Period: 8During the first part of class we talked about Isotopes andcarbon dating. This subject caught my attention unlike other lessons, so Idecided to do my report on this topic. It is not very controversial, theonly controversy being if it is accurate or not. Carbon dating iscontroversial in that is shares some of the fundamental assumptionsinherent to all Radiometric Dating techniques. In order for Carbon Datingto have any value, Carbon-14, produced in our outer atmosphere as Nitrogen-14 and changed into radioactive Carbon-14 by cosmic-ray bombardment, andmust be at equilibrium in our atmosphere.
In other words, the productionrate must be equal to the decay rate. Therefore, the question I pose isthis; is carbon dating an effective way of telling the date of artifacts?The first thing I will discuss is how carbon dating works. Carbon-14is the radioactive version of Carbon. Radiation from the sun strikes theatmosphere of the earth all day long. This energy produces radioactiveCarbon-14.
This radioactive Carbon-14 slowly decays into normal, stableCarbon-12. Laboratory testing has shown that about half of the Carbon-14molecules will decay in 5730 years. After another 5730 years half of theremaining Carbon-14 will decay, leaving only of the original Carbon-14. It goes from to to 1/8, ect. In theory it would never totallydisappear, but after about 5 half lives the difference is not measurablewith any degree of accuracy.Order now
This is why most people say that carbon datingis only good for objects less than 30,000 years old. Since sunlight causes the formation of Carbon-14 in the atmosphere,and normal radioactive decay takes it out, there must be a point where theformation rate and the decay rate equalize. This is called the point ofequilibrium. Let me illustrate; if you were trying to fill a barrel withwater but there were holes drilled up the side of the barrel, as you filledthe barrel it would began leaking out the holes. At some point you would beputting water in and water would be leaking out at the same rate. You willnot be able to fill the barrel pas this point.
In the same way Carbon-14 isbeing formed and is decaying out simultaneously. A freshly created earthwould require about 30,000 years for the amount of Carbon-14 in theatmosphere to reach this point of equilibrium because it would leak out asit is being filled. Tests indicate that the earth has yet to reachequilibrium. This would mean that the earth is not yet 30,000 years old.
This also means that plants and animals that lived in the past had lessCarbon-14 in them than they do today. This one fact totally upsets dataobtained by Carbon-14 dating. Yet another example is a candle you find burning in a room. You couldmeasure the present height of the candle (say, seven inches) and the rateof burn (say, an inch per hour). In order to find the length of time sincethe candle was lit we would be forced to make some assumptions.
We wouldobviously have to assume that the candle has always burned at the samerate, and the initial height of the candle. The answer changes based on theassumptions. Similarly, scientists do not know that the Carbon-14 decayrate has been constant. They do not know that the amount of Carbon-14 inthe atmosphere is constant.
Present testing shows the amount of Carbon-14in the atmosphere has been increasing ever since it was first measured inthe 1950’s. This may be tied in to the declining strength of the magneticfield, but this has not yet been proven. This dating technique assumes that Carbon-14 has reached equilibrium. There is more Carbon-14 in our atmosphere today then there was at any timein the past. Thus, Carbon Dating is controversial.
If there’s more Carbon-14 in the atmosphere today than there was 50 years ago, then an animal thatdied 100 years ago would test at an artificially higher age. Many experiments have been done in attempts to change radioactivedecay rates, but these experiments have failed to produce any significantchanges. We have found that decay constants are the same at a temperatureof 2000 degrees Celsius or at a temperature of 186 degrees Celsius and arethe same in a vacuum or under pressure of several thousand atmospheres.Measurements of decay rates under differing gravitational and magneticfields also have provided negative