What is Twilight, Dawn and Dusk?
Twilight is the time between darkness and sunrise in the morning, and sunset and complete darkness in the evening, when there is light outside, but the Sun is below the horizon. There are 3 types of twilight: civil, nautical, and astronomical.
Twilight time in your city
In the morning, twilight ends with dawn, while twilight in the evening ends with dusk. A number of atmospheric phenomena and colors can be seen during twilight.
Reflecting Sunlight
Twilight occurs when the Earth's upper atmosphere scatters and reflects sunlight and illuminates the lower atmosphere.
Astronomers define twilight in the context of the Sun's elevation with respect to the horizon (the angle that the geometric center of the Sun makes with the horizon). They also distinguish between 3 types of twilight, dawn and dusk based on this definition.
Civil Twilight, Dawn and Dusk
Civil twilight occurs when the Sun is between 0 degrees and 6 degrees below the horizon. In the morning, civil twilight begins when the Sun is 6 degrees below the horizon and ends at sunrise. In the evening, it begins at sunset and ends when the Sun reaches 6 degrees below the horizon.
Civil dawn begins when the geometric center of the Sun is 6 degrees below the horizon and ends with sunrise, which is the moment when the Sun's upper edge touches the horizon.
Similarly, civil dusk begins with sunset and ends when the geometrical center of the Sun goes 6 degrees below the horizon. Sunset is the instant when the trailing edge of the Sun goes below the horizon.
Civil twilight is the brightest form of twilight. There is enough natural sunlight during this period that artificial light may not be required to carry out human activities. Only the brightest celestial and space objects can be observed from Earth during civil twilight.
Several countries use this definition of civil twilight and civil dawn to make laws related to aviation, hunting, and the usage of headlights and street lamps.
In the United Kingdom, the time when everyone has to switch on their headlights is known as hours of darkness, which is 30 minutes before sunrise and after sunset.
