Day
A day is any of several different units of time. The word refers either to the period of light when the Sun is above the local horizon or to the full day covering a dark and a light period. Different definitions of the day are based on the apparent motion of the Sun across the sky (solar day). The reason for this apparent motion is the rotation of the Earth around its axis, as well as the revolution of the Earth in an orbit around the Sun.Ancient custom has a new day start at either the rise or set of the Sun on the local horizon. The exact moment, and the interval beween two sunrises or two sunsets, depends on the geographical position (longitude as well as latitude), and the time of year.
A more constant day can be defined by the Sun passing through the local meridian, which happens at local noon (upper culmination[?]) or midnight (lower culmination[?]). The exact moment is dependent on the geographical longitude, and to a lesser extent on the time of the year. The length of a such a day is nearly constant. This is the time as indicated by sundials.
A further improvement defines a fictituous mean Sun that moves with constant speed over the equator; the speed is the same as the average speed of the real Sun, but this removes the variation over a year as the Earth runs its orbit around the Sun.
For civil purposes, since the middle of the 19th century when railroads with regular schedules came into use, a common clock time has been defined for an entire region based on the mean local solar time at some central meridian. For the whole world, about 30 such time zones are defined. The main one is "world time" or UTC (Coordinated Universal Time).
The present common convention has the civil day start at midnight, which is near the time of the lower culmination[?] of the mean Sun on the central meridian of the time zone. A day is commonly divided into 24 hours of 60 minutes of 60 seconds each.
When taking leap seconds into account, a civil clock day is 86400 or 86401 SI seconds long (or theoretically 86399 s on occasion, which never happened).
In astronomy also the sidereal day is used; it is ca. 3 minutes 56 seconds shorter than the solar day, and close to the actual rotation period of the Earth.
in a frenzy of laughter. She expected that this, or something else,
But that her desire to go should contain a vague joy, that she should
neat apartment, Madame Marmet had lived since the death of her husband.html">husband.
Countess Martin found her in her modest drawing-room, opposite
remained ever faithful to her. He it was who, the day after M. Marmet's
delivered by Schmoll. She had fainted in his arms. Madame Marmet
dined together often with rich friends.
Madame Martin, slender and erect in her zibeline corsage opening on a
good.html">good man, who was susceptible to the graces of women. He had told her
she had not been frightened at night by pictures of the earth.html">earth devoured by
gallantry, she looked at the mahogany bookcase. There were not many
amazed one to see in this good lady's house.html">house that Etruscan warrior wearing
vases of gilded porcelain, and carved images of the Virgin, picked up at
books which her husband had left. Of all the ancient objects collected
persons had tried to sell it for her. Paul Vence had obtained from the
would not part with it. It seemed to her that if she lost that warrior
worthily, and would cease to be the widow of Louis Marmet of the Academie
a phenomenon is very improbable."
Madame Martin replied that she knew no serious reason why the earth and
cataclysm would come as late as possible.
She looked at him. His bald head could boast only a few hairs dyed
hung in loose folds, and one divined that his body was equally withered.
pretty little house, the windows of which overlook the Botanical Gardens?
.
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