Download The Seasons Interactive - Home

Seasons Interactive-1 of 7
The Seasons Interactive
Brief Summary
This exhibit, a portable free standing table, allows a facilitator to illustrate why we have four
seasons. A six-inch moveable Earth globe is mounted so that half the Earth is always half
illuminated by a flashlight as the Earth moves around the sun. Also, Earth always retains its
23.5 degree tilt. In addition THE SEASONS TABLE can be used to expand the conversation with
visitors into other related areas such as eclipses, important geographic lines on the globe
such as the Arctic Circle and the Tropic of Cancer, and precession of the equinoxes and the
North Star.
It is worth noting that this cart was originally conceived and prototyped by the Monday
Morning and Wednesday Afternoon Galaxy Guide teams.
Equipment Required
THE SEASONS TABLE,
an
exhibit similar to the
PHASES
OF
THE
MOON
TABLE,
but smaller, can
be set up and used by
one person.
Props:
 Graph paper
 Moon on a stick
 Toy top.
Facilitating with THE SEASONS TABLE
Setting up THE SEASONS TABLE.
Set-Up Procedure







Roll the cart to a place near light but not flooded with light. You want the globe’s sunny
side to be distinctly different from the shaded side.
Remove the four legs from their holders, place them into their sockets and tighten the
knobs. (Note: the knobs have to be tightened up snuggly so that the legs will not fall
out when the table is tipped.)
Twist the propeller-like stays that hold the table on the cart, and gently tip it onto the
floor.
Note that the table is stored so that the month of May is at the top with the globe held
by a bungee cord.
Remove the bungee that holds the globe in place.
Once the table is upright, rotate it so that December is on the north side towards the
Mars diorama. This way, the axis of the Earth points at approximately true north.
Keep the props handy.
Seasons Interactive-2 of 7
Main Teaching Points
Story #1: Interpreting the physical facts of the model. (A prerequisite to all the stories.)
1. A day equals one complete rotation of the Earth on its axis.
2. A year is represented by the Earth circling the table once.
3. The table surface represents the plane of the earth’s orbit around the sun.
4. The opposite season to fall is spring. The opposite of winter is summer. (Many school
age children do not know this.)
5. The tilt of the Earth globe in its holder represents the earth’s axis leaning over. The tilt
of the axis is 23½ degrees (as compared to standing straight up.) This degree of tilt
never changes.
6. The two equinoxes occur on or about March 21 and September 21. The summer
solstice (also called mid-summer’s day) occurs on or about June 21. The winter
solstice (aka mid-winters day) occurs on or about Dec 21. These four dates change
because we insert a leap year day every fourth year.
Story #2 The causes of the seasons
1. The Earth goes around the sun so that two things always remain constant: The tilt of
the axis at 23.5 degrees, and the fact that half the Earth is always in light and half in
the dark.
2. The seasons are caused by the shifting of the amount of light that is received by each
hemisphere of the Earth as it orbits the sun.
3. The tilt of the axis contributes to the seasons in two ways:
a. Longer summer days allow for the collection of more energy from the sun.
b. The light hitting the surface in summer is concentrated onto a smaller area of
the surface than the same amount of energy in the winter, when that fixed
amount of energy is distributed over a greater area.
4. The daily high temperatures around the spring equinox day, March 21 are lower than
those around September 21 (the fall equinox date) because of thermal inertia, the
tendency of the Earth to retain its temperature. The hottest week of the year in
Colorado is in July, four weeks after midsummer’s day.
Story #3 Eclipses
1. The small moon prop that resembles a lollipop is nearly true to scale of size of the
earth, but not to the distance scale. It should be out at 30 Earth diameters away.
This is a surprisingly large distance of six paces.
2. Half of the moon is always illuminated, even if we don’t see that half.
3. Eclipses of the moon happen when the moon passes into the Earth’s shadow. The
process takes about three hours to complete. Total lunar eclipses occur about
every year and a half, though partial lunar eclipses are three times as common.
4. A solar eclipse happens when the shadow of the moon falls on the earth. (The
scale on our model here is not realistic because in reality the moon should be
placed over six paces away from earth.) The moon’s shadow in our model covers
half a continent, whereas in reality it is only about 1200 miles across, or as big as
the letter O in North America on the globe.
Another effect that is hard to show is that the moon’s orbit tilted at five degrees
compared to the plane of the earth’s orbit around the sun. This tilt of five degrees
Seasons Interactive-3 of 7
explains why eclipses of the sun and moon do not happen every month. With this
tilt of the moon’s orbit, five out of six times (on average) the moon’s shadow passes
above or below the plane of the earth’s orbit. Likewise, the moon, on the anti-solar
end of its orbit, passes below the earth’s shadow so no lunar eclipse occurs. The
tilt reduces the necessary alignments for eclipses to happen.
Story #4 The various lines on the globe.
1. At the North Pole, if the Earth had a perfectly smooth horizon the sun would set on
the evening of the fall equinox and not rise again till the morning of the spring
equinox. Except for a few weeks of twilight before sunrise and after sunset, the
North Pole experiences total darkness for half the year.
2. At every point on the Arctic Circle, the sun stays above the horizon for at least one
full 24-hour day. At a point a mile south of the Arctic Circle, the sun sets for at least
a minute or so, even on the summer solstice.
3. On the tropic of Cancer, a stick stuck straight into the ground (perpendicular to the
surface) will cast no shadow on one day of the year, the summer solstice. South of
the Tropic, the sun will pass over head two days a year. At the equator, the sun
passes overhead at noon on the equinox days.
4. The same physical events occur in the southern hemisphere with the Antarctic
Circle and the Tropic of Capricorn, but in the opposite seasons from the northern
hemisphere.
Story #5 Precession
1. The Earth spins like a toy top, or a coin that has been set on its edge and spun.
This turning motion, called precession, happens at a slower rate than the primary
spinning motion.
2. The Earth precesses in one giant circle every 26,000 years which equals about 1
degree every 70 years.
3. The three effects of precession are 1) to change what season that we see the
constellations in 2) to change the time of year that the Earth is closest to the sun
(perihelion point) or farthest from the sun (aphelion point) and 3) to change which
star the earth’s axis points to. The tilt of the earth’s axis does not change, but only
the star that lies above the Earth north pole.
Today the star Polaris lies above the
earth’s North Pole. In 3000 BC and
again in 23,000 AD the star above
the earth’s axis will be Thuban. The
Egyptians aligned some of their
buildings with Thuban. By about
15,000 AD, Vega will be a North Star,
but not as good a North Star as
Polaris, because it lies farther from
the path of the North Celestial Pole
than Polaris. In 21,000 AD, Deneb
will be another not-so-good North
Star. Finally, 26,000 years from
today, Polaris will again be the North
Star.
Seasons Interactive-4 of 7
Educational Strategy
The concepts involved in understanding the two main causes of the seasons look deceptively
simple. In fact, the explanation of the seasons probably confuses more adults and children
than any other space concept. This exhibit allows the facilitator to tell five “stories,” (that is,
five presentations and facilitation of related facts, observations and activities).
These stories range in difficulty from
#1. Interpreting the physical facts of the model.
#2. The causes of the seasons
#3. The causes of lunar and solar eclipses
#4. The physical significance of the lines on the globe, e.g., the Arctic Circle and the
Tropic of Cancer.
#5. Precession. This wobble affects three things. (See above Story #5 for details.)
Suggested ways of presenting demo
Try this:
If a visitor is at an early stage of learning about the seasons, (a child or naïve adult) use
only Stories #1 & #2.
 Illustrate what a year is, then what a day is and then a day and year combined.
 Illustrate the concept of opposite seasons and the equinoxes and solstices on the
calendar.
 Establish what tilt of the earth’s axis means, and illustrate by moving the globe around
the circle that it does not change.
 Move the globe to the spring equinox. Have visitors observe that the Earth is always
half in the light and half in the dark, and that only on the equinoxes days do both the
north and south poles get light at the same time. Otherwise, either the North Pole or
the South Pole get sunlight, but not both.
 If the axis of tilt and the illumination of the Earth don’t change, what does? Answer: In
summer, the light is not distributed evenly. One hemisphere gets more light than the
other and this makes it warmer there.
 Use the graph paper to show that when the rays of the flashlight hit the paper
perpendicularly, the light spot is smallest and the energy is most concentrated. As you
tilt the graph paper, the light falls on more and more squares. This means that the
energy on any square is now less concentrated per square foot than the light of
summer which is more concentrated. (be sure to define “concentrated” in kid-friendly
tenr, e.g. butter on toast.) Secondary factors aside, the more concentrated the light,
the higher the temperature.
If a visitor is at an intermediate stage of learning about the seasons: Review Stories #1 & #2
in brief, then draw out of the visitor the physical meaning of eclipses (Story #3) and/or the
lines on the globe (Story #4)
For the advanced visitor, draw out the facts of precession mentioned in Story #5.
Seasons Interactive-5 of 7
Operating Tips

Here’s a great question to facilitate a discussion: Where would you have to go on Earth to
get the maximum number of hours of sunshine in a year. (ANS: Everywhere on Earth is
identical in hours of sunlight per year, barring clouds and horizon obstacles such as
mountain ranges.)

It is important to keep from mixing stories together. Do all of one story along with its
enabling concepts, before moving onto another story.

Don’t try to tell all the stories to one set of visitors.
Questions and Answers
Is the model to scale? How far is the Moon from Earth?
The Moon is 240,000 miles from Earth, or about 30 Earth diameters. Demo: Show how far
away the Moon would be, and describe where the Sun would be. (Sun is 93 million miles
away, about 12,000 Earth diameters! Before you do the demo, measure out the distance of
30 globes so that you know where in Space Odyssey the Moon would be. During the demo,
ask a visitor to walk to where he or she thinks the moon would be. They will be surprised
when they find out the actual distance.) Explain that at this scale, the Sun would be at the
City Park Lake house ( ¾ of a mile away) about three stories in diameters..
What about eclipses?
A LUNAR ECLIPSE happens when the Earth comes between the Moon and the Sun. Demo:
Move Moon through orbit until it is on opposite side of Earth from Sun. Ask what phase Moon
must be in for lunar eclipse to happen (full moon). A SOLAR ECLIPSE happens when the
Moon passes between the Earth and the Sun. On Earth, a solar eclipse can be seen only
along a narrow path thousands of miles long on Earth. Demo: Move Moon through orbit until
it is on the same side of Earth as Sun. Moving Moon slowly, show area on Earth that would
experience solar eclipse. Ask visitors what phase Moon must be in when solar eclipse
happens (ANS: New moon).
Why don't eclipses occur every time there is a new Moon?
The plane of the Moon's orbit is tilted at five degrees from the plane of the Earth's orbit
around the Sun. This disturbs the critical alignments that make eclipses happen, reducing
them to only at most a few a year rather than every month.
Potential Problems

One of the difficulties of the concepts of seasons it that people (and kids in particular)
don’t know the supporting and enabling concepts involved. For example, the opposite
season of SPRING is FALL. Even some sixth graders don’t answer this immediately. THE
SEASONS TABLE is a way to teach verbal concepts, such as opposite seasons, day and year
using a visual representations. These enabling concepts must be acquired before any
understanding of the causes of season really sinks in..
Seasons Interactive-6 of 7
Background materials
collections links)
(websites,
videos,
articles,
digital
#1: Interpreting the physical facts of the model.
http://www.synapses.co.uk/astro/earthmot.html
#2. The causes of the seasons.
http://www.astronomy.org/programs/seasons/
#3: The causes of lunar and solar eclipses.
http://www.astro.umd.edu/resources/introastro/eclipses.html
#4. The physical significance of the lines on the globe, e.g., the Arctic Circle and the Tropic of
Cancer.
http://en.wikipedia.org/wiki/Circle_of_latitude
#5. Precession.
http://www.crystalinks.com/precession.html
Self assessment suggestions
After facilitating the SEASONS TABLE several times, complete the checklist and rubric below by
highlighting the box that best describes your performance. Have your team leader observe
your demo then complete an identical rubric. Discuss your presentation technique with your
team leader along the lines of the rubric.
A. Checklist of pre-requisite skills for facilitating SEASONS TABLE.
1. Knows how to store the table in the main storeroom.
2. Understands and can explain clearly the enabling teaching points of how the
sun appears to move: daily motion, and seasonal motion. Story #1.
3. Understands and can explain clearly the main teaching points of each of five
stories:
#2: Causes of the seasons
#3. Eclipses
#4 Lines on the Globe
#5 Precession
Seasons Interactive-7 of 7
B. Rubric for Galaxy Guides— SEASONS TABLE
PRESENTER_________
QUALITY
OK
LEVELS 
TRAITS
Individualizin Can run the activity
g
visitor by giving clear step
experience
by step instructions
to visitors of all ages
Attitude
durability
DATE________
COOL
WAY COOL
Can respond to visitors
on different levels: For
children concentrating on
the "arts & crafts" angle,
and for interested adults,
the apparent motions of
the sun
Remains pleasant and
patient throughout shift,
enjoys helping visitors,
does not get (visibly or
noticeably) tired during
shift
Asks
stimulating
questions to engage the
visitor at heightened level
When responding to a curious
and advanced visitor, can use
correctly and explain clearly the
terms, "sidereal," "mean solar
time" and place the sundial in a
historic context
Remains
pleasant
Finds ways to self-renew,
and
patient
continues to enjoy responding
throughout
shift,
to visitors with enthusiasm
even when repeating
while
recognizing
the
the same statements
uniqueness of each new visitor
over and over
Sparks
Directs
visitor
to
Understands
content
and
visitors’
digital collection or to
explains on appropriate level.
curiosity
other staff with more
Opens new subjects for inquiry
knowledge
Drive behind Asks
leading Draws visitor into asking Facilitates an open inquiry; lets
conversation questions
questions
visitor take lead in asking
questions
Clean up
Cleans
up
all Cleans up all materials Cleans up all materials used
materials used and used and stows them and stows them properly
stows them properly
properly
Improves
Discusses demo with Works with peers on Develops written goals and
demo
over peers
and evaluation,
implements strives to meet these goals, eg,
time
implements
new new techniques
“Raise Knowledge of exhibit
techniques
from OK to COOL by Sept.” or
“Raise all OK’s to COOL by
August”