THE SOUTHWORTH PLANETARIUM
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43.6667° N                   70.2667° W
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 2458837.16
2019-2020:  LXXV
             "In the depth of winter I finally learned that there was in me
an invincible summer."
                             -Albert Camus

THE DAILY ASTRONOMER
Thursday, December 19, 2019
Solstice Q and A

Astronomical autumn is drawing to a close.   In fact, tomorrow is the last
full day of autumn.  Winter will start the next day, albeit at a late hour.
   While winter's onset can engender dread in even the heartiest souls, it
is not without its beauty.  If you don't believe me, go out and observe a
fresh snowscape below a rising ember moon.     Today we welcome
astronomical winter's arrival with a brief Q and A: solstice questions
we've collected over the years.


*When will the winter solstice occur this year?*
Saturday, December 21st at 11:19 p.m.
At this precise moment, the North Pole will be aligned away from the Sun as
far as it can be.  Astronomical winter will officially begin.

*Why is the term "December solstice" preferable to "winter solstice?"*
Simply because it is more accurate.       The December solstice will mark
the beginning of the Northern Hemisphere's astronomical winter and the
Southern Hemisphere's astronomical summer.   The summer solstice is more
accurately known as the "June solstice."

*Is winter really our shortest season?*
Did you ever hear the old adage:   New England has only two seasons:
 winter and Independence Day.   Well, New Englanders can be forgiven for
not believing that winter is our shortest season, for it certainly seems
interminable, especially during the April blizzards that we all adore.
However, astronomically, winter is truly the shortest season.  It lasts
about 88 - 89 days, whereas summer is about 93 days in duration.

 Why?

Winter occurs when the northern hemisphere is directed away from the Sun.
Refer to the image below.

[image: cycle_seasons1.jpg]

The amount of time Earth requires to move from the winter (December)
solstice point to the spring (March) equinox is shorter than the time it
requires to move between any of the other seasonal points because in early
January Earth reaches perihelion, the closest point in its orbit around the
Sun.   A planet revolves more rapidly when it is closer to the Sun.
Around July 4th, Earth reaches aphelion, its greatest distance from the
Sun.    Therefore, Earth is moving faster in January and February than it
is traveling in July and August.    If Earth reached perihelion in July,
our summer would be the shortest season.

*Since you can balance an egg on its end on the equinox, I assume you can
lay an egg on its side on the solstice?*
Are you serious?
Actually, a person can balance an egg on its end on any date of the year,
provided they don't have any other commitments and are endowed with saintly
patience.  This popular misconception is based on the mistaken idea that
Earth is actually "upright" on the equinox.  It isn't.   Earth's tilt
remains the same throughout the year.

*Is the Sun directly overhead at the equator on the winter solstice?*
No.  The Sun passes directly overhead at the Tropic of Capricorn on the
winter solstice.   It passes directly overhead along the Tropic of Cancer
on the summer solstice.   The Sun passes directly overhead along the
equator on the spring and autumn equinox.

*What season is it on the Equator?*
The Equator is a line of no thickness. If you're standing on the Equator,
the part of you in the southern hemisphere will be in one season and the
part on the northern side will be in another season.

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