Static model of site; can be used with light source to simulate a mid-summer's morning.
What it shows:
1:50 scale model of the Stonehenge site with the positions of Sun
and Moon on important dates marked. It can be used with a light
show to reproduce Sunrise on Midsummer's morning, June 21.
How it works:
The Stonehenge site consists of the sarsen circle of 30 megaliths
capped with 30 lintels. Within this circle is a horseshoe pattern
of five trilithons. 80m north-east of the circle's center is the
Heel Stone; it is the alignment of this stone with the Sun that is
relevant on Mid-summer's morning. The 1:50 scale model (1m = 2cm)
is made of wood on a 90×90cm plywood base. The heel stone, 160cm
from the center of the circle, sits on a separate 120×120cm base
for ease of mobility. Figure 1 shows the layout of the
Stonehenge site (accurate ground plans in references 1, 2);
Figure 2 shows model measurements of the sarsen stones,
trilithons and Heel Stone.
figure 1. Sarsen circle and trilithon horseshoe
figure 1 Labels:
1. Midsummer sunrise
2. Winter moonrise low point
3. Midwinter Sunrise
4. Southern moonrise (minimum)
5. Southern moonrise (maximum)
6. Midwinter sunset
7. Northern moonset (minimum)
8. Northern moonset (maximum)
9. Midsummer sunset
10. Winter moonrise high point
figure 2. Model stone dimensions
A slide projector on a mobile tripod (see details in Setting it
up) can simulate the positions of the Sun at various times of
the year, and especially at the Summer solstice. On the morning of
June 21st, the Sun rises up behind the Heel Stone, casting a shadow
through the sarsen circle to the center of the trilithon horseshoe.
The projector bulb is fitted with a dimmer, so that the Sunrise
begins a dull deep red, getting brighter as is rises into the
morning sky.
Setting it up:
The slide projector is loaded with a masking slide with a half
inch circular hole and mounted on a heavy wheeled tripod with
elevating head. The bulb dimmer is a silicon controlled rectifier,
a commercially available household dimmer switch that plugs
straight into the projector. These are prone to blowing and should
be tested before each show. The Stonehenge model itself sits on a
cart, with the slide projector operating 2-3m distant. Owen
Gingerich, creator and Master of Ceremonies, accompanies the
midsummer event with Also Sprach Zarathustra by Richard
Strauss.
Comments:
The model represents the complete structure of Stonehenge III,
constructed around 2100 B.C. Further details of the site, including
the older Stonehenges, are available in the references. Due to
precession, the Sun now rises slightly to the left of the Heel
Stone, but due to its leaning, rises to pass over its tip. Wheeling
the tripod, adjusting projector height and controlling the dimmer
is a three handed operation; some practice is called for. Musical
accompaniment to the dramatic sunrise has traditionally been
Strauss' Also Sprach Zarathrustra, although Spinal Tap's
Stonehenge would be a fitting alternative.
References:
1. Hawkes, J., Sci. Am. June 1953, pp.25-31
2. Brecher, K., Feirtag, M., Astronomy of the Ancients (MIT
Press, 1979) pp.117-132
3. Daniel, G., Sci. Am. July 1980, pp.78-90
4. Heggie, D. C., Megalithic Science (Thames & Hudson,
1981) pp.195-206
5. Krupp, E. C., Echoes of Ancient Skies (Harper & Row,
1983) pp.214-223