THE EARTH AS A PART OF THE SOLAR SYSTEM 521 



Moon's phases. Each month the moon goes through 

 certain changes or phases, first showing a small crescent, 

 then increasing in size till the full moon is reached, and then 

 decreasing. Only that half of the moon is lighted that is 

 turned toward the sun, and the phase of the moon depends 

 on the part of this lighted portion that we can see. When 

 the moon is between the sun and earth we see none of the 

 lighted portion and this is the new moon; then as the 

 moon revolves around the earth a larger portion shows, 

 the first quarter; and when the moon is on the opposite 

 side of the earth from the sun we see the entire lighted 

 surface, the full moon. Then as it revolves through the 

 other half of its orbit, the lighted portion gradually grows 

 less. 



During this period of revolution the moon rotates once on 

 its axis, so that it always keeps the same surface towards 

 us. No human being has ever seen the other side of the 

 moon. 



Rising and setting of the moon. If the rising of the moon 

 be watched for a few weeks, it will be seen that it rises on 

 an average of about fifty minutes later each day. Sometimes 

 this difference may be thirty minutes, and again it may be 

 an hour and a quarter. There is also a difference in the 

 exact place in the horizon where the moon rises and sets. 

 Just as the sun has a north and a south motion in its place of 

 rising and setting during the year, so the moon has a north 

 and south motion during the month. 



HOME PROJECT 29 



Purpose. To observe the moon's changes for a month 



Directions. Notice the changes that take place in the moon 



with reference to the three following points: I. shape; 2. time 



of rising or setting; 3. place of rising or setting. Keep at 



least two records a week of as many points as you can as 



