Definition of dusk and what is the difference between dusk and twilight?

Dusk:

What is dusk?

Dusk is the period in which darkness begins after the sun sets, or what is known as the beginning of the darkness of the night. Each of us notices carefully that after sunset the sky does not darken immediately, but rather darkness appears gradually during the period of time that is between the Maghrib call to prayer and the evening call to prayer. At the time of the Maghrib call to prayer, it is the time when the last visible point of the sun disappears behind the zero-altitude atmosphere, meaning that no mountain or plateau blocks the sun. You see that the sun is as it is and that it is dissolving on the horizon in a line exactly similar to the line of your feet on the zero-altitude earth.

Dusk and twilight and the difference between them

This is 100% noticeable on the seashore, as you can see the sun as if it were descending into the sea and sinking, as this is considered the time of sunset and the time for the Maghrib call to prayer, so another period passes after the Maghrib call to prayer, approximately 80 to 90 minutes, until it is complete. The complete darkness of the sky occurs after sunset. During this period, the sky continues to gradually enter into darkness until it reaches complete darkness about 90 minutes after sunset, and when darkness arrives, the time for the Isha call to prayer comes.

The light of dusk is an arc of the sun's rays. These rays are broad, white or pink in color, and are scattered in the sky in the form of particles such as dust that are suspended in the atmosphere. This light of dusk can appear above the furthest and highest cloud. At the time when dusk disappears or any reflection occurs in any region of the snow fields on the mountain after sunset.

Description of dusk:

What we can see at this time in the sky during these ninety minutes between the time of sunset and the time of dinner is what is called dusk, which consists of different colors of the utmost magnificence and beauty on the horizons of the sky from the direction of sunset. You can see multiple colors produced. About the phenomenon of refraction of solar rays at a distance greater in length from the atmosphere due to the intensity of the slope of the rays emerging from the sun with the plane of perpendicularity to the atmosphere immediately before and after sunset. The most beautiful color seen among these colors at dusk is the fiery red color. This color gives the sky a very beautiful appearance.

This period of dusk, which is characterized by its red color, is called the red twilight. As time passes, the darkness and darkness gradually increase, until when the time of dusk ends, intense darkness sets in, and dusk continues until the shadow of the Earth reaches the sky above the horizon. Darkness also sets in, the stars become clear, and the known planet Venus appears. The second luminous planet after the moon in the dark space above the horizon opposite Venus in the buffer zone from sunlight.

After the eruption of the Krakatoa volcano in 1883 AD, a red sunset appeared in a successive manner characterized by splendor and beauty around the world. Because of this abundant amount of volcanic dust caused by the eruption of the volcano, it reached a high altitude and reached, through atmospheric winds, many countries of the world.

The reason for dusk is that light does not come directly in the extreme darkness of daylight, the disappearance of sunlight in the upper places of the Earth's atmosphere.

What is the difference between dusk and twilight?

Dusk is the time that begins immediately after evening, and twilight is represented by the beginning of the morning when the sky is blue and bright. During dusk, it is necessary to have artificial light when reading outside because there is no sunlight to be scattered and illuminated. Unlike twilight, dusk is divided. It is divided into three main phases: civil, nautical, and astronomical dusk.

Stages of dusk occurrence:

Civil dusk occurs in the evening when the geometric center of the Sun is about 6 degrees below the horizon. Astronomical objects become visible at that time.

Marine dusk occurs in the evening when the sun is 12 degrees below the horizon. Stellar objects in the sky become clearly visible.

Sidereal dusk occurs when the Sun's geographic center is 18 degrees below the horizon. After this point, the sky was not as bright.

As for twilight, it is the time of day between sunrise and dawn, and the time between sunset and dusk. During twilight, the sun’s rays spread in the upper atmosphere and shine on the lower atmosphere of the Earth. It has been determined that twilight occurs during three sub-stages by astronomers, namely:

Civil, nautical, and space twilight depend on the ratio of the Sun's elevation relative to the Earth's horizon.

Civil twilight occurs when the sun falls below 6 degrees above Earth's horizon. It is the brightest aurora and the horizon is clearly visible without the aid of artificial light. States use the definition of civil twilight to enact laws regarding hunting, flying, and the use of headlights.

Nautical twilight occurs when the sun lies between 6 and 12 degrees below the horizon. During nautical twilight, artificial light is required for outdoor activities because there is little sunlight illuminating Earth's atmosphere. Marine twilight dates back to ancient times when sailors used the stars to navigate the sea. This phenomenon is used by the US Army to launch their tactical operations.

Astronomical twilight is the time when the Sun lies between 12 and 18 degrees below Earth's horizon. It is the darkest twilight when the sky is dark enough for all types of astronomical observations.

The length of the aurora depends on the latitude with the tropics and the tropics having shorter aurora compared to higher latitudes. During the polar regions during the March equinox, the North Pole does not experience nautical and astronomical aurora. Instead, there is a constant civil twilight. During the September equinox, there is no twilight at all in the Arctic due to the polar day and midnight morning. After this phenomenon, the sun sinks below the horizon causing days of continuous civil twilight and then subsequent days of nautical twilight followed by astronomical twilight. The same phenomenon exists in Antarctica at opposite times of the year.