Knowledge of the' Stars 161 



July in winter. Like the day, the year has its own 

 length. What determines the length of a day and of a 

 year? 



Fitting the calendar to the year. In the early history 

 of the world much confusion arose because of the lack 

 of a calendar, but before the beginning of the Christian 

 era, Julius Caesar, by the advice of the astronomer 

 Sosigenes, decreed that the calendar year should be 

 365^ days, every fourth year containing 366 days and 

 the others 365 days. The actual length of a year is al- 

 most 365 J days, but in 16 centuries the difference be- 

 tween the true length and 365^ days caused the seasons 

 to shift in reference to the calendar 10 days. To 

 remedy this, Pope Gregory in 1582 decreed that the 

 day following October 4 should that year be called 

 October 15, thus making up the 10 days. He further 

 decreed that the last year of each century should not 

 be a leap year unless divisible by 400. Thus 1700, 1800, 

 and 1900 were not leap years, although they are divisi- 

 ble by 4, but the year 2000 will be a leap year. This 

 arrangement so nearly approximates the length of the 

 real year that in 4000 years the seasons will shift not 

 more than i day. 



Astronomy the oldest of the sciences. When the 

 ancient Assyrians and Egyptians went on a journey, 

 they often traveled at night, for the day was hot. They 

 did not ride on a railroad train or along a highway with 

 a fence on either side, but guided their courses by the 

 stars. They had no electric or gas lights or such lamps as 

 ours, and so the light of the moon was more important to 

 them than it is to us. Whether on a journey or at home, 



