1. The Day of the Sun's Return, The Winter Solstice
Montgomery College Planetarium
at Takoma Park/Silver Spring
By Dr. Harold Williams
December 21, 2016 version

2. One People … One Sky …Two Seasons

5. 1980 Winter Solstice at Stonehenge

6. Lawrence Hall of Science, CA Sunstone, resent

7. Amaterasu appearing from the cave on the Winter Solstice

8. Citron hot water of the Winter Solstice Yuzuyu, Katori City Japan

9. Locri Pinax Persephone Opens Likon Mystikon.

10. Frederic Leighton-The Return of Persephone (1891)
FredericLeighton-TheReturnofPerspephone(1891)

18. Length of Seasons Summer 93 days 15 hours 29 minutes
Autumn 89 days 20 hours
Winter 88 days 23 hours 54 minutes
Spring 92 days 18 hours 26 minutes
Sun and Earth closest, perihelion
Around January 3 or 4
Sun and Earth furtherest, aphelion
Around July 4

19. Obliquity of the ecliptic
23 ½ degrees, approximately, between day axis of rotation and year axis of revolutionary orbit about the sun
Causes the seasons
Seasons are not caused by the fact that the Earth’s orbit is not a perfect circle, but its orbit is slightly elliptical.
This ellipticity of the Earth orbit does cause the seasons which are caused by the tilt, obliquity of the ecliptic, to be slightly unequal in length.

20. Seasonal Years Mean tropical year is 365.242 189 670 SI days
vernal equinox: ×a days
northern solstice: ×a days
autumn equinox: − ×a days
southern solstice: − ×a days
Average tropical year is currently.
as in Julian years from 2000
(a in Julian years from 2000)

21. Winter Solstice Links

22. How to tell time
Using the sun and moving to uniform watch time!
Until 1833, the equation of time was tabulated in the sense 'mean minus apparent solar time' in the British Nautical Almanac and Astronomical Ephemeris published for the years 1767 onwards. Before the issue for 1834, all times in the almanac were in apparent solar time, because time aboard ship was most often determined by observing the Sun.

23. Equation of Time
Graph showing the equation of time (red solid line) along with its two main components plotted separately, the part due to the obliquity of the ecliptic (mauve broken line) and the part due to the Sun's varying apparent speed along the ecliptic due to the eccentricity & ellipticity of the Earth's orbit (dark dash-dotted line) used in