heat you cannot see. An old light bulb does the same with a wire. The glow stick skips that step. It goes straight from chemical energy to a photon without heating anything, which is why you can hold it against a child's skin all night. Chemists call this cold light, and it is a rare trick. Almost everything else that shines in the world, from the flare across the bay to the sun, shines because it is hot. The firefly and the glow stick shine because a molecule was handed exactly the right amount of energy and had nowhere to put it but out.
So the glow on your child's wrist is carbon dioxide being made, one molecule at a time, with a photon thrown off for each one. You can prove the chemistry to yourself with a trick every kid learns. Put the stick in the freezer and it dims, because cold slows a reaction down. Put it in a cup of hot water and it blazes, brighter than it was in the package, and dies faster, because heat speeds a reaction up and it runs through its supply. There is only so much oxalate in the tube. The light is a budget. That, in a plastic sleeve, is the whole science of rate and energy that a plant on the channel manages on a scale of thousands of tons: how fast a reaction runs depends on how hot it is, and how much you get out depends on how much you put in, and nothing is free.
Now look at the rest of the costume. The bracelet itself is polyethylene, chosen because it flexes without cracking and does not react with the liquids inside. Polyethylene is made by chaining together ethylene molecules, and ethylene is what an olefins plant makes: a hydrocarbon feed run through furnace tubes at something like 800 to 900 degrees Celsius until the molecules snap and reform. It is the most-produced organic chemical in the world. The candy bag is polyethylene too, or polypropylene, which is the same idea with a slightly bigger building block. The wrappers on the tiny chocolate bars are polypropylene film with a whisper of aluminum. The superhero suit is polyester, which is a chain built in part from ethylene glycol, which is made from ethylene. The mask that smells like a new shower curtain is vinyl, polyvinyl chloride, which is ethylene with a chlorine atom bolted on to every second carbon. The face paint is pigment suspended in mineral oil and petrolatum, both of them fractions of crude, the heavy cousins of gasoline. The candle in the pumpkin is paraffin wax, another fraction. The plastic pumpkin bucket, the fake spiderweb, the bag of cotton-ball ghosts, the tube of fake blood, the glow-in-the-dark skeleton, the insulation on the wire of the string lights: all of it, every piece, came through a cracker or a refinery, and some of it, in all likelihood, through molecules that spent a while on the ship channel.
Call it an inventory rather than a complaint or a boast. Halloween in its modern form is an evening made almost entirely of petrochemistry, and the same is true of most evenings; Halloween just makes it visible because the objects are bright and cheap and everywhere and thrown away by Monday. If you wanted to teach a child what a refinery is for, you could do worse than to empty a trick-or-treat bag on the kitchen table and go through it item by item, asking where each thing came from. The chocolate came from a tree. The peanuts came from a field. Everything else came, at some remove, from a drum on the channel.
The dyes deserve their own word, because they are the beautiful part. A dye molecule that can take a packet of energy and emit it as visible light is a very particular kind of thing. Its electrons have to be arranged so that the gap between their resting state and their excited state matches the energy of a photon we can see, red at the low end, blue at the high end. The green sticks use one dye, the blue ones another, the red ones a third. These belong to the same families of molecules used in highlighter pens and in the dye an eye doctor injects into a vein to watch blood move through the back of your eye on a screen. A glow stick and a retinal angiogram are cousins. The kid on the porch does not know this. He does not need to. But the parent handing out candy might feel something shift, once, if she thinks about it: that the cheap toy on the wrist and the imaging screen in a clinic are running the same physics, and that the physics runs on the same feedstock.
There is a version of the theme of these essays that is grand, that goes from the ship channel to the rocket to the stars. This one is the small version. A single photon, thrown off by a dye molecule in a plastic tube, on a wrist, on a sidewalk, in a town that makes the tube. The photon leaves the wrist and crosses the yard and enters the eye of a driver slowing at the corner, and that is the entire purpose of the object, and it works. The grand version says the universe has found, in us, a way to look at itself. The small version says a driver has found, in a dollar's worth of peroxide and dye, a way to see a child in the road. I am not sure they are different claims.
The night-shift operator, if you asked him, would probably talk about the peroxide. Hydrogen peroxide is a molecule that wants to give up an oxygen, and anything that wants to give up an oxygen is something a plant handles with respect. In a glow stick there is a thimbleful, sealed in glass, and the worst that can happen is a stained shirt. In a plant the same eagerness, scaled up, is what the whole building of procedures and alarms is built to contain. He would look at the bracelet and see a tiny, harmless, well-designed reactor: two reagents kept apart until you want them together, a mixing step, a controlled release, a product you can see. He would think it was a decent piece of engineering for a dollar. He would be right.
Late, after the doorbell has stopped, the parent goes out to bring in the bowl and the porch light, and the street is quiet, and down at the end of it a green dot is still moving, some older kid walking home slow with a pillowcase over one shoulder. The light on his wrist is about half as bright as it was at seven. It has been making carbon dioxide and photons for three hours, more of them than anyone could count, and it has maybe an hour left. He turns the corner and the green dot goes with him, and for a second after he is out of sight it is still there on the inside of the eye, the way a bright thing is, a little chemistry, kept where it was put, telling the dark that someone is there. In the morning it will be a dim tube in the grass by the curb, spent, and nobody will pick it up until the mower does.