A twilight hour refers to the time of day when it is not quite daylight but also not yet completely dark outside. It is the period when the sun is below the horizon but its light still illuminates the sky. Twilight hours occur in the mornings before sunrise and in the evenings after sunset. The amount of daylight during twilight hours depends on the time of year and your location on the planet.
Morning Twilight
In the morning, twilight begins when the geometric center of the sun is 18 degrees below the horizon and ends at sunrise. During this time, the brightest stars and planets remain visible but some light from the sun starts to brighten the sky. The dimmest stars disappear from view as the sky gets brighter. Morning twilight provides enough light for most outdoor activities without artificial lighting. However, details remain difficult to see and colors are muted.
Morning twilight can be divided into three phases:
- Civil twilight – When the sun is less than 6 degrees below the horizon. There is enough light for most outdoor activities to be done without artificial lighting.
- Nautical twilight – When the sun is between 6 and 12 degrees below the horizon. At this time, the brighter stars and planets are becoming visible but ambient light limits detailed outdoor visibility.
- Astronomical twilight – When the sun is between 12 and 18 degrees below the horizon. At this time the sky is dark enough for most astronomical observations.
The duration of morning twilight depends on your latitude and the time of year. At the equator, morning twilight lasts only about 25 minutes. But at higher latitudes, during summer months, morning twilight can last for several hours.
Evening Twilight
In the evening, twilight starts when the sun dips to 18 degrees below the horizon and continues until sunset when the sun reaches 0 degrees. As with morning twilight, there are also three distinct phases:
- Astronomical twilight – When the sun is between 18 and 12 degrees below the horizon. Outdoor conditions are dark enough at this time for most astronomical observations.
- Nautical twilight – When the sun is between 12 and 6 degrees below the horizon. The brighter planets and stars are visible but there is still some ambient light in the sky.
- Civil twilight – When the sun is less than 6 degrees below the horizon. Natural light is still sufficient for most activities but artificial lighting becomes necessary for detailed or complex tasks.
Evening twilight, like morning twilight, is longer at higher latitudes. At the equator it may last only half an hour after sunset but at higher latitudes during summer, it can linger for hours into the night.
Reasons for Twilight
Twilight occurs because of the refraction and scattering of sunlight through the Earth’s atmosphere. As the sun’s rays enter the atmosphere at sunrise and sunset they must pass through more air mass resulting in increased scattering and dispersion of light. In addition, the curvature of the Earth causes the sun’s rays to continue illuminating the atmosphere even when the sun is geometrically below the horizon.
The main factors that affect the duration and brightness of twilight are:
- Latitude – Twilight lasts longer at higher latitudes further from the equator.
- Time of year – Twilight is longer around summer solstice and shorter around winter solstice.
- Atmospheric conditions – More dust or humidity in the air can extend twilight times.
- Local terrain – The presence of mountains and valleys alters sunlight angles.
Civil, Nautical & Astronomical Twilight
The civil, nautical and astronomical definitions provide standardizations for measuring the amount of light available during twilight periods. Here are some details on each phase:
Civil Twilight
- Sun is less than 6 degrees below the horizon
- Enough natural light for most outdoor activities
- Artificial lighting may be required for detailed tasks
- Lasts 15-30 minutes at the equator, up to several hours at high latitudes
Nautical Twilight
- Sun is between 6 and 12 degrees below the horizon
- Outdoor light becomes noticeably dimmer
- Brighter stars and planets visible
- Horizon still discernible
- Lasts 30-60 minutes at the equator, up to several hours at high latitudes
Astronomical Twilight
- Sun is between 12 and 18 degrees below the horizon
- Skies are dark enough for most astronomical observations
- Fainter stars visible
- Horizon barely distinguishable
- Lasts 60+ minutes at the equator, may extend for entire night at high latitudes
Importance for Navigation
Historically, twilight hours were important for navigation, particularly nautical twilight. Before modern navigation instruments, determining a ship’s position relied on accurate measurements of stars and planets. Nautical twilight provided just enough light in the sky for these celestial objects to be identified while still being dark enough to clearly view and measure them.
The following table provides some examples of activities associated with each twilight phase:
| Twilight Phase | Light Conditions | Typical Activities |
|---|---|---|
| Civil Twilight | Enough natural light for most tasks | Commuting, fishing, farming, sports |
| Nautical Twilight | Dim but still enough light to discern horizon | Boating, navigation using stars |
| Astronomical Twilight | Quite dark but some vestiges of light | Astronomy, photography |
Modern ships and planes rely on radar, GPS and other technology for position measurements but the different twilight phases are still important for timing certain activities. Knowing lengths of morning and evening twilight continues to be crucial for farmers, construction companies, schools and many other fields that depend on the availability of sunlight.
Twilight Times Around the World
Lengths of twilight vary widely depending on location and time of year. Here are some examples of twilight durations in major cities around the world:
New York City
- June 21 (summer solstice) – Morning twilight starts around 3:40am and lasts over 2 hours until sunrise at 5:25am. Evening twilight lasts from about 8pm until around 9:45pm when astronomical twilight ends.
- December 21 (winter solstice) – Morning twilight is only about 45 minutes from 6:20am sunrise to 7:05am. Evening twilight is also shorter lasting from 4:30pm to 5:50pm sunset.
London
- June 21 – Morning twilight is from 2am to 4:43am sunrise. Evening twilight is from 9:16pm to 11:20pm.
- December 21 – Morning twilight 7:43am to 8:38am. Evening twilight 3:50pm to 5:15pm.
Tokyo
- June 21 – Morning twilight 3:26am to 4:28am sunrise. Evening 7:41pm to 8:54pm sunset.
- December 21 – Morning twilight 6:20am to 7:17am. Evening 4:31pm to 5:38pm.
Sydney
- June 21 – Morning twilight 5:02am to 7:22am sunrise. Evening 5:23pm to 6:42pm sunset.
- December 21 – Morning twilight 4:34am to 5:44am. Evening 7:03pm to 8:17pm.
Dubai
- June 21 – Morning twilight 4:17am to 5:36am sunrise. Evening 6:48pm to 7:53pm sunset.
- December 21 – Morning twilight 6:00am to 6:58am. Evening 5:13pm to 6:15pm.
Locations near the equator like Singapore and Quito have much less variation in twilight durations throughout the year. Higher latitude cities can have extreme differences between summer and winter morning/evening twilight times.
Twilight Colors
In addition to creating periods of soft lighting, twilight hours also produce beautiful colors in the sky. During evening twilight, the sky can display stunning yellows, oranges, reds, and purples. In the mornings, twilight skies are often dominated by pastel pinks, blues, and violets.
These twilight colors are created by the scattering of sunlight through the atmosphere. Shorter blue and violet wavelengths scatter more as sunlight passes obliquely through greater air mass. Meanwhile, longer orange and red wavelengths pass more directly through, creating the distinctive twilight glows.
Factors like atmospheric pollutants, cloud formations, humidity, and even volcanic ash can all contribute to more vivid and prolonged twilight colors. The colors are not seen every morning and evening but when conditions are right, twilight can provide an awe-inspiring start or end to your day.
Famous Depictions
The ethereal lighting and colors of twilight hours have inspired many famous artists, composers, and writers. Here are some examples of well-known twilight themed works:
- Paintings: “Twilight in the Wilderness” by Frederic Edwin Church, “Summertime Twilight” by Edward Hopper
- Classical Music: “Morning Mood” and “In the Hall of the Mountain King” by Edvard Grieg
- Ballet: “La Bayadère” (Kingdom of the Shades scene) choreographed by Marius Petipa
- Poetry: “Crossing Brooklyn Ferry” by Walt Whitman, “The Twilight Turns from Amethyst” by Christina Rossetti
- Literature: “Twilight” saga by Stephenie Meyer, “The Twilight Hour” by Elizabeth Wilson
Poets, composers, and artists are drawn to the serene glow and elusive nature of twilight. They capture its transient beauty and sense of change from day to night through expressive works in various mediums.
Twilight Around the World
While twilight happens globally, there are some variations in how it is described in different languages and cultures:
- Germany – “dämmerung” refers to both dawn and dusk twilight
- Spain – “crepusculo” is twilight, “atardecer” is dusk, “amanecer” is dawn
- Arabia – “shafaq” is twilight or the approaching darkness
- India – “sandhya” or “godhuli” refers to early evening twilight
- Japan – “tasogare” is dusk, “akatsuki” is dawn
Twilight is a universal phenomenon but is sometimes described differently based on local culture and language. Yet the tranquil beauty of morning and evening twilight is appreciated worldwide.
Conclusion
Twilight’s soft glow and colorful skies have captured the human imagination for millennia. The periods of dimming light in the mornings and evenings provided important transitions for ancient societies. While technology has reduced twilight’s navigational necessity, its beauty and symbolism endures.
Morning and evening twilights divide day from night all around the world. Their durations and colors change with location and season creating magical displays. Twilight’s dusks and dawns continue to inspire art, music, poetry and prose.
So next time you witness the magnificent transformation of sky from day to night or night to day, take a moment and appreciate the natural wonder of twilight.