Figure 1 Drawing chalk outlines round
shadows can be a starting point
NIGHT AND
DAY
it’s obvious
how it works,
isn’t it?
Bob Kibble provides an insight into this
seemingly simple idea and explores why we
should teach children something which will
shortly have to be ‘unlearned’
C
an you always believe
your eyes? An obvious
daily occurrence is the
‘movement’ – of course it is an
apparent ‘movement’ – of the Sun
across the sky. Children might
draw chalk outlines around
their shadows in the playground
and see that, as the day passes,
the shape and direction of the
shadow changes (Figure 1).
Shadows of course pose their
own cognitive challenges. Does
a shadow really exist; is it real?
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Can you capture a piece of it?
Where does it go to on a cloudy
day? Linking shadows to light
sources and objects is likely to
be part of this early shadows
learning journey. The Sun and
the shadows it casts also provide
an excellent opportunity to do
some science learning outside
the classroom. Teachers will help
children to see that activities
such as drawing in chalk around
shadows lead to the creation of
primitive sundials, ‘sun-clocks’,
Jan/Feb 2011
which work on the changing
position of the Sun. Helping
children to notice that the Sun
moves across the sky is a target
for primary educators. Helping
them to appreciate that this is an
optical illusion is also a target.
However, also on the
learning agenda is the target
of understanding how night
and day actually happen. To
move towards a satisfactory
appreciation of the night and
day story, that is, that we are
night and day
living on a spinning Earth, is
not a trivial cognitive hurdle.
Not only has the idea of a huge
round object, the Earth, to be
appreciated, but also that we
live on it, that it is turning, that
we don’t fall off and that we
don’t notice this movement;
these represent a huge set of
challenges. This alone, would
be a tall order for any learner
in a primary classroom. But
if you have engaged in early
work on sunshine and shadows,
noting that the moving Sun
is responsible for changing
playground shadows leads to the
establishment of an alternative
day/night model: that of the Sun
orbiting the Earth once a day. In
teaching about the moving Sun
have we made the journey for
learners an uphill struggle?
It might be argued that
we should not entertain any
activities such as the ‘sun-clock’
in the playground, which might
support and give credence to
an erroneous model for night
and day. Why teach children
something that will shortly have
to be ‘unlearned’? I have some
empathy for this argument, but in
the end can’t support it. There are
so many staging posts along the
science journey that tell only part
of the story, be it a story about
the colours in rainbows, about
energy in food, about how bones
are connected or how the heart
works. These partial stories form
helpful staging posts along their
learning journeys. The sunshine
and playground shadow
exploration includes some very
good science: observation,
measurement and recording,
prediction and explanations. So
good was this science that for
thousands of years until the time
of Galileo, when the Copernican
revolution changed our way of
thinking, science and technology
used the orbiting Sun model to
build some of the great edifices
(pyramids, Stonehenge, the great
observatory in Jaipur) and lay
the foundations of modern space
science.
The moving Sun: an optical
illusion?
However, it is our duty as
teachers to offer the turning
Earth as an alternative model for
explaining night and day. One
might say that we should do more
than offer the alternative model
– we need to convince children
that the moving Sun is just an
optical illusion. We have the job of
being so convincing that children
will be persuaded to relinquish a
moving Sun in favour of a turning
Earth. In rising to this challenge,
at least we don’t have the might of
papal dogma to circumnavigate!
We only have the intuitive
and common-sense personal
conceptions of a class of young
thinkers, perhaps fuelled by earlier
work on playground shadows and
stories that use the language of
sunset and sunrise. So how should
we plan for this change?
One strategy would be to
acknowledge from an early
stage, that what we see is not the
Sun moving, but the ‘apparent’
movement of the Sun. The
Sun only appears to move. It
is an optical illusion. Such a
sophisticated
notion of ‘things
which appear to be so but aren’t’ is
a cognitive challenge for learners
age 7–9. How might such a story of
apparent deceit be supported? You
might make use of some simple
optical illusions, where drawings
appear to be misleading, which
could help children to appreciate
that you can’t always believe your
eyes. Does the classroom spin when
we turn around or does it just feel
like it? I dare say that many teachers
would want to generate such
thought challenges as part of their
night/day teaching strategy. I have
certainly done so.
Sundial and stories on a
globe
An approach that I have tried,
with some success, is to build
a story around the changing
direction of playground shadows.
I would start, as many teachers
do, with an illuminated globe to
show half in shadow and half in
‘daylight’. A strong table lamp
would provide a convenient
‘Sun’. Two plasticine figures
placed on opposite sides of the
globe form the players in the
emerging story. One character,
let’s call her Morag, lives in the
UK and decides to telephone her
new Facebook friend, Lucy. Lucy
lives in Hong Kong. How might
the conversation go (Figure 2)?
The modelling clay figures can
be replaced with a mini sundial,
made from thin card and using
a short length of matchstick as
a shadow stick. With the same
illumination as before, the
shadow stick will cast a shadow
and pupils can be invited to tell
you the time
as shown on the
sundial. Now let’s explore how
we can show the time changing
on our dial. There are two
alternatives. The first is to move
the table lamp/Sun from side
to side, while keeping the dial
illuminated. The shadow will
fall on different hours – the time
is changing just as it changed
on our playground ‘sun-clocks’.
Alternatively, we can hold the
lamp/Sun steady and turn the
globe slowly. Sure enough, the
sundial will show different
times – once again just as our
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Jan/Feb 2011
Figure 2 Morag
and Lucy in
conversation –
one at midday
and the other at
midnight
19
night and day
Figure 3 (right) A strong
lamp and globe can show
sundial times changing
when the lamp moves and
when the Earth spins
Figure 4 (below) Example of
a question sheet to assess
ideas held about movement
of shadows
Figure 5 (bottom) Example
of a question sheet to
assess ideas held about
night and day
correct answer. There really
isn’t one critical experiment or
demonstration that, in a primary
classroom, will prove to learners
that the Earth turns and the Sun
does not orbit the Earth. This
sundial demonstration is the best
shot I can offer. However, I do
believe that, if done well (which
means linking it to earlier work on
playground shadows and sundials,
and teasing out learner voices to
explain to you and to each other
just what is happening), such a
story provides a valuable stepping
stone for learners in their journey
from moving Sun to turning Earth.
playground clock did.
These two demonstrations are
easy to do with a small group of
about ten learners in a darkened
corner, perhaps while others
are occupied on ongoing group
tasks. Of course, here you are
offering two models to explain
the changing direction of sundial
shadows. Both have exactly the
same effect on the dial. If you lived
next to this dial you would have no
way of knowing which of the two
explanations was correct. Perhaps
it was the Sun that was moving;
perhaps it was the Earth that was
turning.
I am afraid that I can’t offer
you the million-dollar solution
that would seal the deal on the
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night and day
Diagnostic questions
How many children entering
your classroom already have
a day/night explanation that
employs a turning Earth? The
answer to this question will
reveal how great the challenge
is ahead of you. This question
ought to be of interest to most
teachers, along with questions
such as ‘What are children thinking
after my teaching of this topic?’
It is rare to find yourself with
the opportunity to engage in
formative assessment, other than
in real time during your teaching
– perhaps via a concept cartoon
(Naylor and Keogh, 2000) or a
mind-map, or through listening
to learners sharing ideas with
a third party such as a puppet.
I have used a simple diagram
and tick-box response sheet
to help me assess the range of
thinking about night and day
prior to teaching middle-agerange primary classes. A similar
question offered at the end of the
teaching can tell you something
about conceptual changes,
particularly if you allow a few
weeks to pass before offering the
‘after’ question. Figures 4 and 5
illustrate two possible question
sheets that might help you to
assess learning before and after
teaching.
Conclusion
So where has this left us? There
is no doubt that learners are
motivated by space and all ideas
associated with it. There is also
no shortage of schools where this
interest is captured by making
scale models of the solar system
or doing ‘research’ on facts
about the planets. There may be
some value in the former but I
can’t find much in the latter. In
reaching out into the conceptual
arena as described here, I am
offering teachers a route towards
enriching learning by engaging
with one of the great ideas in
science. The night and day
story has a place in the history
of ideas, in the challenges to
human perception, in challenging
‘common sense’ and the thorny
area of belief and dogma. It is far
more significant for learners than
remembering a mnemonic for
naming the planets!
Reference
Naylor, S. and Keogh, B. (2000)
Concept cartoons in science
education. Sandbach: Millgate
House.
Find out more
You can read more about
these strategies, together with
further ideas about teaching
using shadows and sundials, in
Sunshine, shadows and stone
circles written by the author
and available from Millgate
House Publications,
www.millgatehouse.co.uk
Bob Kibble is senior lecturer
in science education at the
University of Edinburgh and a
past Chair of the Association
for Science Education.
Email: [email protected]
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