Реферат: Comets And Their Impact On Earth Essay
, Research Paper
English 111, Professor Ryan Barbour
10 December 1997
Meteors and Comets and Their Impact on Our Planet
How much do we know about our planet and its natural history? Why did the great dinosaurs disappear? All of the answers are now starting to come to light. Scientist have speculated that Earth?s history and evolution may have been more violent than we first thought. If you can, image a large chunk of rock hurtling through space heading toward Earth on a collision course and watching it come through the atmosphere. You are one step closer to understanding the extinction of the dinosaurs. In outer space, there are billions of meteors and comets, with the majority of them existing in the main belt between Mars and Jupiter. These chunks of rock are hurtling their way through space, and about every ten-billion years, one very large one hits the Earth. Such a doomsday asteroid could severely disrupt life on Earth, not only for humanity, but for the other species of plants, fish, birds, and animals.
Since we have known that dinosaurs once roamed this planet, we have asked where they went and why they suddenly passed away. Scientists have come up with the hypothesis that dinosaurs were killed by the repercussions of a massive meteor?s hitting the planet. Jon Erickson supports this idea in his book Target Earth when he adds, “The gigantic collision was so devastating that it killed three-quarters of all known species, including the dinosaurs” (148). They found that this great amount of matter hitting the earth at three times the speed of sound produced a plum cloud that enshrouded the planet with dust. This dust didn?t allow any sunlight to reach the surface of Earth. As a result, the plants had no way to grow since they were not able to photosynthesize. This produced a reaction that dismantled the food chain of the planet. The herbivores, without any plants to eat, died off. Then the carnivores died without the meat of the herbivores to support them. The only animals that were left were small and much like the mouse. Mammals then inherited the Earth from the dinosaurs. One can say that the meek inherited the Earth from the strong through this process of destruction.
When a meteor the size of a small town hits the planet, the Earth goes into a state of chaotic destruction. The Earth begins to ring like a bell and 80 percent of the population becomes permanently hard of hearing. Jon Erickson depicts what would happen when a large asteroid collides with earth, “It sets the planet ringing like a giant bell. The Jarring could induce strong earthquakes and powerful volcanic eruptions. The impact could cause the Earth?s magnetic field to flip over. A slight shift in the Earth?s axis can throw us into a ice age” (71). Whatever was at the epicenter of impact would be destroyed without a trace left of its prior existence. Then a shock wave would travel across the Earth, and everyone would hear and feel that impact of the meteor. Next, rocks that had been thrown into the air would begin to land as far as 6,000 miles away from the epicenter. The rocks would be on fire due to the heat of the explosion and their reentry into the atmosphere. Buildings would be destroyed by the projectiles that landed on them. Fires would consume what the falling debris did not destroy. People would panic, and order as we know it would be put to an end. Volcanoes would begin to erupt due to the stress put on the continental plates, and sulfur would spill into the air. If a comet or a meteor landed in the ocean, upon impact, “The comet would produce a conical shaped curtain of water, splashing billions of tons of seawater high into the atmosphere” (Erickson 77). The atmosphere would be so full of water that clouds would form over the entire planet. The clouds would be similar to thunderstorm clouds. The thick clouds would throw Earth into darkness. For those who survived the beginning of the madness, there would be something similar to a nuclear winter to look forward to. Needless to say, not many people would survive the famine and the winter to follow. These events have the potential to shift nature?s course and even to destroy the entire planet?s ability to possess life. The hypothesis that the scientists came up with was that small mammals survived the apocalypse and become the heirs of the world.
What are the possibilities of a celestial body hitting our planet? William R. Newcott tries to make clearer the chances of Earth?s being hit by a celestial body in National Geographic?s article, “The Age of Comets” when he states,
Imagine yourself atop the Empire State Building with the world?s most powerful bowling-ball cannon, capable of reaching the general vicinity of Washington, D.C. You are randomly firing bowling balls as a lone Volkswagen bug circles the Washington Beltway. It is not likely that you will hit that Beetle anytime soon, but one of these days, one of these millennia, you will inevitably crush one vintage compact car (105-106).
We live in a cosmic shooting gallery, yet during our lifetime, there?s roughly a 1-in-10,000 chance that Earth will be hit by something big enough to wipe out crops and humankind worldwide. Carl Sagan and Ann Druyan remark in their book Comet that, “We may never have to face such calamities, but it would be suicidally foolish to ignore the possibilities that a comet may hit our planet” (338). Out in space, there may be one comet with its sights set on us. The question now is when will it hit, and how can we stop it?
First we need to consider how we will detect this doomsday comet. We must have a detection system in place around the trajectory of our planet?s orbit. This detection system would need to be backed up by independent astronomers who look deep out into space. These independent astronomers have always be the prime people to find new comets. For example, Shoemaker-Levy 9 was discovered by two amateur astronomers who happened to be taking pictures of the night sky. After we have detected the celestial object, we should try to knock it off its course. This can be done simply by speeding up the comet, or buy slowing it down. Thus the comet would pass before Earth?s orbit or after Earth?s orbit. In principle, to shove an asteroid onto a different trajectory is a simpler matter. Donald Cox explains in his book, Doomsday Asteroid, the formula to deflect an moving object away from us when he states, “A rule of thumb in interplanetary navigation is that the amount you can steer your probe toward or away from your destination is the product of the mid-course correction velocity you apply multiplied by the time remaining before you arrive at your destination” (149). Another means to deflect a celestial object would be to hit it with a nuclear missile. This is simpler said then done. The number of hydrogen bombs needed to vaporize an object, even a kilometer in diameter, which is about 3/5 of a mile, would exceed the number of hydrogen bombs ever made! Also, hydrogen and nuclear bombs react differently in space than they do on Earth. Thus, we can rule this option out.
Comets have hit planets in our solar system during our life time. For Example, Shoemaker-Levy 9 was a comet that had been pulled into Jupiter?s orbit by its massive amount of gravity. The gravity of Jupiter fragmented the comet. The fragments then began to plummet into Jupiter at 60 kilometers a second, which is about 36 miles a second. The energy that was released approached the equivalent of 100,000 megatons. It produced a plum cloud that was about the size of the Earth, and that lasted for a month. The fact that a comet hit Jupiter in our lifetime, is evidence that it too can happen to us. Carl Sagan states this fact when he says, “We see that comets can hit the nearby Jupiter during our lifetimes. And we know that they have hit worlds throughout the solar system during its entire history” (comet 279). Tunguska also was one such place where a comet did hit the earth.
We are left with a lot of unanswered questions. How will we confront this threat? Will we be able to find this doomsday comet in time? We now know that such a doomsday asteroid did severely disrupt life on Earth millions of years ago, but without this disruption, humanity may have never evolved. This makes the comet both creator and destroyer of life on our planet. We as humans will continue to look at comets and meteors with the same inquisitiveness all generations before had. Their beauty is truly heavenly, yet we most not forget the power that these comets posses to destroy our world. Carl Sagan points out this fact when he mentions, “There is something unnerving about these countless lives being snuffed out, their ancestral line rendered meaningless. Naturally, we wonder if we may be next” (268).
Cox, Donald. and James Chester. Doomsday Asteroid can we Survive? New York: Prometheas Books, 1996.
Erickson, Jon. Target Earth Asteroids Collisions Past and Future. PA: Tab Books, 1997.
Newcott, William. “The Age of Comets”. National Geographic. December 1997: 96-109.
Sagan, Carl and Ann Drayan. Comet. New York: Ballantine Books, 1997.