What Is the Difference between Dusk and Twilight?

G. Wiesen

In order to understand the difference between dusk and twilight, it is important to understand a few important terms with regard to the observed movement of the sun in relation to the earth. There are four terms that are interrelated and help clarify the meaning of “twilight.” Dawn is the moment at which the sun’s light begins to illuminate an area though the sun is not visible, and sunrise is the point at which the sun becomes visible; sunset is the moment when the sun is no longer visible, and dusk is the point at which an area becomes dark. Twilight is the time between dawn and sunrise and between sunset and dusk, during which light is scattered indirectly from the sun to illuminate an area.

Sunset is the point when the sun is no longer visible on the horizon.
Sunset is the point when the sun is no longer visible on the horizon.

Dusk and twilight are different concepts, though they are closely related with regard to how the sun appears to move throughout the sky. Even though twilight is commonly associated with sunset and dusk, it actually occurs twice each day. In the morning, dawn is the moment in which the sun begins to illuminate the sky and twilight is the period when sunlight is scattered by the atmosphere to provide indirect lighting. This is followed by sunrise, when the sun becomes visible over the horizon in the morning.

Twilight describes both the period between dark and dawn and the period between sunset and dark.
Twilight describes both the period between dark and dawn and the period between sunset and dark.

At the end of the day is a similar process, played out in reverse, in which both dusk and twilight occur. Sunset is the moment when the sun is no longer visible over the horizon, which begins a period of twilight in the evening when indirect lighting is created again by sunlight scattered by the atmosphere. This twilight technically ends at dusk, when this light is replaced by darkness. The basic difference between the two is, therefore, that twilight is a period in which evening light is still provided indirectly by the sun, while dusk is when this light has faded for the night.

Timing for both dusk and twilight can be affected by a number of factors. The position of an observer on the earth, with regard to his or her latitude, can have a direct impact on when dusk and twilight occur for him or her. Seasonal changes based on the tilt of the earth can alter the duration of twilight in the morning and evening. There are also three different types of twilight, based on the position of the sun: civil twilight occurs when the sun is not visible but its center is below the horizon less than 6°; nautical twilight is observed when sun's center is 6° to 12° below the horizon; and astronomical twilight happens as the sun is 12° to 18° below the horizon.

A mountain at sunrise.
A mountain at sunrise.

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Discussion Comments


Sunset, twilight and dusk are my favorite times of the day. I love the different hues that show up in the sky during this time, especially when the sun is setting. I also love how the sky looks at twilight, it lives up to its name. I think twilight means "dimmed light" and that's really how the sky looks at this time.


@fify-- Yea, most people think that there is an exact time when twilight occurs, but it really varies depending on where the person is location wise.

The meaning of dusk is straightforward, it's the time when the sky becomes completely dark. Twilight is a little confusing. It's the time in between the sky becoming lighter and the sun being spotted, and the sun disappearing and the sky becoming dark. If one remembers it this way, then it becomes less confusing.


It's natural for people to get confused about this because there are so many different terms used for the way the sky looks as the sun rises and sets. It also doesn't help that twilight actually refers to two different times of the day.

I, for example, always thought that twilight was something that occurs right before it becomes night. You know the time when it's not bright, but it's not quite dark yet either. One can easily walk around outside at this time without needing a light source. But I was not aware that twilight refers to the time before the sun rises as well.

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