UNESCO resource kit - science and technology educa...

UNESCO Module 25: Understanding eclipses of the Sun r -----------------
More eclipse ideas
This picture was drawn in the sixteenth century. It
shows how an eclipse.of the Sun happens when the
Moon blocks off the Sun's light.
People understood eclipses over 2000 years ago,
and they were able to predict when an eclipse
would happen. But later; in the Middle Ages, this
knowledge was forgotten. When an eclipse
happened, people were taken by surprise. They
thought that the gods were displeased, and that
some dreadful fate was about to befall them.
In the sixteenth and seventeenth centuries, European scientists worked out the
details of the planets' orbits round the Sun. They saw the planets as bodies
m.oving with the precision of clockwork. Eclipses could be predicted to the
minute and were anticipated with great excitement by astronomers and the
educated people of the towns. Here is what someone wrote about the total solar
eclipse of 8 April 1652:
"The country people tilling loosed theirploughs. The birds dropped to theground. //
And here is what Francis Baily, an English astronomer, wrote in his account of
the total eclipse of 1842:
/7was astounded by a tremendous burstofapplause from the street below: and atthesamemomentwaselectrified atthe
sightofoneofthemostbrilliantand splendid phenomena thatcan be imagined, for that instant the dark body of the Moon
was suddenly surrounded with a corona/akind of bright glOly fa saintly halo/ aspainted by medieval artists} ....But the
mostremarkablecircumstanceattendingthe phenomenonwastheappearanceofthreeIargeprotuberancesapparently
emanating from the circumference of the Moon but evidently forming aportion of the corona.//
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Baily had read many eyewitness accounts of eclipses, but this was the first one
he had seen for himself. He had not anticipated anything so magnificent. At the
same time, he declared that there was /I something in its singular and wonderful
appearance that was appalling."
Another astronomer, Francois Arago, observed the same eclipse in the south of
France. A murmur of excitement built up as totality approached, to be replaced
by a profound calm. As the Sun returned it was greeted with /I transports of joy
and frantic applause." Eclipses had become a spectacle of great public interest,
and they still are today ..
1 Look at the picture at the top of the page. Identify the Sun, the Moon and
the Earth. Find the Sun's rays and the shadow of the Moon. Did the artist
understand why eclipses happen?
2 Find out about the Sun's corona. Today, we call the 'protuberances' which
Francis Baily saw 'prominences'. What are they? Do they come from the
Moon or the Sun?
.3 How have people's reactions to eclipses changed in the last 2000 years?