Copy the KDE 3.5 branch to branches/trinity for new KDE 3.5 features.

BUG:215923


git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/kdeedu@1054174 283d02a7-25f6-0310-bc7c-ecb5cbfe19da

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+<sect1 id="ai-flux">
+
+<sect1info>
+
+<author>
+<firstname>Jasem</firstname>
+<surname>Mutlaq</surname>
+<affiliation><address>
+</address></affiliation>
+</author>
+</sect1info>
+
+<title>Flux</title>
+<indexterm><primary>Flux</primary>
+<seealso>Luminosity</seealso>
+</indexterm>
+
+<para>
+The <firstterm>flux</firstterm> is the amount of energy that passes through a unit area each second.
+</para>
+
+<para>
+Astronomers use flux to denote the apparent brightness of a celestial body. The apparent brightness is defined as the the amount of light received from a star
+above the earth atmosphere passing through a unit area each second. Therefore, the apparent brightness is simply the flux we receive from a star.
+</para>
+
+<para>
+The flux measures the <emphasis>rate of flow</emphasis> of energy that passes through each cm^2 (or any unit area) of an object's surface each second.
+The detected flux depends on the distance from the source that radiates the energy. This is because the energy has to spread over a volume of space before it reaches us.
+Let us assume that we have an imaginary balloon that encloses a star. Each dot on the balloon represents a unit of energy emitted from the star. Initially, the dots in an area
+of one cm^2 are in close proximity to each other and the flux (energy emitted per square centimeter per second) is high. After a distance d, the volume and surface area of the
+balloon increased causing the dots to <emphasis>spread away</emphasis> from each. Consequently, the number of dots (or energy) enclosed in one cm^2 has decreased as illustrated in Figure 1.
+</para>
+
+<para>
+<mediaobject>
+<imageobject>
+<imagedata fileref="flux.png" format="PNG"/>
+</imageobject>
+<caption><para><phrase>Figure 1</phrase></para></caption>
+</mediaobject>
+</para>
+
+<para>
+The flux is inversely proportional to distance by a simple r^2 relation. Therefore, if the distance is doubled, we receive 1/2^2 or 1/4th of the original flux.
+From a fundamental standpoint, the flux is the <link linkend="ai-luminosity">luminosity</link> per unit area:
+
+<mediaobject>
+<imageobject>
+<imagedata fileref="flux1.png" format="PNG"/>
+</imageobject>
+</mediaobject>
+</para>
+
+<para>
+where (4 * PI * R^2) is the surface area of a sphere (or a balloon!) with a radius R.
+Flux is measured in Watts/m^2/s or as commonly used by astronomers: Ergs/cm^2/s.
+For example, the luminosity of the sun is L = 3.90 * 10^26 W. That is, in one second the sun radiates 3.90 * 10^26 joules of energy into space. Thus, the flux we receive
+passing through one square centimeter from the sun at a distance of one AU (1.496 * 10^13 cm) is:
+</para>
+
+<para>
+<mediaobject>
+<imageobject>
+<imagedata fileref="flux2.png" format="PNG"/>
+</imageobject>
+</mediaobject>
+</para>
+</sect1>