Changes

When speaking of things having to do with the moon, the adjective ''lunar'' is used. The Greek-derived prefixed root ''selen-'' followed by the morpheme ''-o-'' is used as well; for example, the [[science]] of mapping the moon is called ''[[selenography]]'' (morphemes: ''selen-o-graph-y'').

When speaking of things having to do with the moon, the adjective ''lunar'' is used. The Greek-derived prefixed root ''selen-'' followed by the morpheme ''-o-'' is used as well; for example, the [[science]] of mapping the moon is called ''[[selenography]]'' (morphemes: ''selen-o-graph-y'').

==Tides==

==Tides==

The gravitational force of the Moon causes the ocean [[tides]]; these tidal forces have other effects as well. These tidal forces have the effect of creating resistance which slows down the rotation of both objects. In the case of the Earth, the result is that the Earth's rotation slows on the order of one millisecond per century. The Moon's rotation is locked in to its period of revolution, and the same side of the Moon always faces the Earth.

The gravitational force of the Moon causes the ocean [[tides]]; these tidal forces have other effects as well. These tidal forces have the effect of creating resistance which slows down the rotation of both objects. In the case of the Earth, the result is that the Earth's rotation slows on the order of one millisecond per century. The Moon's rotation is locked in to its period of revolution, and the same side of the Moon always faces the Earth.

==Libration defined==

==The "dark" or far side==

 

Due to a slight "wobble" in the lunar motion called ''libration,'' we actually see a little bit more than half of the Moon's surface; sometimes it is turned a bit one way and sometimes the other. However, nobody had any idea of what the far side of the Moon looked like until 1959, when a Soviet satellite photographed it and relayed pictures back.  

Due to a slight "wobble" in the lunar motion called ''libration,'' we actually see a little bit more than half of the Moon's surface; sometimes it is turned a bit one way and sometimes the other. However, nobody had any idea of what the far side of the Moon looked like until 1959, when a Soviet satellite photographed it and relayed pictures back.  

In the old Scottish ballad ''Sir Patrick Spens''<ref>Child, Francis James (1860), ''The English and Scottish Popular Ballads,'' [http://www.sacred-texts.com/neu/eng/child/ch058.htm No. 58]; the ballad is thought to refer to an actual event of the year A.D. 1290.</ref>, a sailor cautions:

In the old Scottish ballad ''Sir Patrick Spens''<ref>Child, Francis James (1860), ''The English and Scottish Popular Ballads,'' [http://www.sacred-texts.com/neu/eng/child/ch058.htm No. 58]; the ballad is thought to refer to an actual event of the year A.D. 1290.</ref>, a sailor cautions:

&nbsp;&nbsp;"I saw the new moon late yestreen<br>

:"I saw the new moon late yestreen

&nbsp;&nbsp;&nbsp;&nbsp;With the old moon in her arm;<br>

::With the old moon in her arm;

&nbsp;&nbsp;And if we go to sea, master,<br>

:And if we go to sea, master,

&nbsp;&nbsp;&nbsp;&nbsp;I fear we'll come to harm."<br>

::I fear we'll come to harm."

==Earthshine==

==Earthshine==

The effect known as "the old Moon in the new Moon's arms" can often be seen when the Moon is a narrow [[crescent]]. Within the intensely bright crescent, a dim and mysterious view of the entire circular moon is seen. The effect is also known as ''earthshine'' because it is light from the Sun reflected off the Earth to the Moon and back that lights up the darker portion of the Moon. The bright crescent is lit by the Sun and is in full daylight. The rest of the Moon is not lit by the Sun; but an [[astronaut]] standing in this area would see a "full Earth" dominating the nighttime sky, lighting it up by its earthshine. The brightness of Earthshine, and hence the visibility of the old Moon in the new Moon's arms, varies. When the Earth is covered with clouds, or when there is a lot of snow-pack on the side of the Earth facing the Moon, the Earth is a white and bright and the Earthshine is intense. When the Earth looks like a "big, blue marble," it is less intense.  

The effect known as "the old Moon in the new Moon's arms" can often be seen when the Moon is a narrow [[crescent]]. Within the intensely bright crescent, a dim and mysterious view of the entire circular moon is seen. The effect is also known as ''earthshine'' because it is light from the Sun reflected off the Earth to the Moon and back that lights up the darker portion of the Moon. The bright crescent is lit by the Sun and is in full daylight. The rest of the Moon is not lit by the Sun; but an [[astronaut]] standing in this area would see a "full Earth" dominating the nighttime sky, lighting it up by its earthshine. The brightness of Earthshine, and hence the visibility of the old Moon in the new Moon's arms, varies. When the Earth is covered with clouds, or when there is a lot of snow-pack on the side of the Earth facing the Moon, the Earth is a white and bright and the Earthshine is intense. When the Earth looks like a "big, blue marble," it is less intense.  

===A cute poem==

==Lunar calendars==

"The Old Moon in the New Moon's Arms" is the title of a poem by [[Ella Wheeler Wilcox]], in which she interprets the effect as the New Moon wishing that her lost love, the Old Moon, be in her arms one last time; Venus grants the wish, and:

Throughout history, many calendar systems have been based on the phases of the moon.

 

The months of the [[Islam|Muslim]] [[calendar]] are determined by observations of the [[hilal]], the moment at which the thin crescent moon first becomes visible. This marks the start of a month. Traditionally, and today in [[Pakistan]] and [[Jordan]], hilal is determined by actual observation and can be affected by weather and other factors. When following the traditional method, it is not actually possible to be certain precisely when future months will begin. In most Muslim countries, actual observation has been replaced by [[astronomy|astronomical]] rules.

==The moon in culture==

&nbsp;&nbsp;&nbsp;&nbsp;The Full Moon's shadowy shape shone on the night,<br>

&nbsp;&nbsp;&nbsp;&nbsp;Her phantom lover in the whole world's sight.<br>

The months of the [[Islam|Muslim]] [[calendar]] are determined by observations of the [[hilal]], the moment at which the thin crescent moon first becomes visible. This marks the start of a month. Traditionally, and today in [[Pakistan]] and [[Jordan]], hilal is determined by actual observation and can be affected by weather and other factors. When following the traditional method, it is not actually possible to be certain precisely when future months will begin. In most Muslim countries, actual observation has been replaced by [[astronomy|astronomical]] rules.

:Swift thro' the vapors and the golden mist&mdash;<br>

::The Full Moon's shadowy shape shone on the night,<br>

:The New Moon reached out clasping arms and kissed<br>

::Her phantom lover in the whole world's sight.<br>

== See also ==

== See also ==