Volcanoes

Then astronomer Kevin Pang of the California Institute of Technology (Caltech) noted that 1628 B.C. and 1159 B.C. roughly mark the beginning and end of the Shang Dynasty of Bronze Age China. Both ends of the dynasty featured, according to ancient Chinese texts, environmental disasters - dimming of the sun and summer frosts that caused crop failures and famine. Pang notes also the Chinese concept of "mandate of heaven," wherein a dynasty reigned only as long as it protected the well-being of its people. This notion might have originated in the coincidence of dynastic change and climatic disaster. The Caltech team also noted similar descriptions from A.D. 536-545 that describe climatic disruptions that led to catastrophic famines and great loss of life. Much was going on in the world around these three dates. The four centuries of the Greek Dark Ages, which began after the Mycenaean era of mainland Greece collapsed amid great social upheaval, are thought to have begun in the twelfth century B.C. This period also saw the end of the once-mighty Hittite civilization of Anatolia in the Near East and of Bronze Age Israel.

The situation in Egypt is more ambiguous. Egypt's prosperous New Kingdom grew out of a century or so of warfare and upheaval known as the Second Intermediate Period, which itself followed the end of the Middle Kingdom. The New Kingdom has been dated from 1550 B.C. to 1070 B.C. While that is 70 years later than our two dates (1628 B.C. and 1159 B.C.), the time span is almost exactly the same. Some scholars have questioned traditional Egyptian dating, and it seems possible the timing of the New Kingdom, some 3,500 years ago, might be a little off. Then the volcano hypothesis began to dim. Volcanologists noted that volcanoes normally would not be powerful enough to collapse dynasties - the dust and acid, even if sufficient to dim sunlight, washes out of the atmosphere within a few years. And a review of the ice-core evidence from Greenland failed completely to confirm an exceptional volcanic eruption at A.D. 540.

It appears now that something far more damaging than volcanoes may have been at work here, especially after seeing unassailable proof that comets can hit planets: the extraordinary spectacle of comet Shoemaker-Levy 9 crashing into Jupiter in 1994. Comets appear in Chinese records of events at the beginning and end of the Shang dynasty. Were the catastrophic environmental downturns at 1628 B.C., 1159 B.C., and A.D. 540 caused by encounters with comets? Archaeologists and astrophysicists do not necessarily read each other's work, and it mostly escaped notice that three British cometary astrophysicists - Mark Bailey, Victor Clube, and Bill Napier - had published a highly relevant paper in 1990. They wrote that Earth had been at increased risk of bombardment by cometary debris in the period A.D. 400-600. They based their conclusion on the increased number of great meteor showers during that period.