The dramatic changes in the understanding and perception of our cosmic environment, initially triggered by the Cretaceous-Tertiary (K/T) boundary controversy during the early 1980s, appear to have gradually shifted from the geological to the historical time-frame.
During the last decade, most scientists have accepted the idea of global catastrophes caused by the impact of extraterrestrial bodies. Until fairly recently, their acceptance depended on the assumption that cosmic disasters were restricted to primordial times, millions of years before the origin of homo sapiens. This picture has changed significantly over the last couple of years. One of the most noticeable changes to the 1980s, which focused primarily on the demise of the dinosaurs and other mass extinctions, is the growing concern and risk assessment of the celestial threat to civilisation.
Scholars have now started to investigate the implications of catastrophic events on societal evolution, cultural anthropology, human social behaviour and the development of religion. Some of Britain's leading astronomers argue that both the emergence and the collapse of civilisations might be associated with episodes of increased meteoric activity, multiple impacts and related climate change. Such episodes punctuating the evolution of human cultures are now looked upon as a primary agency determining the rise and fall of ancient civilisations.
The emerging paradigm of historical catastrophism also stems from the awareness that the celestial hazard is not limited to the odd giant asteroid which hits the Earth every 100,000 or 1,000,000 years. In contrast to the traditional risk assessment - based on a statistical analysis of the number of known impact craters on the Moon and Earth in addition to the currently known asteroidal flux - it has become evident that super-Tunguskas (i.e. multimegaton atmospheric or oceanic impacts) are also capable of triggering ecological and climatical downturns which, if severe enough, may result in civilisation collapse.
In spite of mankind's rude awakening, there is no need for desperation or apocalyptic fatalism. Terrestrial life has now, for the first time ever, developed the intelligence and technology to discern the mortal dangers from space. It has also evolved to such a level that effective strategies of planetary defense can be devised and implemented. By turning away Near Earth Objects (NEOs) and the threat they pose to civilisation, man has acquired the capability of changing the course of nature and halting the vicious cycle of cosmic cataclysms. Scientists have the responsibility to meet this challenge head-on and to ensure that mankind takes its fate into its own hands. This would certainly mark the start of a new turning point in the development of cosmic consciousness and auto-evolution.
Benny J. Peiser (Liverpool John Moores University) Invited Talk at the National Science Foundation, Washington DC 20 November 1997