Geoscience Reference
In-Depth Information
Celestial Dome
To enhance your understanding of Sun angle and seasonality, go
to the Geo Media Library and select
Celestial Dome
. This ani-
mation provides an opportunity to interact with an animated ce-
lestial dome. Change the latitude from several options to observe
seasonal change in the arc of the Sun, and its height above the
horizon at equinox and solstice. Be sure to notice how the Sun
arc and angle vary between low- and high-latitude locations, as
well as between the hemispheres. Be sure to answer the ques-
tions at the end of the exercise to ensure you understand this
concept.
Sun Angle and Length of Day
Let's now take a comprehensive look at Earth-Sun geomet-
ric relationships and how they influence the length of day. Go
once again to the Geo Media Library and select
Sun Angle
and Length of Day
. As you watch this animation, notice how
and why day length at three different latitudes varies over the
course of the year. Relate your observations with the
Celestial
Dome
animation and Table 3.1. After you complete the anima-
tion, be sure to answer the questions at the end of the exercise
to test your understanding of this concept.
Earth-Sun Geometry and Ancient Humans
Earth-Sun geometric relationships have been important to
people for a long time. Although ancient humans did not know
that Earth revolves around the Sun, they nevertheless under-
stood that Sun angle and day length changed over the course
of the year and were somehow associated with the seasons. In
many prehistoric human cultures, these changes had important
spiritual significance because they were related to agricultural
cycles. To learn more about how ancient humans celebrated the
Sun, go to the Geo Media Library
and select
Earth-Sun Geom-
etry and Ancient Humans
. After you watch the video, be sure
to answer the questions at the end of the exercise to test your
understanding of this concept.
VISUAL CONCEPT CHECK
3.2
This cross section of the Eastern Time Zone in the United States ranges from Boston, Massachusetts,
on the east to Holland, Michigan, on the west. Although both cities occur at the same line of latitude
(42° N), the timing of sunrise and sunset varies between the two locations. The Sun rises about an
hour earlier in Boston than it does in Holland. Conversely, the Sun sets about an hour later in Holland
than it does in Boston. Considering the rotation of Earth and basic Earth-Sun geometry, why does this
variation occur?
Sun's rays
Boston, MA
Lake
Michigan
Holland, MI
Atlantic Ocean
