One day in the year 2136 B.C., a hungry dragon tried to eat the sun. The Emperor of China and his people were terrified. At first, a tiny bite was taken out of one side of the orb. Then a quarter, a half and finally the whole sun was gone, and there was nothing but a circle of white light around the black space where the sun had been.
The frightened, but resourceful, Chinese knew what to do. They ran around in the strange twilight, shouting and screaming defiance at the dragon, beating drums, banging gongs, and whacking heavy wooden ducks until the startled dragon moved away. The sun was saved, but the Emperor, now more angry than scared, ordered that the Imperial Astronomers, Hsi and Ho, should be beheaded for failing to warn him in time of the dragon’s approach.
A total eclipse of the sun was seen at that time in China, but Hsi and Ho, as experienced astronomers should have predicted it, since eclipses occur periodically. What happens is that as the moon moves around the Earth and the Earth around the Sun, there are times when the three are lined up in such a way that the moon blocks out the Sun’s light for a period of up to 7 1/2 minutes.
Astronomers have long enjoyed the anonymous rhyme that has become their epitaph:Here lies the bodies of Hsi and Ho,
Whose fate, though sad, was visible:
Being killed because they did not spy
Th’ eclipse which was invisible