Seasons and the Elliptical Orbit
q Seasons
      Solstices: mark the longest and
shortest days of the years (June
21 and December 21 in the
northern hemisphere, the reverse
in the southern)
      Equinoxes: the length of night
and day become equal in each
hemisphere.
q At the present-day orbit, the
winter and summer solstices
differ from the aphelion and
perihelion by about 13 days.