Sunset facts for kids
Sunset, also known as sundown, is when the Sun disappears below the horizon each day. This happens because of Earth's rotation. If you are at the Equator, the sun sets exactly to the west during spring and autumn. If you are in the middle parts of the world, the summer sun sets towards the northwest in the Northern Hemisphere. In the Southern Hemisphere, it sets towards the southwest.
In astronomy, sunset is the exact moment the top edge of the Sun dips below the horizon. When the sun is near the horizon, Earth's atmosphere bends the sunlight. This makes the sun appear higher than it actually is. So, when you see the sun setting, it is already a little bit below the horizon.
Sunset is different from twilight. Twilight has three parts. The first part is civil twilight. This begins when the sun goes below the horizon and lasts until it is 6 degrees below. The second part is nautical twilight, which is when the sun is between 6 and 12 degrees below the horizon. The third part is astronomical twilight, when the sun is between 12 and 18 degrees below the horizon. Dusk is the very end of astronomical twilight. It is the darkest part of twilight, just before night begins. Night starts when the sun is 18 degrees below the horizon and no longer lights up the sky.
Places very far north, like the Arctic Circle, or very far south, like the Antarctic Circle, do not have a full sunset every day of the year. This happens during the polar day or the polar night, when it is light or dark for 24 hours straight.
Why do sunset times change?
The time of sunset changes throughout the year. It depends on where you are on Earth, including your longitude, latitude, and how high up you are. These daily changes happen because of Earth's tilt, its daily spin, and its yearly path around the Sun. The Moon's movement around Earth also plays a small part.
During winter and spring, the days get longer. Sunsets happen later each day. This continues until the day with the latest sunset, which is usually after the summer solstice. In the Northern Hemisphere, the latest sunset happens in late June or early July. This is not exactly on the summer solstice (June 21). The exact date depends on your location. It is also affected by Earth moving slower around the Sun in early July (this point is called aphelion).
Similarly, the earliest sunset does not happen on the winter solstice. It occurs about two weeks earlier. In the Northern Hemisphere, this is in early December or late November. This is because Earth moves faster around the Sun in early January (this point is called perihelion).
The same things happen in the Southern Hemisphere, but the dates are switched. The earliest sunsets are before June 21 in winter. The latest sunsets are after December 21 in summer. For a few weeks around the summer and winter solstices, both sunrise and sunset happen a little later each day. Even at the equator, sunrise and sunset times shift a few minutes throughout the year. These changes can be shown on a special diagram called an analemma.
When the sun sets, it usually appears in the northwest from March to September. From September to March, it appears in the southwest. On the spring and autumn equinoxes, the sun sets almost exactly to the west for everyone on Earth.
Daytime is slightly longer than nighttime. This is because sunrise and sunset are measured from the edges of the sun, not its center. Also, Earth's atmosphere bends sunlight. This means you can still see the sun even after it has gone below the horizon. This bending of light also makes the sun look a bit squashed when it is very close to the horizon. The bottom part of the sun's light bends more than the top. This makes the bottom edge appear higher, so the sun looks wider than it is tall. The sun also seems bigger when it is on the horizon, but this is just an optical illusion.
Places north of the Arctic Circle and south of the Antarctic Circle do not have a sunset or sunrise every day. This happens during the polar day or the polar night, when it is light or dark for 24 hours.
Why are sunsets colorful?
When white sunlight travels through the air to your eyes, some colors are scattered away by tiny air molecules and particles. This changes the color of the light you see.
Blue and green light have shorter wavelengths. They scatter more easily than other colors. So, these colors are mostly removed from the sunlight.
At sunrise and sunset, sunlight travels through more of the atmosphere. This means almost all the blue and green light is scattered away. This leaves the longer wavelength colors, like orange and red, for us to see. These red and orange colors can then be scattered by clouds and other particles. This makes the horizon look red and orange. This scattering of shorter wavelengths is called Rayleigh scattering. It happens because of air molecules and particles much smaller than the light's wavelength.
Scattering by larger particles, like cloud droplets, is called Mie scattering. This type of scattering does not depend much on the light's wavelength. Mie scattering is why clouds look white. It also causes the white glow around the sun during the day.
Sunset colors are usually brighter than sunrise colors. This is because the air in the evening often has more tiny particles than the morning air. Sometimes, just before sunrise or after sunset, you might even see a green flash.
Ash from volcanic eruptions can change sunset colors. If the ash is low in the atmosphere, it can make sunsets look dull. But if volcanic ash goes high into the stratosphere, it can create beautiful colors after sunset. These are called afterglows. Famous eruptions like Mount Pinatubo in 1991 and Krakatoa in 1883 caused amazing afterglows around the world. The high-altitude clouds reflect the reddened sunlight back down to Earth after the sun has set.
You can also see many different colors in the sky opposite the sun (the eastern sky) during twilight. These colors can be very varied and unusual, depending on the weather and the types of clouds.
Images for kids
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Evening twilight in Joshua Tree, California, USA showing orange colors near the sun and blue colors from the sky.
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Illuminated downdraft wind shear clouds in the eastern sky near dusk look like aurora borealis in the Mojave Desert.
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Sunset on Mars.
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Just after sunset, Woodlands, Singapore.
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Sunset in Brela, Croatia.
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Fiji.
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A red sunset near Swifts Creek, Australia.
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Minutes before sunset near Gulf of Paria, Trinidad and Tobago.
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Silhouettes of fishermen during a sunset in Payallar, Alanya.
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Sunset in Fernando de Noronha Archipelago, Brazil.
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Sunset view of the Paranal Observatory, with two comets in the southern skies.
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The very beginning of sunset over the Mojave Desert during extreme haze from California fires in 2016.
See also
In Spanish: Ocaso para niños
