AS Science In Society 1.10
Teacher Notes
Introduction
The activity looks at key evidence from observation of the phases of
Venus, with a final part that has a similar structure to that of ‘So, you think
the Earth is round’ and likewise deals with the nature of theory, providing
a revisit to those sophisticated ideas.
Resources
Student worksheets
Textbook page 162
The activity
Students compare geocentric and heliocentric theories, the
predictions the theories make, and whether they are falsified
or supported by their predictions. In the first part they
complete a template comparing actual observations with
expectations based on the two theories. In the second part,
another template, similar to that used in Lesson 1 (relating to
round Earth and flat Earth theories) is completed.
The following websites provides an excellent ‘animation’ of the
phases of Venus:
http://apod.gsfc.nasa.gov/apod/ap060110.html
An important point is that the observed complete cycle of the
phases of Venus changes from full disc (with the planet
appearing smaller) through to vanishing crescent (with the
planet appearing larger). Geocentric theory predicts complete
cycles that do not follow this pattern.
How Science Works
Comments on the application of HSW
ideas in this activity.
Cd, Cg, Ch
Students experience the idea that scientific
conclusions can be supported but not
proved absolutely, but can be falsified by
evidence. A useful illustration to share with
students is that of the black swan. An
observer might establish what seems to be
a ‘law’ always obeyed – a law that states
that all swans are white, by arguing:
All the swans I have ever seen have been
white Therefore the next swan I see will be
white
The observer’s prediction may well turn
out to be correct, but it is not a matter of
absolute truth. A single sighting of a black
swan is enough to falsify or qualify the
observer’s generalised ideas. All scientific
conclusions, like the law of the whiteness
of swans, is provisional, and always
exposed to the threat of falsification by
observation. An established scientific
theory is still, however, the best available
match of ideas with observations made so
far.
July 2008
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Copies may be made for UK in schools and colleges
AS Science In Society 1.10
Student sheets
Introduction
Heliocentric and geocentric theories once competed for acceptance. Heliocentric theory is now
established scientific theory, and all observations since it was first developed in its modern form about
400 years ago have supported this theory. No observation has ever falsified it, and so it is the best
theory we have.
As Venus moves in the sky, we sometimes seem a smaller complete round sunlit disc. At other times we
see just a sunlit crescent, because the dark side of the planet is, mostly, facing us. These changes are
called the phases of Venus.
Activity
Part 1 – drawing the phases of Venus
The first part of the diagram (i) represents an observed cycle of the phases of Venus.
The second part (ii) shows a heliocentric representation of the relative positions of Earth, Sun and
Venus. On this it is possible to work out which parts of the sunny side of Venus we can see at different
times. Some of the circles that represent Venus have been shaded darkly, to show the sides of Venus
that face away from the Sun. Shade the other representations, or not, as appropriate, to show the dark
and sunlit sides.
Copy the shadings in to a linear sequence, to create a ‘heliocentric prediction’.
Now do the same for the third part (iii). Again, some of the representations of Venus, at different times in
its cycle of phases, have been shaded for you. Shade the rest as appropriate, and copy the sequence
onto the ‘geocentric prediction’ below.
(i)
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AS Science In Society 1.10
Student sheets
(ii)
(iii)
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AS Science In Society 1.10
Student sheets
Part 2 – falsification or support?
Fill in the gaps in the following table.
Theory
Geocentric theory
Heliocentric theory
Initial
observation that
suggests the
truth of theory
Every day, the Sun rises from one
direction and sets in the opposite
direction.
The time for the Sun to appear to
move through the zodiac is the same
as the time for one cycle of the
Earth’s seasons.
Prediction that
can be used to
falsify or support
the theory
How the
observation was
made of the
phases of Venus
The predicted pattern of the phases
of Venus
The predicted pattern of the phases
of Venus
Whether the
observation
falsifies,
supports or
proves the theory
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©The Nuffield Foundation, 2008
Copies may be made for UK in schools and colleges