dawn

Dawn is the period in the morning when light first appears as the Sun rises toward the horizon, before the Sun itself is visible. It is the pre-dawn twilight that precedes sunrise. The exact appearance of dawn depends on latitude, season, atmospheric conditions, and terrain.

During dawn, the sky passes through distinct phases used by navigators and astronomers: astronomical dawn, nautical dawn, and civil dawn. Astronomical dawn occurs when the Sun is 18 degrees below the horizon; the sky begins to brighten but most stars remain visible. Nautical dawn occurs when the Sun is 12 degrees below; the horizon becomes discernible and marine navigation is feasible. Civil dawn occurs when the Sun is 6 degrees below; there is enough light for most outdoor activities, and civil twilight ends at sunrise. Sunrise is when the upper limb of the Sun crosses the horizon.

Cultural aspects: Dawn has been a common symbol of renewal and beginnings in many cultures; personifications include the Greek Eos and the Roman Aurora; the term “dawn” is used metaphorically in phrases such as “dawn of a new era.” The dawn chorus—early morning birdsong as light increases—is a well-known natural phenomenon associated with this time.

In science and technology, “Dawn” also names a NASA space probe launched in 2007 to study the asteroid belt, visiting Vesta and Ceres from 2011 to 2015.