From ce599e4f9f94b4eb00c1b5edb85bce5431ab3df2 Mon Sep 17 00:00:00 2001 From: toma Date: Wed, 25 Nov 2009 17:56:58 +0000 Subject: 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 --- doc/kstars/retrograde.docbook | 44 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 doc/kstars/retrograde.docbook (limited to 'doc/kstars/retrograde.docbook') diff --git a/doc/kstars/retrograde.docbook b/doc/kstars/retrograde.docbook new file mode 100644 index 00000000..00f200ab --- /dev/null +++ b/doc/kstars/retrograde.docbook @@ -0,0 +1,44 @@ + + + +John +Cirillo + + +Retrograde Motion +Retrograde Motion + + + +Retrograde Motion is the orbital motion of a body in a +direction opposite that which is normal to spatial bodies within a given system. + +When we observe the sky, we expect most objects to appear to move in a +particular direction with the passing of time. The apparent motion of +most bodies in the sky is from east to west. However it is possible to +observe a body moving west to east, such as an artificial satellite or +space shuttle that is orbiting eastward. This orbit is +considered Retrograde Motion. + +Retrograde Motion is most often used in reference to the +motion of the outer planets (Mars, Jupiter, Saturn, and so forth). +Though these planets appear to move from east to west on a nightly +basis in response to the spin of the Earth, they are actually drifting +slowly eastward with respect to the stationary stars, which can be +observed by noting the position of these planets for several nights in a +row. This motion is normal for these planets, however, and not +considered Retrograde Motion. However, since the Earth completes its +orbit in a shorter period of time than these outer planets, we +occasionally overtake an outer planet, like a faster car on a +multiple-lane highway. When this occurs, the planet we are passing will +first appear to stop its eastward drift, and it will then +appear to drift back toward the west. This is Retrograde Motion, since +it is in a direction opposite that which is typical for planets. Finally, +as the Earth swings past the the planet in its orbit, they appear to +resume their normal west-to-east drift on successive nights. + +This Retrograde Motion of the planets puzzled ancient Greek +astronomers, and was one reason why they named these bodies planets +which in Greek means wanderers. + + -- cgit v1.2.1