Doomsday Comet?

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woensdag 14 januari 2009



With the passing of the New Year I invariably get e-mails asking about nothing less than the End of the World. We already survived the Y2K soothsayers. But to some people, the end is still right around the corner, as predicted from ancient writings, biblical and otherwise.

By far the so-called prophecies of the 16th century French druggie, er, druggist, Nostradamus are the biggest intellectual fraud when it comes to second-guessing the future (second only to biblical numerologists like radio evangelist Harold Camping who keeps listeners' attention by telling them that the Earth will literally go up in a ball of flames on October 21, 2011).

The latest Nostradamus-driven hysteria is that a comet is going to hit Earth on December 21, 2012. This is somehow entangled in interpritations of the Mayan Calendar which predict a comet collision, grand astronomical alignment, or some other cosmic makeover will happen to Earth on Dec. 23, 2012 (Is Dr. Seus' Grinch part of this conspiracy?)

I recently received an ominous e-mail from a Mayan calendar disciple: “The Mayan long calendar predicts 2012 to be the date the gravity of the planet Venus negatively affects the moon's lunar trajectory and causes disruptions in the weather patterns on the planet Earth. Known only as, and exacerbated by Global Warming. We need to re-engineer the moon's orbit back to a position agreeable with life on earth. This should be the sole focus of Global Warming talks and endeavors.”

Suffice to say that Venus’ gravitational pull on the moon is infinitesimal compared to Earth's pull. For all practicality both planets are nearly the same mass. But Venus, even at its closest approach to the moon, is 140 times farther away from the moon than the Earth is. Consequently its gravitational pull on the moon is nearly 1/20,000th that of Earth's. Astronomy 101 students can calculate this, without the need of the Mayan calendar.

In light of these doomsday predictions I was bemused to see that a team of scientist is reporting that our remote ancestor of 12,900 B.C. may have had to face global cooling --rather than global warming -- as a result of a comet collision with Earth. I doubt that if the Mayans, Mr. Camping, or Nostradamus had lived before this event they would have predicted it.

Possibly the earliest Paleo-Indian inhabitants of North America, called the Clovis people, abruptly vanished. Many of the largest animals including mastodons, saber-toothed cats, ground sloths and giant armadillos went extinct.

Climate change has long been the culprit for the extinctions. Nearly 13,000 years ago the planet's emergence from the last Ice Age came to a halt, reverting abruptly to freezing conditions for another 1,500 years. Nothing of the size, extent, or rapidity of this period of abrupt climate change has been experienced since then, say experts.

The debated smoking gun evidence for a cosmic collision comes from microscopic diamonds, called nanodiamonds. They are found in a rich sedimentary soil called a "black mat,” that dates back to nearly 13,000 years. Beneath the sooty layer fossils of animals are abundant. But just above that layer, the fossils disappear, along with arrowheads and other artifacts from the Clovis culture.

The heat and pressure from explosions in the atmosphere would have transformed carbon on our planet's surface into the tiny diamonds, say researchers James P. Kennett of the University of California at Santa Barbara and Douglas J. Kennett of the University of Oregon.

Their idea is that a comet broke into pieces while approaching Earth. In what must have been the mother-of-all fireworks spectacles, fragments burned up and exploded over a broad area of North America. There are no telltale craters. The researchers describe several Tunguska type explosions going off in sequence, carpet-bombing North America. Each blast would have lit up the sky, brighter than the sun.

Dust from the explosions, combined with soot from continent-wide wildfires could have risen into the atmosphere, blocking sunlight to bring on a nuclear winter. With vast portions of the landscape burned, even those large animals that survived the sky bombardment would have died off as the food chain collapsed.

The idea of a comet breaking up is not conjecture. The so-called sun-grazing comets do often disintegrate into football-field sized pieces. In the early 1990s astronomers followed the breakup of comet Shoemaker-Levy 9 (SL9) by Jupiter’s gravitational pull. A total of 23 pieces of the comet slammed into Jupiter in July 1994. So-called crater chains are seen on the icy outer moons. These too must have been laid down by a string of comet pieces.

But a veteran of the SL9 event, planetary astronomer Heidi Hammel, recently told me that the idea of comet pieces barreling into North America all at once is pretty implausible. Impacts would have been scattered across Earth as our planet rotated, as we saw in the the SL9 bombardment.

So the bottom line is that no ancient calendar, scripture or soothsayer can predict what the cosmic roll of dice will deal us. And, evidence for past armegeddons can be pretty dicey too. Like a good insurance actuator, we can only look at probabilities, and even these are no all inclusive.

Bron: discovery

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