麻豆传媒

WHEN 麻豆传媒鈥檚 readers and reporters recorded their
impressions of this year鈥檚 eclipse*, they were following a tradition dating back
to 899 BC. So say Chinese astronomers who believe they have pushed back the date
of the earliest documented solar eclipse by nearly 200 years.

Their claim centres on the Bamboo Chronicle, a text transcribed in
the 3rd century AD from inscriptions carved into bamboo unearthed from the tomb
of King Wei Xiang, who ruled around 500 BC. 鈥淒uring the first year of King Yi,鈥�
the chronicle notes, 鈥渢he day dawned twice at Zheng.鈥� This king is thought to
have reigned somewhere between 1100 and 840 BC, and the town then known as Zheng
lay near the city of Xi鈥檃n.

Now a team comprising Ciyuan Liu of the National Astronomical Observatories
in Lintong, Jianke Li, currently at the Australian National University in
Canberra, and Xiaolu Zhou of Northwest University in Xi鈥檃n has calculated that
such an event could only have occurred on 21 April 899 BC. 鈥淭here is only one,鈥�
says Li.

The Chinese eclipse of 899 BC was 鈥渁nnular鈥�, which means the rim of the Sun
remained visible. But the researchers say there would have been a noticeable
darkening in the sky. If the eclipse was near dawn, people would have seen the
sky mysteriously brighten, darken, then brighten again鈥攁 second dawn.

Their claim is controversial, however. 鈥淚n the whole of Chinese history there
is no other mention of a double dawn,鈥� says Richard Stephenson of the University
of Durham, who has studied the history of Chinese astronomy. He argues that
eclipses were well understood by the ancient Chinese. The earliest record of a
solar eclipse claimed before now, dating from 708 BC, is also from
China鈥攁nd its chroniclers clearly knew they were watching the Moon passing
over the face of the Sun. Li, however, maintains that astronomers were still
ignorant of solar eclipses in the Xi鈥檃n region in 899 BC.

Stephenson also questions the Bamboo Chronicle鈥檚 authenticity, as it
was copied from inscriptions lost many centuries ago. But if Li鈥檚 claim can be
proved, it will allow astronomers to calculate the rate at which the Earth鈥檚
spin is slowing by comparing the location of the ancient eclipse with the
predictions of modern theory (麻豆传媒, 30 January, p 30). 鈥淭he
further back we can go the more accurate our estimates,鈥� says Li.