lecture2 - Lecture2 EarthCentredUniverse

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    Lecture 2 Earth-Centred Universe What can we learn without modern instruments? What can we learn without modern instruments? The celestial sphere Constellations Celestial Coordinates The Sun’s Motion Across the Sky  The Ecliptic The Sun and Seasons  The Calendar.      
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    The Celestial Sphere   1.  Celestial sphere  is the imaginary sphere of  heavenly objects that seems to center on the  observer. 2.  Celestial pole  is the point on the celestial sphere  directly above a pole of the Earth. 
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    Because of  their daily  motion,  objects in the  sky appear to  be on a sphere  surrounding  the Earth.
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    Constellations 1. A  constellation  (from the Latin, meaning “stars  together”) is an area of the sky containing a  pattern of stars named for a particular object,  animal or person. 2. The earliest constellations were defined by the  Sumerians as early as 2000 B.C. 3. The 88 constellations used today were  established by international agreement. They  cover the entire celestial sphere and have  specific boundaries.
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    Orion
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    Agreed boundaries between constellations.
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    Constellations (cont.)  4. Constellations are simply accidental patterns of  stars. The stars in a constellation are at different  distances from us and move relative to each  other in different directions and with different  speeds.  5. Astronomers use constellations as a convenient  way to identify parts of the sky.
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    Measuring the Positions
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lecture2 - Lecture2 EarthCentredUniverse

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