Isegoria

The Sky Is Falling, as it always has, but far more chunks may hit the earth than we realized:

Breakthrough ideas have a way of seeming obvious in retro­spect, and about a decade ago, a Columbia University geophysicist named Dallas Abbott had a breakthrough idea. She had been pondering the craters left by comets and asteroids that smashed into Earth. Geologists had counted them and concluded that space strikes are rare events and had occurred mainly during the era of primordial mists. But, Abbott realized, this deduction was based on the number of craters found on land—and because 70 percent of Earth’s surface is water, wouldn’t most space objects hit the sea? So she began searching for underwater craters caused by impacts rather than by other forces, such as volcanoes. What she has found is spine-chilling: evidence that several enormous asteroids or comets have slammed into our planet quite recently, in geologic terms. If Abbott is right, then you may be here today, reading this magazine, only because by sheer chance those objects struck the ocean rather than land.

Abbott believes that a space object about 300 meters in diameter hit the Gulf of Carpentaria, north of Australia, in 536 A.D. An object that size, striking at up to 50,000 miles per hour, could release as much energy as 1,000 nuclear bombs. Debris, dust, and gases thrown into the atmosphere by the impact would have blocked sunlight, temporarily cooling the planet—and indeed, contemporaneous accounts describe dim skies, cold summers, and poor harvests in 536 and 537. “A most dread portent took place,” the Byzantine historian Procopius wrote of 536; the sun “gave forth its light without brightness.” Frost reportedly covered China in the summertime. Still, the harm was mitigated by the ocean impact. When a space object strikes land, it kicks up more dust and debris, increasing the global-cooling effect; at the same time, the combination of shock waves and extreme heating at the point of impact generates nitric and nitrous acids, producing rain as corrosive as battery acid. If the Gulf of Carpentaria object were to strike Miami today, most of the city would be leveled, and the atmospheric effects could trigger crop failures around the world.

What’s more, the Gulf of Carpentaria object was a skipping stone compared with an object that Abbott thinks whammed into the Indian Ocean near Madagascar some 4,800 years ago, or about 2,800 B.C. Researchers generally assume that a space object a kilometer or more across would cause significant global harm: widespread destruction, severe acid rain, and dust storms that would darken the world’s skies for decades. The object that hit the Indian Ocean was three to five kilometers across, Abbott believes, and caused a tsunami in the Pacific 600 feet high—many times higher than the 2004 tsunami that struck Southeast Asia. Ancient texts such as Genesis and the Epic of Gilgamesh support her conjecture, describing an unspeakable planetary flood in roughly the same time period. If the Indian Ocean object were to hit the sea now, many of the world’s coastal cities could be flattened. If it were to hit land, much of a continent would be leveled; years of winter and mass starvation would ensue.

At the start of her research, which has sparked much debate among specialists, Abbott reasoned that if colossal asteroids or comets strike the sea with about the same frequency as they strike land, then given the number of known land craters, perhaps 100 large impact craters might lie beneath the oceans. In less than a decade of searching, she and a few colleagues have already found what appear to be 14 large underwater impact sites. That they’ve found so many so rapidly is hardly reassuring.

Other scientists are making equally unsettling discoveries. Only in the past few decades have astronomers begun to search the nearby skies for objects such as asteroids and comets (for convenience, let’s call them “space rocks”). What they are finding suggests that near-Earth space rocks are more numerous than was once thought, and that their orbits may not be as stable as has been assumed. There is also reason to think that space rocks may not even need to reach Earth’s surface to cause cataclysmic damage. Our solar system appears to be a far more dangerous place than was previously believed.
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A generation ago, the standard assumption was that a dangerous object would strike Earth perhaps once in a million years. By the mid-1990s, researchers began to say that the threat was greater: perhaps a strike every 300,000 years. This winter, I asked William Ailor, an asteroid specialist at The Aerospace Corporation, a think tank for the Air Force, what he thought the risk was. Ailor’s answer: a one-in-10 chance per century of a dangerous space-object strike.

I can’t help but think of Lucifer’s Hammer and the challenge of bootstrapping society.

Michael Tomasello, co-director of the Max Planck Institute for Evolutionary Anthropology, explains how humans are unique:

[The human 2-year-olds] performed about the same as the apes on the tests that measured how well they understood the physical world of space, quantities and causality. The children performed better only on tests that measured social skills: social learning, communicating and reading the intentions of others.

But such social gifts make all the difference. Imagine a child born alone on a desert island and somehow magically kept alive. What would this child’s cognitive skills look like as an adult — with no one to teach her, no one to imitate, no pre-existing tools, no spoken or written language? She would certainly possess basic skills for dealing with the physical world, but they would not be particularly impressive. She would not invent for herself English, or Arabic numerals, or metal knives, or money. These are the products of collective cognition; they were created by human beings, in effect, putting their heads together.

When you look at apes and children in situations requiring them to put their heads together, a subtle but significant difference emerges. We have observed that children, but not chimpanzees, expect and even demand that others who have committed themselves to a joint activity stay involved and not shirk their duties. When children want to opt out of an activity, they recognize the existence of an obligation to help the group — they know that they must, in their own way, “take leave” to make amends. Humans structure their collaborative actions with joint goals and shared commitments.

Another subtle but crucial difference can be seen in communication. The great apes — chimpanzees, bonobos, gorillas and orangutans — communicate almost exclusively for the purpose of getting others to do what they want. Human infants, in addition, gesture and talk in order to share information with others — they want to be helpful. They also share their emotions and attitudes freely — as when an infant points to a passing bird for its mother and squeals with glee. This unprompted sharing of information and attitudes can be seen as a forerunner of adult gossip, which ensures that members of a group can pool their knowledge and know who is or is not behaving cooperatively. The free sharing of information also creates the possibility of pedagogy — in which adults impart information by telling and showing, and children trust and use this information with confidence. Our nearest primate relatives do not teach and learn in this manner.

Finally, human infants, but not chimpanzees, put their heads together in pretense. This seemingly useless play activity is in fact a first baby step toward the creation of distinctively human social institutions. In social institutions, participants typically endow someone or something with special powers and obligations; they create roles like president or teacher or wife. Presidents and teachers and wives operate with special powers and obligations because, and only because, we all believe and act as if they fill these roles and have these powers. Two young children pretending together that a stick is a horse have thus taken their first step on the road not just to Oz but also toward inhabiting human institutional reality.