- published: 05 Feb 2009
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Solar time is a reckoning of the passage of time based on the Sun's position in the sky. The fundamental unit of solar time is the day. Two types of solar time are apparent solar time (sundial time) and mean solar time (clock time).
Fix a tall pole vertically in the ground; at some instant during any sunny day the shadow points exactly north or south (or disappears, if the sun is directly overhead). That instant is local apparent noon-- 1200 local apparent time. About 24 hours later the shadow will again point north/south, the sun seeming to have covered a 360-degree arc around the earth's axis. When the sun has covered exactly 15 of that 360 degrees (both angles being measured in a plane perpendicular to the earth's axis), local apparent time is 1300 exactly; after 15 more degrees it will be 1400 exactly.
The problem is that in September the sun takes less time (as measured by an accurate clock) to make an apparent revolution than it does in December; nowadays 24 "hours" of solar time can be 21 seconds less or 29 seconds more than 24 hours of clock time. As explained in the Equation of Time article, this annoyance is due to the ellipticity of the Earth's orbit and the fact that the Earth's axis is not perpendicular to the plane of its orbit.
Solar may refer to:
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun, also known as daytime. The period of time measured from local noon to the following local noon is called a solar day.
Several definitions of this universal human concept are used according to context, need and convenience. In 1967, the second was redefined in terms of the wavelength of light, and it became the SI base unit of time. The unit of measurement for time called "day", redefined in 1967 as 86,400 SI seconds and symbolized d, is not an SI unit, but it is accepted for use with SI. A civil day is usually also 86,400 seconds, plus or minus a possible leap second in Coordinated Universal Time UTC, and, in some locations, occasionally plus or minus an hour when changing from or to daylight saving time. The word day may also refer to a day of the week or to a calendar date, as in answer to the question "On which day?" Day also refers to the part of the day that is not night — also known as 'daytime'. The life patterns of humans and many other species are related to Earth's solar day and the cycle of day and night (see circadian rhythms).
When the day warmth starts to fade away
When the stars are drawn sharply in the sky
When the breath of night wind touches your face
When the crimson moon rises high
Sleeping nature, calm my boiling soul
Open up your gates, let me walk inside
Am I deaf or still I'll hear your call
Can I see the night's endless light
Still we stand in silence all as one
Those who've found the way through the darkness' tide
Those who've come to night realm and are gone