Twilight Time

Here’s another song for your enjoyment. It was originally done by The Three Suns in 1944 and made popular by Les Brown and His Band of Renown in 1945 as an instrumental on the B-side of “Sentimental Journey” with vocals by Doris Day. Most boomers, though, know it from the version by the Platters in 1958.

Heavenly shades of night are falling
It’s twilight time
Out of the mist your voice is calling
It’s twilight time
When purple colored curtains
Mark the end of the day
I hear you my dear at twilight time

I was thinking about “Twilight Time” and twilight this past weekend when I was curious about the time of sunrise.  When I looked that up, I came across a reference to not one but three types of twilight.  Apparently there is a civil twilight, a nautical twilight and an astronomical twilight. Who knew?

Deepening shadows gather splendor
As day is done
Fingers of night will soon surrender
The setting sun
I count the moments darling
Till you’re here with me
Together at last at twilight time

According to Wikipedia (from which I have egregiously taken most of the material for this post), twilight is the time between dawn and sunrise or between sunset and dusk, during which sunlight scattering in the upper atmosphere illuminates the lower atmosphere, and the surface of the earth is neither completely lit nor completely dark. The sun itself is not directly visible because it is below the horizon.

Here in the after-glow of day
We keep our rendezvous beneath the blue
Here in the sweet and same old way
I fall in love again as I did then

Morning civil twilight begins when the geometric center of the sun is 6° below the horizon (civil dawn) and ends at sunrise. Evening civil twilight begins at sunset and ends when the geometric center of the sun reaches 6° below the horizon (civil dusk).

The brightest stars appear during the civil twilight, as well as planets, such as Venus, which is known as the “morning star” or “evening star.” During this period there is enough light from the sun that artificial sources of light may not be needed to carry on outdoor activities. This concept is sometimes enshrined in laws, for example, when drivers of automobiles must turn on their headlights; when pilots may exercise the rights to fly aircraft; or if the crime of burglary is to be treated as nighttime burglary, which carries stiffer penalties in some jurisdictions. A fixed period (most commonly 30 minutes after sunset or before sunrise) is typically used in such statutes, rather than how many degrees the sun is below the horizon. Civil twilight can also be described as the limit at which twilight illumination is sufficient, under clear weather conditions, for terrestrial objects to be clearly distinguished; at the beginning of morning civil twilight, or end of evening civil twilight, the horizon is clearly defined and the brightest stars are visible under clear atmospheric conditions.

Deep in the dark your kiss will thrill me
Like days of old
Lighting the spark of love that fills me
With dreams untold
Each day I pray for evening just
To be with you
Together at last at twilight time

Nautical twilight is the time when the center of the sun is between 6° and 12° below the horizon. In general, nautical twilight ends when navigation via the horizon at sea is no longer possible.

During nautical twilight, sailors can take reliable star sightings of well-known stars, using a visible horizon for reference. The end of this period in the evening, or its beginning in the morning, is also the time at which traces of illumination near the sunset or sunrise point of the horizon are very difficult, if not impossible, to discern (this often being referred to as “first light” before civil dawn and “nightfall” after civil dusk). At the beginning of nautical twilight in the morning (nautical dawn), or at the end of nautical twilight in the evening (nautical dusk)—under good atmospheric conditions and in the absence of other illumination—general outlines of ground objects may be distinguishable, but detailed outdoor operations are not possible, and the horizon is indistinct.
 
Astronomical twilight is the time when the center of the sun is between 12° and 18° below the horizon. From the end of astronomical twilight in the evening to the beginning of astronomical twilight in the morning, the sky (away from urban light pollution) is dark enough for all astronomical observations.

For anyone who lives on Mars, twilight is longer than on Earth, lasting for up to two hours before sunrise or after sunset. Dust high in the atmosphere scatters light to the night side of the planet. Similar twilights are seen on Earth following major volcanic eruptions.

Dusk, dawn, twilight, whatever, I hope you enjoy at least one of these marvels of nature today!

Here’s a link to the Platters’ version of “Twilight Time”:  http://www.youtube.com/watch?v=mZpwRCw_wJI&feature=related

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