THE EARTH'S PLACE IN THE UNIVERSE 27 



the house. Again in September the sunrise is at the east 

 point, but each day afterward it is farther south of east, 

 until December 21, when it is 23 J south of east. South 

 windows then get sunshine very early in the forenoon 

 and long after midday. 



18. The Sun's Position at Noon. Next in importance 

 to the position of the North Star is the position of an imagi- 

 nary line called the celestial meridian. This is a circle pass- 

 ing through the north point on the horizon, the zenith, and 

 the south point, and then around the other side of the earth 

 to the north point. It divides the sky into an east and a 



North Star 



FIG. 6. THE CELESTIAL MERIDIAN 



1. What part of a circle does the line NZS form? 2. How many degrees 

 from N to Z? 3. If the observer (O) is in lat. 30,what is the position of the 

 North Star on the meridian? (Answer in degrees from the nearest letter.) 

 4. The equator of the sky is about 90 from the North Star; locate the place 

 where it crosses the meridian, in the same way that you answered 3. 5. At 

 what times in the year is the sun on the equator? 



west half; and since the circle always 'passes through the 

 zenith, there is a celestial meridian for every observer. 

 When the sun or the moon crosses the meridian, it has 

 made half its daily journey from rising to setting. The 

 abbreviations a. m. and p. m. refer to the time when the 

 sun crosses the meridian. The letters a. m. stand for the 

 Latin ante meridiem, before midday; p. m. for post meridiem, 

 after midday. 



At noon the sun is on the meridian over the south point 

 in the horizon. In northern latitudes it is higher above 

 the horizon at noon in June than at any other time in the 



