Polar night

Based on Wikipedia: Polar night

Imagine looking at your watch at noon and seeing only stars. Not dusk, not twilight, but actual night—complete with the faintest stars visible to the naked eye scattered across a black sky. This happens every winter at the Amundsen-Scott research station in Antarctica, where the sun doesn't just set for a few hours. It disappears for nearly three months.

This is true polar night, the most extreme version of a phenomenon that affects millions of people living in Earth's northernmost and southernmost regions every year.

What Creates a Polar Night

Earth doesn't spin upright. Our planet tilts about 23.5 degrees on its axis, like a top that's slightly off-kilter. This tilt is why we have seasons at all—as Earth orbits the sun, different hemispheres lean toward or away from our star.

At middle latitudes, this creates longer summer days and shorter winter ones. But near the poles, the tilt produces something more dramatic. When your hemisphere leans away from the sun, you're not just getting less daylight. You're on a part of Earth that literally cannot see the sun at all. The planet itself blocks your view.

Think of it like standing on the dark side of a basketball. No matter how you crane your neck, you cannot see the lamp on the other side. You'd have to walk around to the lit half. For people in the polar regions during winter, that "walk" takes months—the slow orbital motion of Earth around the sun.

The boundary where this phenomenon begins is called the polar circle, located at approximately 66.5 degrees latitude in both hemispheres. Step inside this line, and at some point during winter, you'll experience at least one full day without the sun rising. The closer you get to the pole, the longer this sunless period lasts.

Not All Darkness Is Equal

Here's where it gets interesting. When most people imagine polar night, they picture complete blackness—the kind of darkness you'd find in a deep cave. But that's only true in the most extreme locations.

The atmosphere bends light. This phenomenon, called refraction, means that even when the sun is technically below the horizon, some of its light still reaches you. It curves around Earth's edge, scattered and diffused through the air. This is why we experience twilight at all—that gradual transition from day to night that makes sunsets so beautiful.

Scientists define twilight in three stages, each corresponding to how far the sun has sunk below the horizon.

Civil twilight is the brightest. The sun is less than six degrees below the horizon. You can still read a book outdoors. Bright planets like Venus become visible, and the most prominent stars emerge. Most people would call this "dusk" or "dawn" in everyday language.

Nautical twilight pushes the sun between six and twelve degrees below the horizon. The name comes from its historical importance to sailors—during this period, the horizon is still visible enough to navigate by the stars, but the sky is dark enough to see those stars clearly. It's a useful window for taking celestial measurements.

Astronomical twilight extends from twelve to eighteen degrees below the horizon. At this depth, the sky is dark enough for professional astronomers to observe most celestial objects. But faint traces of sunlight still linger, scattered through the upper atmosphere.

Only when the sun sinks more than eighteen degrees below the horizon does true night begin. No refracted sunlight reaches you. The sky is as dark as it can get.

The Gradient of Winter Darkness

This gradient of twilight creates a fascinating spectrum of polar night experiences, depending on latitude.

Tromsø, Norway sits at about 69 degrees north, just a few degrees inside the Arctic Circle. During its polar night, which lasts from late November to mid-January, the town doesn't experience complete darkness. Instead, residents see what might be called "civil polar twilight." Around midday, the southern horizon glows with a deep blue light. It's not exactly daylight, but it's enough to see by—enough to navigate without a flashlight, enough to conduct most outdoor activities.

A typical winter day in such a town follows a strange pattern. You wake in darkness. As noon approaches, the sky transitions through astronomical twilight, nautical twilight, and finally civil twilight. For perhaps an hour or two, there's that eerie blue glow—the sun trying and failing to crest the horizon. Then the process reverses, and night returns.

But the street lamps might stay on all day. If it's overcast, the clouds block even that dim twilight glow, and the town can feel as dark at noon as it does at midnight.

Travel further north—to Longyearbyen, Svalbard, at about 78 degrees—and the situation intensifies. Here, from roughly November 11 to January 30, the sun never gets close enough to the horizon to provide even civil twilight. The town experiences nautical polar twilight instead. At midday, you can just barely make out the shapes of buildings against the snow. The horizon shows a faint glow, but it's too dim for normal activities. You need electric lights to function.

Push still further north, past 84 degrees latitude, and you finally reach the zone of true polar night. Here, even at solar noon—the moment when the sun reaches its highest point in its below-horizon arc—it remains more than eighteen degrees below the horizon. Stars of the sixth magnitude, the faintest visible to the naked eye, shine all day long. The only settlements at these extreme latitudes are research stations.

The Asymmetry of Polar Days and Nights

There's a curious asymmetry in how Earth experiences these phenomena. You might expect polar day and polar night to be mirror images of each other—equal and opposite, balanced across the seasons. But they're not.

Because the atmosphere refracts sunlight, the sun remains visible even when it's geometrically below the horizon. This extends polar day and shrinks polar night. The area that experiences midnight sun is actually larger than the area that experiences polar night.

There's another asymmetry too. Earth's orbit around the sun is not a perfect circle but an ellipse. We move faster when we're closer to the sun, slower when we're farther away. This means the polar night at the North Pole lasts about 179 days, while the polar night at the South Pole stretches to approximately 186 days—a full week longer.

When it's polar night in the Arctic, it's polar day in the Antarctic, and vice versa. The two poles exist in perpetual opposition, never sharing the same lighting conditions.

Living Without the Sun

What happens to people who live through months of darkness? The research is fascinating—and somewhat contradictory.

A study in Tromsø examined sleep patterns among residents during the polar night. Surprisingly, people's total sleep duration remained relatively stable throughout the year. The extreme changes in daylight didn't dramatically alter how long people slept. However, men showed a higher prevalence of insomnia during the fall and winter months, suggesting that the quality of sleep may suffer even when its quantity doesn't.

The researchers speculated that Tromsø's abundant artificial lighting might explain the lack of dramatic sleep changes. Modern electric light creates a kind of artificial day, buffering residents against the extremes of their latitude.

Studies from Antarctic research stations paint a different picture. At Belgrano II, an Argentine station at 77 degrees south, researchers found that men actually slept longer in summer than winter—the opposite of what you might expect if darkness promoted sleep. The study also observed greater social jetlag during winter months, meaning people's internal clocks drifted further from the station's official schedule.

Most concerning, research at Korean Antarctic stations found that seven of 88 crew members developed mental health conditions during their first winter. These included insomnia disorder, depression, adjustment disorder, and alcohol use disorder. None of these individuals had prior mental health diagnoses.

The polar night takes a psychological toll.

Seasonal Affective Disorder and the Limits of Twilight

For people with seasonal affective disorder—a form of depression linked to reduced sunlight—the polar regions present a particular challenge. Treatment typically involves exposure to very bright artificial light, around 10,000 lux. To put that in perspective, a brightly lit office might provide 500 lux. Outdoor shade on a sunny day offers about 20,000 lux.

Even civil twilight—the brightest form of polar twilight—doesn't come close to 10,000 lux. For therapeutic purposes, any stage of twilight is still "polar night." The midday glow might be enough to read by, but it's nowhere near enough to reset the brain chemistry that can trigger depression.

This is why light therapy lamps are particularly important in polar regions. They're not just combating darkness—they're replacing a specific biological signal that the winter sun cannot provide.

A Universal Phenomenon

Earth is not unique in experiencing polar night. Any planet or moon with a sufficient axial tilt will have the same phenomenon, as long as it rotates on its axis much faster than it orbits its star.

Think about what that means. On some distant world, beings might experience polar nights lasting for years of their time. Or polar nights so brief they're barely noticeable. The specific character of any planet's polar night depends on the interplay between its tilt, its rotation speed, and its orbital period.

Our own polar night is defined by Earth's 23.5-degree tilt, our 24-hour rotation, and our 365-day year. These numbers create the particular rhythm of darkness that residents of Tromsø, Longyearbyen, and Antarctica know so well.

The Return of the Sun

In polar communities, the end of polar night is often celebrated with festivals and traditions. The first glimpse of the sun after weeks or months of darkness is an event of genuine significance.

In some Svalbard communities, residents gather at elevated points to catch the first rays—the sun appears above the horizon for just a few minutes before slipping away again, but those minutes feel miraculous. In the days that follow, the sun rises higher and stays longer, and the long climb back toward summer begins.

For those who have never experienced it, the polar night is difficult to imagine. It's not just darkness. It's a fundamental reordering of your relationship with time and light. Clocks and artificial illumination replace the natural rhythm of day and night. Your body must adjust to cues that are entirely human-made.

And yet millions of people do live this way, every year, and have for thousands of years. The Sámi people of northern Scandinavia, the Inuit of Arctic Canada and Greenland, and countless other indigenous peoples developed cultures deeply adapted to the polar night. They learned to navigate by starlight, to find meaning in the aurora borealis, to structure their lives around rhythms that most of humanity never experiences.

The polar night is not just a meteorological phenomenon. It's a different way of being human.