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Astronomy for Dummies III: Observational astronomy and clock systemBY: informationishere | Category: Education | Post Date: 2008-08-19
Observational astronomy has developed through ages and civilizations. Ancient Greece, Egypt, India, China etc. have done significant work of tabulating and managing data about stars and constellations, planets and their motion in the sky, the sun, moon and a lot of other things related to astronomy. Almost every ancient civilization has linked the stars to the supernatural and that is where the zodiac astrology comes into picture. In this article, we will talk about both aspects in brief. In principle, the zodiacs are constellations through which the Sun appears to pass in its yearly journey across the Earth sky. The yearly journey of Sun corresponds to the relative motion of Sun due to the revolution of Earth around the Sun. These constellations were demarcated long ago by the Greeks as well as the Egyptians and many other civilizations. However the currently accepted zodiacs in order are: 1 Aries 2 Taurus 3 Gemini 4 Cancer 5 Leo 6 Virgo 7 Libra 8 Scorpio 9 Sagittarius 10 Capricorns 11 Aquarius 12 Pisces These in astrology cover approximately 30 degrees each of the Sun's path and are fixed in the sky. They are related to the birth, life and the death of a person depending on the position of the Sun in these zodiacs at a particular time. However, in astronomy, the actual region covered by these constellations is highly variable. In fact, the is another constellation named Ophiuchus which also lies in the Sun's path. This constellation is popularly known in astronomy as the thirteenth zodiac. Due to a certain phenomena known as precession, the zodiacs have been shifting and that has led to the Sun cutting across Ophiuchus in its path. The planets also almost always lie in the zodiacal belt since most of the planets have their orbit with a very small tilt to the Earth's orbit. Zodiacal light etc. are some features that occur due to the interplanetary dust. Now, let us jump to the conventions. One major convention used is the clock system. If I have a star in the sky and I need to point to another star relative to it, I can either simply point to that second star or I can give directions. The problem with direct pointing comes when you are pointing to someone slightly far from you. There is a problem of parallax and can lead to ambiguities in what you are pointing at. So, we need to give directions. What is generally done on a local scale is to use a clock system. We assume that there is a clock located at the first star with 12 o clock pointing at zenith. Now, the directions can be given by the position of the hour hand e.g. 4 o clock , 8 o clock etc. This works well for stars which are reasonably close to each other. Other directional terms used are the cardinal directions like North, South-East etc. Another important thing is measuring approximate angles using your hands. This should be read up online as it would require pictorial explanation. Article Source: http://www.saching.com About Author / Additional Info: Part 1: http://www.saching.com/Article/Astronomy-For-Dummies---Astronomy-For-Beginners/260 Part 2: http://www.saching.com/Article/Astronomy-for-dummies---II/303 Mehul Jain IIT Bombay AstroNUT Additional Articles: * What is Angina? Heart Problems, Angina Symptoms and Natural Remedies * Advantages and disadvantages of a small car * The negative effect of rock music on youth * The role of Human Resource Professionals in a company * Alcoholism: How to know that you are drinking too much alcohol? Does this article violate or infringe on your copyright ? It is a violation of our terms for authors to submit content which they did not write and claim it as their own. If this article infringes on your copyrights, then use our Contact us form with the detailed proof of infringement along with the offending article's title, URL and writer name. If you do not hear back from us then contact us again in another 10 days. Thank you. Comments on this article: (0 comments so far) * Additional comments are now closed for this article *
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