Timescales relating to human development and the terrestrial environment

Phenomenon Timescale*
Giant comets injected into short-period orbits 100,000 yr
Orbital evolution of Chiron 100,000 yr
Significant evolution of zodiacal cloud 1,000 – 50,000 yr
Lifetime of giant comet 10,000 – 30,000 + yr
Interval since maximum extent of last ice age 18,000 yr
End of continental glaciation 10,000 yr
Lifetime of typical meteor stream 500-5,000 yr
Significant evolution of giant comet debris 1,000-5,000 yr
Significant evolution of Taurid meteor stream 1,000-5,000 yr
Lifetime of normal active comet 300-1,500 yr
Beginning of homo sapiens 40,000 yr
Beginning of food production and domestication 10,000 yr
First civilizations; irrigation; cuneiform texts 5,000 yr
Constellation building (main epoch) 5,000 yr
Oldest celestial myths 3,000-5,000 yr
Main epoch of megalith and ziggurat building 3,000-5,000 yr
Earliest calendars 3,000 yr
Well documented history less than 2,000 yr

*Very approximate. The slowness of human development during the ice age contrasts noticeably with the speed of cultural evolution following its end. There is much overlap of astronomical and cultural timescales, and indeed the zodiacal cloud and Taurid meteors are visible even now, while Encke’s comet is just below naked-eye visibility. In antiquity with the complex of debris much more active, it is likely that the prime comet, lesser comets, and debris were regularly visible in the zodiac, and associated with fierce annual fireball showers and occasional impacts.

In seeking evidence of the ancient turbulent sky, we should not necessarily expect descriptions, perhaps four or five thousand years old, to be given in modern scientific terms. We do not seek comets tracking along the zodiac but gods wandering along a celestial river; rather than evanescent patches of light we should seek temporary celestial islands; rather than fireball swarms and a Tuguska impact we expect celestial thunderbolts hurled in anger; and in tales of the world’s end, we should be alert for indications that celestial catastrophe came specifically out of the constellation Taurus the Bull, or in more remote epochs, because of the evolution of the meteor orbits, out of the neighbouring constellation Aries the Ram.

Fred Hoyle and Chandra Wickramasinghe