arguing for an


This article, (METEOR DEFENSE, by Bob Kobres) first appeared in WHOLE EARTH REVIEW #56 (Fall 1987) pp. 70-73.

IN HIS ARTICLE "A Gaian Politics" (WER #53, p.4), historian William Irwin Thompson asks: "What would be the slightest and subtlest of moves that could transform our present political environment from one of terror to a life-centered polity of compassion?" He goes on to say that the martial arts teach us to appraise the situation as given and look for ways to redirect the energies manifested toward positive goals. As an example, Thompson suggests that the Strategic Defense Initiative (SDI) could be transformed into a transnational program for the exploration of space.

But would the mysteries of Mars provide sufficient cement to bind opposing parties long enough for their mutual paranoia to wane? Thompson laments that, even if desired, transformation is difficult for a nation with an economy built around preparation for war. The military component must be reduced slowly as employment is shifted to other areas--a task next to impossible without government subsidies. The problem, he states, "is that citizens and politicians will only vote for subsidies under threat, and so there always has to be a threat from the enemy or the environment to mobilize a society."

If we need an external threat to bring us together, we need only look toward the stars. It's a sobering thought when one realizes that a stony object only 350 meters in diameter colliding with Earth at what is considered to be an average impact velocity of 25 km per second would liberate the energy equivalent of 5,000 megatons TNT within our environment. In other words, a hunk of rock that could be nestled into a modern sports arena could release an amount of energy 250,000 times as great as the 20-kiloton nuclear device that destroyed Hiroshima. This is a definite "nuclear winter" level--5,000 megatons is often used as a typical exchange figure in nuclear war scenarios.

An event of this magnitude is not in the same class as the hypothetical 100,000,000-megaton event that polished off the dinosaurs, but it would most certainly throw civilization into a dark age. Our climate would be seriously perturbed; growing crops out in the open would be next to impossible for the first year and frustrating for years to come. Famine would be global. All in all, it would not be unlike enduring a nuclear war; the ozone layer would be depleted, disease would be rampant, governments would collapse.

British astronomers Victor Clube and Bill Napier, in their The Cosmic Serpent (1982), give 1900 years as a typical interval for a collision of this magnitude. These astronomers work at the Royal Observatory in Edinburgh. Their estimate carries with it two important implications. One is that since we can be pretty sure no event of this magnitude has occurred during the historical period (the last 2,500 years), we are statistically overdue for such a wallop. The other implication is that we should not be surprised to find that earlier civilizations have been brought down by cosmic collision. We must no longer glibly assume that the ancients were talking through their hats when their writings spoke of fire coming down from heaven and destroying whole cities.

The Tunguska object that hit Russia in 1908 could have easily wiped out a city. In fact, if the Earth had been advanced in its rotation by about 71 degrees (4 hours and 45 minutes) the object would have vented its 15- to 30-megaton blast over Leningrad (then St. Petersburg). Considering that the actual downward-directed blast scorched and leveled 2,000 square kilometers (700 sq. mi.) of dense Siberian forest, cremating the wildlife within, and produced a shock wave that traveled completely around the world twice, it is safe to assume that few if any of the city's two million inhabitants would have survived. Such an event would have changed recent history.

Plato was aware of cosmic collisions and held them responsible for losses of history. In his Timaeus, Plato states that the myth of Phaethon (son of the Sun who burns up the natures of the Earth) is in reality true as it expresses the mutations of the bodies revolving about the Earth and indicates that, at infrequent intervals, a destruction of terrestrial natures ensues from the devastations of fire.

Clube and Napier have developed a very credible scenario that supports Plato's contention. They postulate that around 5,000 years ago a large comet, perhaps 20 km in diameter, was perturbed by Jupiter into a short period orbit which intersected our own planet's orbit. A comet of this size will inevitably break up, leaving in its path debris of varying sizes and shapes. Since this comet was crossing the orbit of Earth, at least once a year our planet would have to careen its way through this debris path producing a spectacular meteor shower about the same time every year. Most of the larger comet pieces (100 to 1,000 meters across) would be found not too far away from the original comet at first, but the force--be it rotation or gas pressure--that separated them initially would still be with them, so they would continue to drift away from the main berg. From the standpoint of the Earth, what had been a rifle bullet became a load of buckshot. Clube and Napier speculate that while streaking through this dense swarm close to the comet, the Earth could have encountered, in the course of half an hour, thirty impacts in the range of 10 to 100 megatons with perhaps a few in excess of this!

By combining astronomical facts with archaeological evidence, such as ancient calendars and astronomically aligned megalithic structures, Clube and Napier further speculate that the object responsible for this mischief was the progenitor of the comet Encke. Kenneth Brecher, an astrophysicist at Boston University, sees a link between comet Encke, the Tunguska event of June 30, 1908, and the June 25, 1178 impact on the Moon reported by the monk Gervase of Canterbury. This lunar impact is thought to have produced a crater (Giordano Bruno) 20 kilometers in diameter! To account for both these energetic events occurring on almost the same day of the year, Brecher postulates that a large piece of comet Encke broke away prior to 1178, producing a swarm of objects, some of which could be a kilometer across. He believes this swarm will be entering the Earth-Moon system again in the year 2042.

Cosmic debris has a size distribution somewhat like pebbles on a beach--the small outnumber the large Currently the population of Earth-orbit-crossing asteroids a kilometer or larger in diameter is estimated to be around 2,000. If we go down in size to our 350-meter-across civilization cruncher, this number would at least double, and if all football-field-size city smashers such as the Tunguska object were included, the population would jump into the tens-of-thousands range. Including comets, less than 100 Earth-orbit-crossing objects (EOCOs) have been discovered to date. The limitations of a telescope looking through an ocean of air favors the detection of the larger objects, so most of the EOCOs detected so far have a diameter of a kilometer or more.

Our vast ignorance with respect to the whereabouts of these objects means, in the words of active EOCO hunter-geologist Eugene Shoemaker, "until we have tracked all of them, something could sneak up on us." Tracking all EOCOs is going to take some time. Planetary scientist Eleanor Helin and colleagues have found 20 of the known EOCOs; this represents 13 years of seeking. Even if improved equipment allows a discovery rate of 20 EOCOs per year we are speaking of perhaps 100 years just to locate the objects a kilometer or more across. The point is this: because there is at present absolutely no way to predict when the next major impact will occur, we are fools if we do not effect a defense against these objects as soon as possible.

Eugene R. Mallove, in his outstanding article "The Bombarded Earth" (Technology Review, July 1985), makes the point that "a major difference between the threat from asteroids and that from nuclear warfare is that asteroid impacts will inevitably occur unless action is taken to prevent them. The trajectories of heavenly bodies leave no room for obscure calculations regarding the balance of nuclear terror." Unless we as a species truly have a death wish, the very presence of these Earth-orbit-crossing objects combined with our growing understanding of their destructive potential and the effect they have had upon our own history should be enough to bring forth a significant change within Gaia--at minimum a transformation of the nationalistic SDI to a globally cooperative Earth Defense Initiative (EDI), a transition which would redirect, without negative economic effects, the efforts and talents of many, if not most, who are currently involved in space weapons research and development.

We must put the ghost of past world wars to rest; should such warfare recrudesce, civilization in the northern hemisphere will surely cease. The strongest force pushing us toward such an unwanted recurrence is the fear of a breakthrough in weapon system technology. It is this fear combined with economic profitability that allows and encourages continued weapon system research and development. Historically such research and development has progressively reduced the time for human consideration during a time of crisis. This current project, SDI, threatens to reduce time for thought even more. A major purpose of EDI is to redirect this weapon research and development in an economically beneficial manner, toward a necessary and positive goal--protection of our environment. There is currently no technology available for tracking, following, and deflecting an incoming meteor or comet. The pieces of the technology are there, but they need to be put together with this purpose in mind. Attainment of this goal demands long-term active cooperation between East and West. Such cooperation is essential due to the fact that space-based nuclear explosives are the only tools that would in all cases be capable of altering the orbit of a large asteroid or comet. Hopefully, after the decades of intense, highly visible, active cooperation necessary to accomplish this project, fear of a weapon system breakthrough will have vanished.

Space is no place for weapons! Our access to it is rather an opportunity to eliminate a root cause of warfare--contention over the control of nonrenewable resources. The doomsday machines in place on this planet serve only one purpose--they maintain the status quo. By cooperatively developing an Earth defense system, the superpowers will have done far more than ensure a collision-free future; they will have constructed an infrastructure that allows the transformation of these cosmic threats into vast supplies of currently limited materials, raw materials which will no longer have to be gouged from Earth or refined at the expense of environmental quality.

The decision to protect our environment from significant random impacts as soon as we possibly can should not be argued against on the basis of static probability statistics. These numbers vary widely between authorities and have changed dramatically over the past few years; they give us only a crude estimate of the average frequency of such events. The odds against a damaging collision between Earth and an Earth-orbit-crossing object tell us nothing as to when we should expect the next event to occur. Our decision to develop an Earth defense system must be based upon the predictable consequences of an abrupt encounter of the worst kind.

This threat could very well be our most powerful defense against prevailing maniacal forces within the military-industrial juggernaut. By the simple act of petitioning (with persistence) our government to protect us from cosmic calamity, we may, in true aikido fashion, throw off the balance of this myopic military-industrial Goliath just enough to send it upon a new, constructive path--a path that leads away from this dark cloud which looms so heavily in the minds of us all.


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