Read the following passage and think of the scientific abilities illustrated in
ID: 3281229 • Letter: R
Question
Read the following passage and think of the scientific abilities illustrated in it. Radio-carbon dating is a method of obtaining age estimates on organic materials which has been used to date samples as old as 50,000 years. The method has provided age determinations in archeology, geology, geophysics, and other branches of science. Radiocarbon determinations can be obtained on wood, charcoal, marine and freshwater shell, bone and antler, and peat and organic-bearing sediments. They can also be obtained from carbonate deposits and carbonates in ocean, lake and groundwater sources. Using radiocarbon dating, archaeologists have been able to obtain a global perspective on the timing of major prehistoric events such as the development of agriculture in various parts of the world. Therefore radiocarbon dating has had the most profound impact in archeological research and particularly in prehistoric studies, but extremely significant contributions have also been made in hydrology and oceanography. In September of 1991 a German couple, while hiking through the Alps bordering western Austria and northern Italy southwest of Innsbruck, inadvertently came upon what might be considered the single most remarkable archaeological find of European prehistory. Summer melting of the Similaun Glacier had exposed a frozen man's head and shoulders. At first he was thought to be another hiker who had met with a fatal accident, but the artifacts accompanying the corpse soon dispelled this presupposition. The body of the Ice Man was almost fully preserved, and scientists begun to study his anatomy in detail. He stood about five feet two inches tall and weighed about 110 pounds. Although his age at time of death was initially estimated at twenty-five to forty years, subsequent analysis of bone and blood vessels has shown him to have been forty to fifty years old and beginning to suffer from degenerative arthritis. He had brownish black hair, wore a beard, and would easily blend into the local Alpine population today if put in contemporary dress. The hair on his head is only three and a half inches long, demonstrating that the people of his culture regularly cut their hair. But perhaps the most informative aspects of this discovery pertain to his clothing and other artifacts. Unlike the grave goods uncovered from ancient burials, which were placed with the dead according to the prevailing funerary customs and religious beliefs, the Ice Man was not formally buried but died with all his regular gear about him, and its remarkable state of preservation offers unique insights into the living conditions and technology of his culture. He wore leather boots bound around his legs with thongs and stuffed with straw for insulation against the cold. He was clad in a fur-lined coat composed of deer, chamois, and ibex skin stitched together, and over this he wore a cape of woven grass similar to those worn by local Tyrolean shepherds as late as the early twentieth century. A disk-shaped stone may have been worn around his neck as an amulet. He had with him a bow, fourteen arrow shafts, and what is now the world's oldest known quiver, made of deerskin. The arrows are fitted with feathers at an angle so as to impart spin for greater stability and accuracy. His bow measures six feet in length and is made of yew, the best wood available in Europe for bow making, the same as that used to make the famous English long bow. His bow, however, had not yet been notched and fitted with a string, suggesting that the Ice Man had only recently obtained the wood from a tree. He also had a bone needle, a small flint knife fitted with a handle of ash wood, a copper axe, and a small tool of deer antler that was probably used for sharpening flint blades and arrowheads. The flint knife was carried in a delicately woven grass sheath. Pieces of charcoal contained in a grass packet were used for making a fire. His equipment was carried in a backpack made of wood and bark. When did this man live and how do we know it? Few samples of his bones and gear were taken and analyzed using the Carbon-14 method. Carbon-14 dating indicates that this man lived around 3500-3000 b.c., which makes him approximately as old as the earliest civilizations of Mesopotamia and Egypt. His equipment, in particular the characteristics of his copper axe, supports this age estimation. During its lifetime, any organism continually replenishes its supply of carbon just by breathing and eating. Carbon (C) has three naturally occurring isotopes. Both C-12 and C-13 are stable, but C-14 decays with a half-life of approximately 5,730 years. These isotopes are present in the atmosphere and in living organisms in the following amounts C-12 - 98.89%, C-13 - 1.11% and C-14 - 0.0000000001%. Naturally occurring C-14 is produced as a secondary effect of cosmic-ray bombardment of nitrogen-14 in the upper atmosphere. After the C-14 is generated, it oxidizes rapidly forming CO2. Then it enters the Earth's plants and animals through photosynthesis and the food chain. After an organism dies, Carbon-14 continues to decay without being replaced. The decay is constant and spontaneous. To measure the amount of radiocarbon left in organic remnants, scientists burn a small piece to convert it into carbon dioxide gas. Radiation counters are used to detect the electrons given off by decaying C-14 as it turns into nitrogen. The amount of C-14 is compared to the amount of C-12, the stable form of carbon, to determine how much radiocarbon has decayed, therefore, dating the fossil. Decay equation: A = A0 * 2(-t/k) "A" is the present amount of the radioactive isotope; "A0" is the original amount of the radioactive isotope that is calculated from the amount of C-12; "t" is the time it takes to reduce the original amount of the isotope to the present amount, and "k" is the half-life of the isotope. The text above has been modified from Gary Forsythe's "A Critical History of Early Rome:
From Prehistory to the First Punic War" (chapter one) and from the NDT Resource Center website: www.nde-ed.org. After you have read the passage, answer the following questions:
1) The passage relates the solution of a problem, which problem?
2) What knowledge did the researchers use to solve the problem?
3) What type of experiment (observation, testing or application) was conducted with the iceman? How do you know?
4) How did the researchers evaluate (decide it was reliable) the result they got from the carbon dating experiment?
5) Did the researchers apply any mathematical procedure to solve the problem? 6) If the rubrics were being used to evaluate the report's estimation of the iceman's age, which rubrics would be used? (A1, D3, etc.)
Explanation / Answer
1) The passage relates to the confirmatory solution of finding age of any unknown object or organism using the process of radiocarbon dating.
2) In order to get confirmation about the age of the ice man, the researchers used their knowledge about radio carbon dating. This is based on the fact that C-14, one of the isotopes of carbon, is found in in living organisms (in 0.0000000001%) and has a known half-life of about 5730 years. It generally enters the body of the organism through food chain. After an organism dies, Carbon-14 continues to decay without being replaced. The decay is constant and spontaneous. To measure the amount of radiocarbon left in organic remnants, scientists burn a small piece to convert it into carbon dioxide gas. Radiation counters are used to detect the electrons given off by decaying C-14 as it turns into nitrogen. The amount of C-14 is compared to the amount of C-12, the stable form of carbon, to determine how much radiocarbon has decayed, therefore, dating the age of the organism.
3) Initially, the anatomy of the iceman was studied in detail. This gave the researchers a preliminary knowledge about the height, weight, hair colour and his age at the time of death.
Secondly, his belongings and clothing was observed carefully and from that information the researchers tried to relate his origin.
Lastly, few samples of his bones and gear were taken and analyzed using the Carbon-14 method. This process indicated that this man lived around 3500-3000 b.c., which revealed that he was as old as the earliest civilizations of Mesopotamia and Egypt.
4) The carbon dating experiment revealed that this man lived around 3500-3000 b.c. His equipment, in particular the characteristics of his copper axe, supports this age estimation as that time marks the begining of copper age in history.
5) The researchers used the decay equation A = A0 * 2(-t/k) where "A" is the present amount of the radioactive isotope; "A0" is the original amount of the radioactive isotope that is calculated from the amount of C-12; "t" is the time it takes to reduce the original amount of the isotope to the present amount, and "k" is the half-life of the isotope.
6) Details about the rubrics is not mentioned in the question.
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