The following resources
are intended to help children further explore the cycle of day
and night on Earth and other planets! These activities and materials
will enhance the Native American tale of Ant
Dances for Light, as
told by Dovie
Share the Story
After the program, invite the children to retell
the Native American story and the science story. This will help
them to revisit the content as a flowing narrative, not unrelated
facts, and underscore that both stories are a way of understanding
our universe. Storytelling will challenge the children to make
connections from one piece to the next and help identify where
they do not have an understanding of the material.
Help the children begin the Native American story, “What
was the first thing that happened in the coyote story?” Prompt
the children through the discussion by asking, "What happened
next?" Help the children remember incidents that are left
out or are out of order. You may wish to keep a list of events
as the children build the story. Follow the Native American narrative
with a discussion of the science story in the same way.
You may wish to have the children reenact the
story as a play, taking turns as the narrator. They can create
songs or dance the stories. Alternatively, invite the children
to illustrate each stage of the story and to connect the events
in the Native American story to the events in the science story
where they can.
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The Sun is Always Shining Somewhere. Allan
Fowler, 1992, Children's Book Press, ISBN 0516449060. Written
for young children, ages 4–8, this book explores the Sun
as a star and why there is day and night.
Why do We have Day and Night. Anthony
Lewis, 1996, Heinemann Educational Books — Library
Division, ISBN 0600587797. A clear, well-illustrated discussion
of day and night cycles for young children ages 4–8. Moon
phases and seasons are also presented.
Day and Night (Let's Explore Series). Henry
Pluckrose, 2001, Gareth Stevens, ISBN 0836829581. The
reasons for day and night are presented in easy-to-read text
with large print and photographs for young children, ages 4–8.
Fundamental concepts of day and night and their effects on people.
What Makes Day and Night? Franklyn Branley,
1999, Bt Bound Publishers, ISBN 0808523775. Branley
presents an illustrated explanation of Earth's rotation in a
straightforward manner for children (ages 7–8). The
text includes an experiment to demonstrate the concept of day
Beyond the Blue Horizon: Myths and Legends of the
Sun, Moon, Stars and Planets. E. C.Krupp, 1992,
Oxford University Press, ASIN 0195078004. In this
book for adults, Krupp explores how sky lore is woven into civilizations
around the world from ancient to modern .
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Earth, Sun and Moon. (Earth Science-Astronomy
Series) Visual Learning Company, 2003, ISBN 1592340555.
The causes of daylight, seasons, and Moon phases are explored in this video
for older children (ages 11–14). A teacher's guide is available.
Native American Star Tales. Lynn Moroney, Astronomical
Society of the Pacific. Children
and adults will enjoy these audiocassettes of Native American
sky legends told by storyteller Lynn Moroney.
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Space Place of NASA's Jet Propulsion Laboratory provides for
children an overview of Earth's rotation and how the period is changing.
NASA Kids shares a brief explanation for children of the changing
length of days through an exploration of the seasons. Includes an
animation of the seasons and vocabulary explanations.
The Astronomical Applications Department of the United States
Naval Observatory presents a wealth of background information and
data concerning astronomical events, calendars, time, Sun and Moon
rise and set times, Moon phases, and more for the adult audience.
Earth Moon Viewer, developed by John Walker of Fourmilab, is
an interactive package that allows children and adults to view Earth
daylight/darkness from a variety of viewpoints. Visitors can manipulate
location and time of viewing. The basic map can be found at http://www.fourmilab.ch/cgi-bin/uncgi/Earth/action?opt=-p
The American Museum of Natural History presents background information,
activities, data, and resources for educators to facilitate investigations
of the extended length of days in Antarctica.
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Why does Earth have day and night?
Day and night cycles are caused by Earth's spin on its axis.
Earth turns or rotates one time every 24 hours. The part of
Earth that is facing the Sun experiences day, and the part facing
away from the Sun experiences night. As Earth spins counterclockwise
(viewed from above the North Pole) the region of daylight moves across
the globe from east to west.
Do other planets have day and night?
All the planets in the solar system spin on their axes (so does
the Sun!) and so they have day and night cycles. There are differences,
however, in the length of day and night. Some planets rotate faster
than Earth and some rotate slower. Mars has a day/night cycle similar
to Earth. Mars rotates on its axis once every 24.6 hours. Venus turns
once on its axis every 243 Earth days (which is a little longer than
it takes for Venus to go around the Sun!). The larger planets spin
much faster. Jupiter rotates once every 10 hours, Saturn spins once
every 11 hours, and Neptune completes a rotation in 16 hours. Pluto,
at the farthest reaches of the solar system, spins on its axis once
every 6.4 days.
Why does Earth's day length change during the year?
Every location on Earth experiences an average of
12 hours of light per day, but the actual number of hours
of daylight on any particular day of the year varies from place to
place. Locations around Earth's equator receive about 12 hours
of light each day. In contrast, the North Pole receives 24 hours
of daylight for a few months in the summer and total darkness for
months in the winter. These two annual times of light and dark are
separated by a long sunrise and a long sunset.
Earth rotates on its axis; this causes us to experience day and
night. But Earth's axis is tilted 23.5 degrees (the angle is measured
between Earth's equatorial plane and the plane in which it orbits
the Sun). As Earth revolves around the Sun, the axis points toward
the same location in space, almost directly toward Polaris, the
North Star. This means that during our movement around their Sun
each year, our polar regions spend long periods pointed toward the
Sun in the summer (for example, July in the Northern Hemisphere,
or December in the Southern Hemisphere) and long periods pointed
away from the Sun during the winter. At latitudes greater than 66.5
degrees (90 degrees minus 23.5, the tilt of the axis), the regions
above the Arctic and Antarctic circles on our globe, days of constant
darkness or light can occur.
Because of this tilt and our movement around the Sun, there is a
time when Earth's North Pole is tilting 23.5 degrees toward the Sun.
This is the Summer Solstice, the first day of the Northern Hemisphere
summer and the longest day of the year in the Northern Hemisphere.
On December 21 or 22, our North Pole is tilting 23.5 degrees
away from the Sun and the South Pole is tilted toward the Sun. This
is the Winter Solstice, the shortest day of the year in the Northern
Hemisphere. Twice each year, during the Equinoxes (“equal nights”),
Earth's axis is not pointed toward the Sun. The Spring Equinox in
March marks the beginning of the transition from 24 hours of darkness
to 24 hours of daylight at the North Pole. The Fall Equinox in September
marks the shift into 24 hours of darkness at the North Pole. During
the Equinoxes, every location on Earth (excluding the extreme
poles) experiences a 12-hour day time period.
Other planets also experience these changes in the length of day
and night because they, too, are tilted on their axes. Each planet's
axis is tilted at a different angle. Jupiter is tilted only 3 degrees,
so its change in the lengyh of day and night as it moves around
the Sun is less extreme than that of Earth. Neptune's axis is tilted
30 degrees; day and night changes would be more extreme on Neptune
than on Earth. Uranus presents an interesting case because its axial
tilt is even more extreme, 98 degrees! This means that the north
pole of Uranus is pointed at the Sun during the north polar summer;
the south pole is in total darkness. During the north pole winter,
some 42 Earth years later, the south polar axis points at the Sun
and the north polar region is in total darkness. During the spring
and fall, when its axis is perpendicular to the incoming rays of
the Sun, Uranus experiences a 17-hour day and night cycle as it spins
on its axis.
Good news for overachievers: Earth's days are getting longer!
Researchers examining ancient corals noted that annual growth patterns
suggested there were more days in a year in Fossil corals from the
Devonian Period (380 million years ago) recorded 400 daily cycles.
About 290 million years ago in the Pennsylvanian Period, there were
390 daily cycles each year. Assuming that Earth's revolution around
the Sun has not changed dramatically, this means that the number
of hours per day has been increasing and that Earth's rotation has
been slowing. Today, the length of a day is 24 hours. During the
Pennsylvanian Period a day was ~22.4 hours long. In the Devonian
Period, a day was ~21.8 hours long. Earth's rotation appears to be
slowing approximately 2 seconds every 100,000 years. Why are Earth
days getting longer? Some scientists suggest that tidal cycles create
a “drag” on
Earth, causing it to slow down.
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