THE DIMENSIONS OF TRAVEL 



into strange places, the sun's function as a compass becomes ever more im- 

 portant. Kramer (1951, 1952) has shown how the sun functions as a com- 

 pass for birds on the home range. With the sun as their only clue to direction 

 in the experimental cages, Kramer's Starlings moved with a directional bias 

 that held constant regardless of time of day. Without the sun, however, 

 their movements were random, favoring no direction. 



The daily change in the sun's position relative to earth and local time, 

 the change by which the seasons ebb and flow, is too obvious and well 

 known to merit discussion here. Let us merely recall that on any given day 

 of the year, the position of the sun varies according to locality. A traveler 

 who in autumn has moved several hundred miles toward the equator, for 

 example, perceives that the sun rises at a steeper angle from the east, fol- 

 lows a higher arc across the sky, and drops more abruptly into the west. The 

 interval between sunrise and sunset increases slightly, and the points where 

 the sun strikes the horizon at sunrise and sunset approach more closely to 

 due east and due west. Because of the more abrupt ascent to sunrise and 

 the descent after sunset, the duration of twilight is shortened ( Figure 23 ) . 



When a traveler moves across degrees of longitude, he perceives no 

 change in the sun's arc and the length of day; but in eastward travel, sun- 



vSUN ftT LOCAL (PE-lTA) NOON t OCT. 15 - 



&'■ At Dclta 



S^Attlk tkave-l due. Cast of Dellta 



^3; .. .. .. WL>5T .. 



fi* " - " vSOUTH- " 



<S y ■ " £>OUTHE.ft5T * " 



Figure 23. Travelers perceive changes in the sun's arc and schedule in direct proportion 

 to the speed, distance, and direction of travel. A mid-October traveler going from Delta 

 southeast to Lake Christina in one day would find the sun's arc higher (X-Y:A-B) and 

 its position (S 5 ) 12 minutes past zenith at Delta noon. From the dotted line it will be 

 seen that the angle of descent becomes more abrupt as the traveler moves southward. 



