Polar night

At the top and bottom of Earth, the sun stays down.

This is called the polar night. It can last for a very long time. At the poles, it lasts for many days.

It is not always pitch black. The sky can still have some light. This light comes from the sun being just below the ground. You might even see bright stars in the sky.

Some places stay light for a long time. It is a very special time of year.

At the top and bottom of Earth, the Sun stays below the horizon.

This is called the polar night. It only happens inside the polar circles. This means the Sun does not rise for more than 24 hours.

It is not always pitch black outside. The sky often has different kinds of twilight. Twilight is the soft light seen when the Sun is just below the horizon.

There are three main kinds of twilight. Civil twilight is the brightest. You can still do most outdoor tasks in this light. Nautical twilight is darker. You can see the shapes of things, but not small details. Astronomical twilight is the darkest. The sky is dark enough to see stars.

At the very poles, there is true polar night.

This is a time of non-stop darkness. Even the dimmest stars stay visible all day. The polar night lasts for different amounts of time. At the North Pole, it lasts about 179 days. At the South Pole, it lasts about 186 days.

Have you ever wondered what happens when the Sun never rises? This special event is called the polar night. It happens in the northernmost and southernmost parts of Earth. These areas are located inside the polar circles. During this time, the Sun stays below the horizon for more than 24 hours.

This is the opposite of the midnight sun. The midnight sun is when the Sun stays above the horizon for a long time. The polar night is a fascinating way to see how our planet moves.

Even when the Sun is below the horizon, it is not always pitch black. The sky often has different levels of light called twilight. This happens because the atmosphere bends sunlight over the horizon. This bending is called refraction.

First, there is civil twilight. This is the brightest stage, and you can do most outdoor activities. Next is nautical twilight. During this stage, you can see the outlines of objects. Finally, there is astronomical twilight. This is the darkest stage, where the sky is dark enough to see stars.

Scientists use different measurements to define these stages of light. Civil twilight occurs when the Sun is between 0 and 6 degrees below the horizon. Nautical twilight happens when the Sun is between 6 and 12 degrees below. Astronomical twilight occurs when the Sun is between 12 and 18 degrees below. Beyond 18 degrees, the sunlight is no longer visible. This final stage is called true polar night. At this point, the sky is dark enough to see the dimmest stars all day long.

Many places on Earth experience these different types of polar nights. The town of Longyearbyen in Svalbard sees nautical twilight from November to January. In Canada, the place called Alert sees astronomical polar night from November to January.

The North Pole experiences polar night from November 12 to January 28. The South Pole has a different schedule. It experiences polar night from May 11 to August 1. At the very poles, the darkness can last for many weeks. The length of the night changes depending on how far north or south you are.

These patterns happen because of how the Earth tilts and moves. The Earth's orbit is an ellipse, which is a shape like a stretched circle. Because of this shape, the polar night is not the same length at both poles. The North Pole has about 179 days of polar night. The South Pole has about 186 days of polar night.

This shows us how much the Earth's path affects our world. It is a beautiful example of how space and Earth work together.

The polar night is a natural phenomenon occurring in the Earth's northernmost and southernmost regions. It happens when the Sun remains below the horizon for more than 24 consecutive hours. This event only occurs within the polar circles, located at latitudes of approximately 66.5 degrees. The opposite event is known as the polar day, or the midnight sun, where the Sun stays above the horizon for over 24 hours. Because the Earth's atmosphere refracts, or bends, sunlight, the polar day actually lasts longer than the polar night. Consequently, the area experiencing polar day is slightly larger than the area experiencing polar night.

Even when the Sun is below the horizon, the sky is not always completely dark. This is due to different stages of twilight, which is the gradual transition between light and dark. Civil twilight occurs when the Sun is between 0 and 6 degrees below the horizon. During this phase, nearby planets like Venus and bright stars like Sirius are visible. Nautical twilight follows, lasting until the Sun reaches 12 degrees below the horizon. In this stage, the horizon is still visible enough for navigation. Finally, astronomical twilight continues until the Sun sinks 18 degrees below the horizon. Beyond this 18-degree mark, refracted sunlight is no longer visible, resulting in true night.

Polar night is categorized into specific types based on the level of light present at solar noon. Civil polar twilight occurs at latitudes between roughly 67° 24' and 72° 34'. During this time, there is no true daylight, but light scattering by the upper atmosphere allows for most normal outdoor activities. However, dense cloud cover can make these days much darker. In these conditions, street lamps might stay on even at midday. This level of light is often insufficient for people with seasonal affective disorder, who may require higher levels of ambient light, such as 10,000 lux, for psychological benefits.

As one moves further toward the poles, the light levels decrease. Nautical polar twilight happens between latitudes of 72° 34' and 78° 34'. At this stage, the human eye can see the general outlines of ground objects at midday, but detailed outdoor operations are difficult. An example is the Norwegian town of Longyearbyen in Svalbard, which experiences this from about November 11 until January 30. Another example is Pond Inlet in Nunavut, Canada, where it lasts from December 16 to December 26.

Astronomical polar twilight occurs even closer to the poles, between latitudes 78° 34' and 84° 34'. During this period, the sky is dark enough at midday to permit the observation of stars. However, observing faint objects like nebulae or galaxies may still be difficult. The Canadian research base of Eureka, Nunavut, experiences this from early December to early January. Alert, the northernmost settlement in the world, experiences astronomical polar night from November 19 to January 22.

True polar night is the most extreme stage, occurring at latitudes above approximately 84° 34'. During this time, no astronomical twilight occurs at the solar culmination. The Sun remains between 18 and approximately 23° 26' below the horizon at noon. In these conditions, the dimmest stars visible to the naked eye, known as sixth-magnitude stars, can be seen throughout the entire 24-hour day. At the poles themselves, these conditions can last for about 11 weeks. The South Pole experiences true polar night from about May 11 to August 1, while the North Pole experiences it from November 12 to January 28.

The duration of the polar night varies significantly depending on your latitude. At the edge of the polar circle, the night may last only 24 hours, but at the poles, it can last about half a year. Interestingly, the length of the polar night is not the same in both hemispheres. This asymmetry is caused by the Earth's elliptical orbit and the laws of planetary motion. Because of this, the North Pole experiences about 179 days of polar night, while the South Pole experiences about 186 days.

This phenomenon is not unique to Earth. Any planet or moon with a sufficient axial tilt can experience a polar night. For this to happen, the body must rotate with respect to its star more frequently than it orbits the star. Additionally, there must be no tidal locking between the planet and its star. This means the same side of the planet does not always face the star, allowing for the cycle of light and darkness that creates these long nights.