"............Not the Mama"
RADIOMETRIC DATING (PART 2)
In almost every basic book about dinosaurs or paleontology I could find when I was little there was always the section with the picture of the clock showing that if the earth’s history was a 24-hour day, man only appeared within the last couple minutes. I’ve seen this picture so many times I’m beginning to think I have that image imprinted in my mind. But as annoying as that analogy has gotten for me it is a good example that shows just how old the earth is at 4 and a half billion years. Or at least that is how old it is according to science. Attempts have been made for hundreds of years to find out the age of the earth and none of the earlier estimates have come even close to even a billion years, not alone four and a half. Lord Kelvin performed one of the first relatively recent scientific calculations on the age of the earth in 1862 and came up with an age range of 20-400 millions years. This was the range of many of the calculations done over the next 50 years such as an age based on the contraction of the Sun at 100 million years and another based on the rate at which salt as been carried into the oceans which gives 90 million years old. But none of these turned out to be remotely accurate. The Sun does contract (extremely slowly over billions of years) but it was assumed that was the only way the Sun gave off heat. They did not know about fusion yet. The theory involving the deposition of salt is also flawed because of the absence of information we have learned since then. At the beginning of the 20th century, a new method was discovered that Lord Kelvin had not known to consider: radioactive dating.
In the last entry (I apologize for the length of time since the last entry) I described how carbon dating works and hopefully showed that it is an effective and accurate method. But carbon dating has a half-life of 5,730 years, which means that it can only date things to about 60,000 years old. After this time so much of the carbon has decayed that there is no measurable amount of carbon left. The reliability of carbon-dating even become more inaccurate as it comes closer to 60,000 years so that truly reliable dating involves measurements of less than 60,000 years. When most people argue against radiometric dating, they argue against the accuracy of carbon-dating. But what many people don’t realize is that there are over 40 different kinds of dating. Just to get an idea of all the different kinds here is a list of some of the more common elements used in radiometric dating (the numbers represent the weight of the atom):
H-3 Be-10 Na-22 Al-26 Si-32
Cl-36 Ar-39 Ca-41 Mn-53 Kr-81
I-129 Common Lead Chemical Lead
The rest show the atom before decay followed by the atom it decays into:
K-40/Ar-40 Ar-39/Ar-40 K-40/Ca-40
Rb-87/Sr-87 La-138/Ce-138 La-138/Ba-138
Sm-147/Nd-147 Lu-176/Hf-176 Re-187/Os-187
Pb-207/Pb-206 Uranium/Xenon Th-230/U-234
Pa-231/U-235 Pa-231/Th-230 U-234/U-238
U/He
Not all of these elements decay in the same way that carbon does. There are over a dozen different ways an element can decay so I will not describe them all. But most elements that decay will periodically eject some particle from its nucleus.
One of the more commonly used methods of dating involves potassium-40. It decays into rock that is 11.2% Ar-40 and 88.8% Ca-40. It is too difficult to determine the age for the Ca-40 so Ar-40 is used, which is much more reliable. The potassium has a half-life of 1.26 billion years. I should note here that while it is impossible to measure exactly one half-life of potassium-40 through direct observation, there are so many atoms in any sample that over just one year, millions upon millions of atoms decay and can be counted. Counting decays is like putting dots on a graph. Even with only two dots you can draw a straight line. Following this straight line, with all the dots somewhere along the line, you can calculate the half-life, in this case 1.26 billion years. Another element commonly used is Rubidium-87, which decays into Strontium-87 over a half-life of 49 billion years. Uranium-lead dating is one of first methods of dating discovered. It is the most interesting to me because you have different kinds, or isotopes, of Uranium in the same sample. Uranium-235 decays into lead-208 along with uranium-238 decaying into lead-206. Each has a very different half-life, 4.5 billion years for uranium-238 and 700 million years for uranium-235. The huge difference in half-lives of the isotopes makes verification of the age of a rock even more certain. Many of these elements do not directly decay into daughter rock. To make this clearer, let’s use uranium-238 as an example. While it does eventually decay into lead-206, it does so after decaying into many other elements. Just to give you an idea of what I’m talking about here is a list of elements that uranium decays into before becoming lead-206:
U-238 Th-234 Pa-234 U-234 Th-230
Ra-226 Rn-222 Po-218 At-218 Rn-218
Pb-214 Bi-214 Po-214 Tl-210 Pb-210
Bi-210 Po-210 Tl-206 Pb-206
Each stage has a different half-life that makes up the 700 million years. Some take thousands of years, but others are much shorter. The half-life of Th-234 is only 24 days and the half-life of At-218 is a miniscule 1.5 seconds.
Besides radiometric dating, there are other ways to be able date objects but I will only summarize them. One is by what is called ice cores. In areas covered by snow year-round there are differences in the snow with each season such as larger crystals in the summer, the chemistry of the ice, and dust that is deposited in the summer. Varves are another method. Among other factors, the amount of algae and pollen in sediment will cause variations among different layers laid by streams. Other methods include using coral reefs, thermoluminescence (light given off by electrons as they drop to another orbit), the changing of an electron’s spin, paleomagnetism (changes of charges in the earth’s poles over time), and dating involving the exposure of certain isotopes to cosmic rays from the sun.
Now you may be wondering why I am practically listing all these different methods to date fossils. But hopefully I have expressed the point that there are numerous methods, not just carbon-dating, which is the only one many people have heard of. Any combination of methods has been used to date any given rock. One estimate I’ve heard is that around one thousand scientific papers are written each year from hundreds of labs concerning and verifying radiometric dating. Over the 50 years that radiometric dating has been used, there has been 100,000s of papers written.
In contradiction to an earth that is billions of years old is the Creation belief that the earth is only thousands of years old. So there remain objections to the research done in radiometric dating. One argument is that the decay rate of elements is not constant, but it gradually speeds up so that when we calculate a half-life to be billions of years old it is actually only thousands of years old. But all the measurements that have been done on long-period half-lives and short-period radioactive isotopes have always been constant, never an indication that their rates change. Other objections state that processes like weathering and metamorphism (rocks undergoing very high pressures) or that there are daughter atoms in the sample or rock along with the parent atoms when the rock is first formed (it should contain only parent atoms at that time). These objections are quite valid but it is not right that all radiometric dating is false because these conditions are present. What those people who argue dating do not realize is that all these factors are already taken into consideration. Either necessary calculations are made to fix these problems or the rocks are simply thrown out. One last objection I would like to discuss is that geologists only publish those few times that radiometric dating works and ignore those times that it doesn’t. At first glance seems possible, and seriously did make me wonder at first. But when I looked into it more I saw that it takes hundreds of dollars to just date even one sample. From what I see with the costs of equipment and experimentation in undergraduate school alone, it makes very much sense that it would cost a lot of money to date just one sample. Now if only a small fraction of tests yield the results I’ve been describing, then hundreds of thousands or even millions of dollars have been wasted on dating samples. For labs that most likely done receive enough funding in order to afford to waste thousands of dollars, this seems extremely unlikely if not impossible.
The argument I have made describes my search between different arguments concerning radiometric dating. The large amounts of data show at least to me that it is much more likely that the earth is billions of years old. But the next thought in my head concerned the implication of this on Creation and on the Bible, which apparently tells a very different story. That has been the object of much hatred and arguments for over a hundred years. As it was when I was younger I have concentrated only on evolution thus far. But now there is only one more major thing I must discuss on evolution before changing gears toward something that I have been researching more recently, which are the implications that evolution has on Christianity. What I have found is different from most anything at least that I have seen argued before.
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