Sunrise and sunset

Sunrise and sunset: how does it work exactly?

Sunrise is the moment when the sun becomes visible above the horizon. Sunset is the moment when the sun disappears completely below the horizon again. For many people, these moments feel like the natural beginning and end of the day, but astronomically there is much more to it.

On this page you can read how sunrise and sunset occur, why the times differ by place and why in some parts of the world it can stay light or dark for weeks on end.

Why does the sun rise and set?

The sun appears to rise in the east and set in the west every day. In reality, the sun does not move around the Earth; the Earth rotates on its own axis. Because of that rotation, a different part of the Earth is illuminated by the sun each time.

When your location turns towards the sun, it becomes morning and the sun appears above the horizon. When your location turns away from the sun, it becomes evening and the sun disappears below the horizon.

Because the Earth makes one full rotation in roughly 24 hours, we experience an alternation of day and night every day.

Why do sunrise and sunset differ by place?

The times of sunrise and sunset are not the same everywhere. They depend on several factors:

• location on Earth;
• time zone;
• season;
• height of the horizon;
• distance from the equator;
• date in the year.

A place in the east of a country usually sees the sun rise earlier than a place in the west. It also matters a great deal whether you live close to the equator or far to the north or south.

In the Netherlands and Belgium, days are long in summer and short in winter. Around June the sun rises early and sets late. Around December it is the opposite: the sun rises late and disappears behind the horizon early.

Why is it already light before sunrise?

It is often already light before the sun itself is visible. That is due to morning twilight. During twilight the sun is still below the horizon, but its light is already scattered in the atmosphere.

As a result, the sky can already become lighter while the sun has not officially risen yet. The same happens after sunset. It then stays light for a while because sunlight is spread through the atmosphere.

There is therefore a difference between:

• sunrise: the moment when the sun becomes visible above the horizon;
• daylight: the period when it is light enough outside to see well;
• twilight: the transition between night and day or between day and night.

Why can you sometimes see the sun while it is still below the horizon?

A remarkable phenomenon at sunrise and sunset is atmospheric refraction. The Earth's atmosphere bends sunlight slightly. As a result, the sun appears to stand a little higher than it actually does.

That means we can already see the sun at sunrise while astronomically it is still just below the horizon. At sunset the opposite happens: we continue to see the sun for a brief moment while it has actually already disappeared below the horizon.

Why does the sky turn red, orange or pink?

When the sun is low, the sky often takes on beautiful colours. Think of red, orange, pink or golden light. This happens because sunlight travels a longer path through the atmosphere when the sun is low on the horizon.

During the day, when the sun is high, mainly blue light is scattered. That is why we usually see a blue sky. At sunrise and sunset, sunlight must pass through a much thicker layer of air, dust particles and moisture. Other colours then become more visible, especially red and orange.

A sunset is often more intense in colour than a sunrise. That is because at the end of the day there is usually more dust, moisture and small particles in the air.

What is the difference between morning twilight and evening twilight?

Morning twilight is the period between the first light in the sky and official sunrise. This period is also called dawn.

Evening twilight begins after sunset. The sun has then already disappeared, but it is not immediately dark. The sky remains lit for a while because sunlight is spread through the atmosphere.

There are different types of twilight:

• Civil twilight — It is still fairly light outside. You can usually walk around outside without artificial light.
• Nautical twilight — The horizon is still visible, but it is clearly getting darker. This phase was historically important for navigation.
• Astronomical twilight — The sun is so far below the horizon that the sky is almost completely dark. This is important for stargazing and astronomy.

Why are days longer in summer than in winter?

The length of the day changes because of the Earth's tilt. The Earth does not stand upright relative to its orbit around the sun, but leans slightly. As a result, the northern hemisphere receives more sunlight in summer and less in winter.

In the Netherlands and Belgium this means:

• in June the days are longest;
• in December the days are shortest;
• around March and September day and night are roughly equal in length.

The longest day of the year in the northern hemisphere usually falls around 21 June. The shortest day usually falls around 21 December.

What is the midnight sun?

In areas around the North Pole and South Pole, the sun may not set at all during certain periods. This phenomenon is called the midnight sun.

During the midnight sun, the sun remains above the horizon 24 hours a day. It therefore does not become truly dark. This happens, for example, in parts of Norway, Sweden, Finland, Iceland, Greenland, Canada, Alaska and Russia.

The further north you go, the longer this period lasts. In some places it stays light for weeks or even months in a row.

What is polar night?

The opposite of the midnight sun is polar night. During polar night, the sun does not rise above the horizon for a certain period.

That does not always mean it is pitch dark 24 hours a day. There is often still twilight, especially at the edges of the polar region. But the sun itself remains below the horizon.

Polar night occurs in areas around the North Pole and South Pole. In the Arctic it happens during our winter. In the Antarctic it happens during our summer.

Where does it sometimes stay light all day?

In areas above the Arctic Circle, it can stay light 24 hours a day in summer. Well-known places where you can experience the midnight sun include:

• Northern Norway;
• Lapland;
• Svalbard;
• Iceland to a limited extent;
• Greenland;
• Northern Canada;
• Alaska.

For travellers this is a remarkable natural phenomenon. You can still walk, photograph or do activities outdoors in the middle of the night without it becoming dark.

Where does it sometimes stay dark all day?

In winter, the opposite can happen in the same polar regions: the sun does not rise. This occurs in places far above the Arctic Circle, such as parts of Northern Norway, Svalbard, Greenland, Alaska and Northern Canada.

This phenomenon also occurs in Antarctica. The seasons there are reversed compared with Europe. When it is summer here, it is winter there.

Why do sunrise and sunset not change equally strongly everywhere?

Close to the equator, days and nights are almost the same length almost all year round. The sun often rises and sets at roughly the same time there.

Further from the equator, the differences become much greater. In the Netherlands and Belgium we notice this clearly: long summer evenings and short winter days. In Scandinavia the differences are even more extreme. There it can barely get dark in summer and in winter there may be only a few hours of light.

Facts about sunrise and sunset

The sun does not rise exactly in the east everywhere. Only around the times when day and night are roughly equal does the sun rise almost exactly in the east and set almost exactly in the west.

The colours at sunrise and sunset are influenced by dust, moisture, clouds and air pollution. That is why one sunset can be much more spectacular than another.

A red morning sky is often seen in old weather sayings as a sign of approaching bad weather. A well-known saying is: "Red sky at morning, sailors take warning."

The expression "The early bird catches the worm" refers to the idea that getting up early has advantages and that morning is a valuable part of the day.

On the moon you would not see a colourful sunrise as on Earth. That is because the moon has virtually no atmosphere. Without an atmosphere there is hardly any scattering of sunlight.

Symbolic meaning of sunrise

Sunrise is often seen as a symbol of a new beginning. A new day, new opportunities, hope and progress are often associated with the rising sun.

Sunrise also appears regularly in flags, art, religion, literature and music. Japan, for example, is known as the land of the rising sun. The red sun is a well-known symbol strongly associated with Japan.

Sunset often has a different symbolic meaning. It is more often associated with rest, closure, romance, reflection or the end of a period.

Looking up sunrise and sunset times

The exact times of sunrise and sunset differ by place and date. It is therefore useful to look up these times per location.

On CurrentLocalTime.com you can see per place what time the sun rises and sets today. That way you see not only the current local time, but also how much daylight remains, when it gets dark and how the day unfolds at your chosen location — including a timeline of the past 5 and coming 20 days.

Summary

Sunrise and sunset occur because the Earth rotates on its own axis. The exact times differ by place, season and date. Because of the atmosphere it is often already light before the sun is visible and it remains twilight for a while after sunset.

Special phenomena such as the midnight sun and polar night show how great the differences on Earth can be. In some places it stays light for weeks in summer, while in winter the sun does not rise for a long time.

Sunrise and sunset are therefore not only practical times, but also impressive natural phenomena that are experienced differently all over the world.