Rotation axis of the Earth is tilted 231/2 ° away from perpendicular to plane of ecliptic (fig. 1-22, 1-21, 1-20)
This means that one pole is facing toward the sun while the other pole is tilted away from the sun
As the Earth revolves around the sun, the N pole faces the sun when the sun is between the Earth and the North Star, but faces away from the sun when the Earth is between the sun and the North Star.
perihelion and aphelion (fig. 1-19)
C. Temperature variations
sun angle - angle of incidence
amount of heating and concentration of rays (fig. 1-23, 1-24)
atmospheric filtering
length of day - (Table 1-6)
tilt of rotation axis and circle of illumination (fig. 1-25)