Dawn

Dawn is the period of morning twilight that occurs before the sun rises above the horizon. It marks the transition from the darkness of night to the light of day. This phenomenon happens because of indirect sunlight scattering through the Earth's atmosphere. This scattering becomes visible to an observer when the center of the Sun's disc reaches 18 degrees below the horizon.

This period of morning twilight continues until the moment of sunrise. Sunrise is defined as the point when the Sun's upper limb breaks the horizon. At that moment, direct sunlight becomes strong enough to outshine the diffused, scattered light of twilight. The word "dawn" itself comes from an Old English verb meaning "to become day."

Scientists categorize the morning twilight into three distinct stages based on the Sun's position. These stages are determined by the angular distance of the Sun's center below the horizon. The first stage is astronomical dawn, which begins when the Sun is 18 degrees below the horizon. During astronomical twilight, a small portion of the Sun's rays illuminates the sky. This causes the faintest stars to begin disappearing from view.

In many areas, astronomical dawn is difficult to distinguish from the night, especially if there is light pollution.

The second stage is known as nautical dawn. This begins when the center of the Sun reaches 12 degrees below the horizon. During nautical twilight, there is enough light for sailors to distinguish the horizon line at sea. However, the sky remains too dark for most other outdoor activities to be performed. The third and final stage is civil dawn. This occurs when the Sun is only 6 degrees below the horizon.

At civil dawn, most objects become distinguishable, allowing people to begin outdoor tasks. The sky often appears blue during this time, though clouds or haze can create bronze, orange, or yellow colors.

The duration of the twilight period is not the same everywhere on Earth. It varies significantly depending on the observer's latitude. At the Equator, the period of twilight is at its shortest. During the equinox at the Equator, the Sun rises due east and sets due west at a right angle to the horizon. In this specific location, each stage of twilight—astronomical, nautical, and civil—lasts only 24 minutes.

This results in a total twilight period of just over 70 minutes before sunrise.

In the polar regions, the timing of dawn changes drastically. As the summer solstice approaches, daytime becomes longer, and nighttime grows longer as the winter solstice approaches. At the polar circle, the Sun does not set at all during the summer solstice. This creates a very long period of twilight. In latitudes higher than 60°34′, summer nights may never get darker than civil twilight.

Near the summer solstice, latitudes above 54°34′ may not get darker than nautical twilight. For example, in cities like Oslo, Norway, or Stockholm, Sweden, the sky can seem very bright even while the Sun is below the horizon.

Dawn holds deep significance in many religious and mythological traditions. In Islam, astronomical dawn is called "True Dawn," while the Zodiacal Light is referred to as "False Dawn." The True Dawn marks the time for the first daily prayer and the start of the fast during Ramadan. In Hindu traditions, Ushas is the goddess of the dawn. There is also a specific time called brahmamuhurta, which is considered an ideal time for meditation and yoga.

In the Bible, Jesus is often symbolized by the morning dawn.

Different cultures have also developed unique ways to calculate the exact start of dawn. In Judaism, the Talmud discusses how to determine this time for religious laws. One reading suggests dawn occurs 72 minutes before sunrise. Another view, held by the Vilna Gaon, suggests dawn begins when the Sun is 16.1 degrees below the horizon. This difference is based on whether the timeframe refers to an equinox day in Mesopotamia. These various interpretations show how the transition from night to day affects human law, art, and spirituality across the globe.