The Bridge V Learning Edition 1 ; our solar system | Page 36

Develop a feeling of the vast distances in the Solar System, relative to the planet sizes: the Solar
System consists mostly of empty space. Learn to calculate these distances with scales.
Background Science
The planets’ distances to the Sun and to each other are huge compared to their sizes. Thus, one
cannot sensibly depict all planets together. Consequently, composite photographs are used in
many textbooks. This may create the false impression that the distances between all planets are
the same!
To fix this, you can construct a model of the Solar System yourself!
If you want to construct a model of our planetary system, you have to get a sense of the sizes of
the celestial bodies and their distances from the Sun. Then you will realise that you have to use a
different scale for the planet sizes than for their mutual distances. Otherwise, either the planets’
paths will be several kilometres long or the planets become so small that they can’t be seen.
The following table reproduces the distances and sizes of the planets (sources for columns 1 and
2: dtv-Atlas Astronomie, 2005).
If you prefer to build a small planetary system, you can also interpret the distance from the Sun
column as specifications in cm: the only important aspect is the ratios between these numbers.
Neptune would then be 2.25 m from the Sun.
Celestial body Diameter in
reality [km] Diameter scale
1:1.39 billion
[cm] Distance from
Sun in reality
[million km] Distance from
Sun scale 1:20
billion [m]
Sun
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune 1,392,000
4,878
12,104
12,756
6,794
142,984
120,536
51,118
49,528 100.0
0.35
0.87
0.92
0.49
10.27
8.66
3.67
3.56 -
57.9
108.2
149.6
227.9
778.3
1427.0
2869.6
4496.6 -
2.9
5.4
7.5
11.4
38.9
71.4
143.5
224.8
Full description
•
Take the children outside, preferably to an open space (e.g., a lawn in a park).
•
Divide the children into ten groups and assign one ball to each group.
•
Starting from the edge of the park, ask the children to move away from you according to
the distances in the right column of the table. Now they have made a (somewhat) realistic model
of the Solar System.
•
Notice the large distances: the Solar System mainly consists of vast emptiness! In reality,
the distances should even be 20 times larger! Because the balls would then get too small, doing
so would not be practical. Using a scale of 1:1.39 billion, all planets have acceptable sizes, but
Neptune would be 3.2 km from the Sun. On the other hand, with the use of a scale of 1:20 billion,
Neptune would be only 225.4 m away from the Sun, but some planet diameters would be less
than 1 mm. Therefore, using two different scales is indeed practical, while still giving the children
a good sense of the vast distances in our Solar System.