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Solstices and Equinoxes
TEK 8.7A – the student knows the effects resulting from cyclical movements of the Sun, Earth, and Moon. The student is
expected to model and illustrate how the tilted Earth rotates on its axis, causing day and night, and revolves around the sun
causing changes in seasons.
The Earth in Space
How the Earth moves:
 Rotates on an axis
 Revolves around a star
We have named several phenomenon
beyond seasons. However, these also occur
in predictable cycles.
What is a Solstice?
At two points throughout the year, the tilt
of the Earth’s axis reaches its maximum
angle compared to the Sun, and then
begins to move back the other direction.
 This usually happens around June 21st
and December 21st.
 These days are known as solstices.

Solstice
These two times in the year, the summer
solstice and the winter solstice,
The sun reaches its highest (summer) or
lowest point (winter) in the sky at noon,
marked by the longest and shortest days.
Make a quick T chart
in your notes
Winter Solstice
Summer Solstice
Winter Solstice
• The northern hemisphere is pointed furthest away from
the sun
• The sun is directly over the Tropic of Capricorn
• The shortest day of the year, and the longest night in
the northern hemisphere
December 21,
2016 was our
most recent
Winter Solstice
Winter
Solstice for
Northern
Hemisphere
Summer
Solstice for
Southern
Hemisphere
Summer Solstice
• The northern hemisphere is pointed furthest toward the
sun
• The sun is directly over the Tropic of Cancer
• The longest day of the year in the northern hemisphere
June 20,
2017 is our
next
Summer
Solstice
Summer
Solstice for
Northern
Hemisphere
Winter
Solstice for
Southern
Hemisphere
Solstices



On two days each year, the noon sun is overhead
at either 23.5° S or 23.5° N – solstices.
Winter Solstice
 23.5° S
 in the northern hemisphere
 December 21st
 shortest day of the year
Summer Solstice
 23.5° N
 in the northern hemisphere
 June 21st
 Longest day of the year
Equinox
 Equinox:
the date (twice each year) at
which the sun crosses the equator
 The equinoxes are half-way between
the solstices
 Therefore, they occur in the spring
and fall
Equinoxes
 The
word Equinox is derived from
latin - aequus (equal)
and nox (plural: noctis) (night).

During the Spring and Fall
equinox the length of day versus
night is equal.
Make a quick T chart
in your notes
Spring Equinox
Fall Equinox
Spring and Fall Equinox
• Vernal (spring) and autumnal (fall) equinox the sun is directly over the equator
• Days and nights are equal in length
Vernal (Spring) Equinox

Occurs on or
around March 21st

Marks the
beginning of spring
in the northern
hemisphere
Autumnal (Fall) Equinox

Occurs on or
around September
23rd

Marks the
beginning of fall in
the northern
hemisphere
Equinox Video

Click on picture
Activity