The Halos of Vanished Civilizations

3 December 2012


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What are the consequences from a cosmological point of view when an industrial-technological civilization comes to an end, whether destroying itself or succumbing to outside forces? What kind of trace will a vanished industrial-technological civilization leave in the universe?

halo of a vanished civilization

An industrial-technological civilization that masters electromagnetic spectrum communications — i.e., ordinary radio and television signals — generates an expanding globe of EM signals as long as it is transmitting these signals. If an industrial-technological civilization that has been transmitting EM signals comes to an end, these signals cease to be generated, and the expanding globe of EM signals tapers off to silence at the interior of this globe, which means that there will be an expanding sphere of weakening EM signals. The thickness of this three-dimensional halo in light years will correspond to the age in years of the now-vanished industrial-technological civilization.

If precise measurements of the EM halo were possible, and its exact curvature could be determined, it would be possible to extrapolate the original source of the signal. Once the curvature of the halo has been determined, and therefore also the source, the measurement of the distance from the source to the inner boundary of the halo to the source in light years will yield the number of years that have elapsed since the end of the industrial-technological civilization in question.

While such signals would be very faint, and largely lost in the background radio noise of the universe, we cannot discount the possibility that advanced detection technology of the future might reveal such EM structures. The universe might contain these ghostly structures as a sequence of overlapping bubbles of EM radiation that describe the past structure of industrial-technological civilization in the universe.

It has been said that astronomy is a form of time travel, and the farther we look from Earth, the farther back we see in time. (This is called “look back time.”) Thus we can think of astronomy as a kind of luminous archaeology. Another way to think of this is that the sky reveals a kind of luminous stratigraphy. The EM halos of vanished civilizations would also admit of a certain stratigraphy, since these halos would possess a definite structure.

The outermost stratigraphic layer of an EM halo would likely consist of the simplest kind of high energy radio signals without any kind of subtle modulation of the signal — like Morse code transmitted by radio, rather than vocal modulation. This would be followed, deeper within the EM halo, by analog radio modulation corresponding to spoken language. Next within the EM halo would be analogue television signals, and then digital television signals and data signals of the sort that would be transmitted by the radio link for the internet.

This, at least, is the approximate structure of Earth’s expanding EM halo, and if our civilization destroys itself (or is destroyed) in the near future, our EM halo would be approximately 100 light years thick. The longer we last, the thicker our EM halo.

An EM halo may drop off as an industrial-technological civilization makes the transition from openly radiated EM signals to the pervasive use of fiber optic cables, but if that civilization begins to expand within its solar system, and possesses numerous settlements in EM contact with each other (as I described in Cyberspace and Outer Space), then the halo will reflect these developments — this is further historical structure layered into the EM stratigraphy of the halo.

Given that the structure of a large EM halo would consist mostly of space empty of intelligent EM signals, much of the structure of these halos would be void. It is entirely possible that Earth at present lies within the void of an EM halo that both began and ceased to transmit prior to our ability to detect such signals.

EM halo 1

In the event of human exploration of the cosmos, as we move outward within a possible void within a halo, it is possible that our first contact with a xenomorphic exocivilization will take the form of encountering the inner boundary of an EM halo, which as we pass through it, will reveal in reverse order the development of that civilization, beginning with its destruction and ending with its emergence.

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EM halo 2

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A revised, updated, and expanded version of this post is available at The Halos of Vanished Civilizations: Revised, Updated, and Expanded. A spoken word version of this updated formulation is available at Burst 9 — The Halos of Vanished Civilizations.

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Grand Strategy Annex

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