I’m a night owl. If I’m up to see the sun rise, something has gone horribly wrong at one end of my day or the other. And while I’m theoretically there to see the sunset, in practice I hardly pay attention to it, unless I’m outside for some reason.

This luxury is brought to me by ubiquitous artificial lighting.

As we just did with fuel sources, let’s rewind the clock. For most of human existence, our main source of light has been the sun. When it went down, we pretty much had to close up shop. Even if the moon was full and the night was clear — which can produce remarkably bright light — we were exceedingly vulnerable to nocturnal predators, who can see vastly better in dim conditions than we can. Safer to stay in the cave, or wherever you’ve taken shelter.

Fire changes that equation. Fire makes it possible to keep going after the sun’s headed to bed, continuing your unfinished work or relaxing after a hard day’s toil. And that changes our behavior quite a lot.

The initial form of this was the campfire or hearthfire, but burning enough wood, turf, or dung to see by is a flagrant waste of fuel. Torches, that ubiquitous feature of fictional dungeons and handy tool for explorers, do better — at least when they’re not just a stick burning at one end, the way they’re sometimes depicted. A proper torch has one end wrapped with some kind of material, often fabric soaked in a flammable substance; nicer ones have a collar below the burning end that helps keep droplets or burning fragments from falling onto the holder’s hand. How long they’ll burn for, though, depends on the size of that wad, and what it consists of. And either way, you’ve got a big open flame, which can be pretty dangerous.

That’s why torches have been less common in reality than they are in fiction. Vastly more common are lamps, reservoirs of flammable oil with a textile wick. These let you control the size of the flame by controlling the length of the wick, and you can keep refilling the oil without having to extinguish the flame or get a new lamp. Making a primitive one is dead easy; you just need a shallow dish and something to keep the wick from falling in completely. And the list of oils you can burn is practically endless: plant sources like olive, sesame, flax, castor, or various nuts, or animal ones like fish oil, butter, ghee, or blubber, which was incredibly common during the heyday of whaling. Fancier designs include things like glass shields to shelter the flame from being blown out, and to prevent things like people’s sleeves or hair from accidentally catching fire. (That danger used to be very real.)

Go from liquid to solid, and you have the basic concept of a candle: still a wick inside a flammable substance, but this time in more vertical form. Much like parchment vs. papyrus, the increased use of candles in Europe seems to have been driven by the loss of Mediterranean olive oil after the collapse of the Roman Empire. People turned instead to tallow, i.e. rendered animal fat. The very cheapest candles were rushlights, the pith of a rush plant soaked in fat or grease; they burned incredibly fast and not very bright, but were also so inexpensive you could make a ton of them. Tallow dips with cloth wicks were usually better, but pricier, and both they and rushlights stank of the animal fat used to make them. The very best candles were made of beeswax, whose scent is quite pleasant, but generally only the nobility and the church could afford them. The rise of whaling led to spermaceti candles, which burned brighter and were less prone to bending on hot days; with the Industrial Revolution came other alternatives, like modern paraffin wax. But until we started making braided wicks, which basically self-trim, it was necessary to regulate wick length with scissors to make them burn well.

In Europe, the introduction of gas lighting was a huge advance — but also a short-lived one, as electric light bulbs followed not long after. China had it about two thousand years earlier, using bamboo pipes to convey natural gas supplies for heating and lighting, though I’m not sure how widespread that was. Probably, as with most things, it was more often found in the homes of the elite than the common masses.

But our approach to lighting hasn’t only been about finding things to burn. Remember the sun? We’ve often used structural solutions to maximize our use of its light. Lightwells are spaces within a building left open to the sky, bringing not just sun but much-needed fresh air to interior areas. It’s also common to carry out lots of daytime activities in rooms that face the south, which will get the most light throughout the day. If you can afford windows, supplying a room with many of them will make it brighter — though also harder to regulate in temperature, which we’ll look at in upcoming essays.

We even have ingenious tricks for getting light from where it is to where it’s needed. In antique stores you’ll sometimes see heavy glass prisms; these were set into the top decks of ships to refract light into the spaces below. Lightwells might have mirrors at the top, redirecting the sun into a narrow shaft that would otherwise receive little of it. Even dim, indirect light is better than none.

Tricks like those have the advantage of being something you install once and keep using. Torches, lamps, candles, gas, electricity — all of those are consumable things, meaning that if you want a room bright enough for activities like reading, sewing, or dancing, you’re going to have to pay for it. So the rich have more leeway to keep their own schedule, while the poor make do with the sun, or strain their eyes working by insufficient light.

I should note before we end that this isn’t just about lighting homes. Public lighting is also a thing, and many cities have taken steps to implement it for reasons of safety and crime reduction. Street lighting became much more widespread with the advent of gas, but even before that, there were public services hanging lanterns in the streets, or regulations requiring the residents of street-facing property to put out their own lanterns or light candles in their front windows, at least during certain hours. Where that’s absent or inadequate, you have servants or hired link-bearers carrying lanterns for their employers through the nighttime streets.

The downside to this, of course, is light pollution. I didn’t realize until I was nearly twenty how bright the full moon could be, because I’d rarely been far enough away from artificial lighting to notice its effect. When I look up at the sky and think I see a lot of stars, it’s the merest fraction of what’s actually up there. Unlike other forms of pollution, this one’s relatively easy to reverse, and some places are taking steps to implement dark-sky policies. In a world of ubiquitous light, it’s the smallest and most wondrous of them all that we must work to regain.