1. Radiometric Dating radiometric datingthe process of determining the age of rocks from the decay of their become increasingly clear that these radiometric dating techniques agree with each other http://www.asa3.org/ASA/resources/Wiens.html

Science in Christian Perspective Radiometric Dating A Christian Perspective Dr. Roger C. Wiens 941 Estates Drive, Los Alamos, NM 87544 RWiens@Prodigy.Net [A PDF version of this document is also available.] First edition 1994; revised version 2002. Radiometric datingthe process of determining the age of rocks from the decay of their radioactive elementshas been in widespread use for over half a century. There are over forty such techniques, each using a different radioactive element or a different way of measuring them. It has become increasingly clear that these radiometric dating techniques agree with each other and as a whole, present a coherent picture in which the Earth was created a very long time ago. Further evidence comes from the complete agreement between radiometric dates and other dating methods such as counting tree rings or glacier ice core layers. Many Christians have been led to distrust radiometric dating and are completely unaware of the great number of laboratory measurements that have shown these methods to be consistent. Many are also unaware that Bible-believing Christians are among those actively involved in radiometric dating. This paper describes in relatively simple terms how a number of the dating techniques work, how accurately the half-lives of the radioactive elements and the rock dates themselves are known, and how dates are checked with one another. In the process the paper refutes a number of misconceptions prevalent among Christians today. This paper is available on the web via the American Scientific Affiliation and related sites to promote greater understanding and wisdom on this issue, particularly within the Christian community.

2. Radiometric Dating radiometric dating. How do we determine the age of a rock? Relative dating Steno s Laws, etc. radiometric dating. Principles of radiometric dating. http://www.dc.peachnet.edu/~pgore/geology/geo102/radio.htm

Radiometric Dating How do we determine the age of a rock? Relative dating - Steno's Laws, etc. "A is older than B" Absolute dating Quantify the date in years. Radiometric Dating Principles of Radiometric Dating Naturally-occurring radioactive materials break down into other materials at known rates. This is known as radioactive decay Radioactive parent elements decay to stable daughter elements. Radioactivity was discovered in 1896 by Henri Becquerel. In 1905, Rutherford and Boltwood used the principle of radioactive decay to measure the age of rocks and minerals (using Uranium decaying to produce Helium. In 1907, Boltwood dated a sample of urnanite based on uranium/lead ratios. Amazingly, this was all done before isotopes were known, and before the decay rates were known accurately. The invention of the MASS SPECTROMETER after World War I (post-1918) led to the discovery of more than 200 isotopes. Many radioactive elemtns can be used as geologic clocks. Each radioactive element decays at its own nearly constant rate. Once this rate is known, geologists can estimate the length of time over which decay has been occurring by measuring the amount of radioactive parent element and the amount of stable daughter elements Examples: Radioactive parent isotopes and their stable daughter products Radioactive Parent Stable Daughter Potassium 40 Argon 40 Rubidium 87 Strontium 87 Thorium 232 Lead 208 Uranium 235 Lead 207 Uranium 238 Lead 206 Carbon 14 Nitrogen 14 In the above table, note that the number is the

3. Geologic Time: Radiometric Time Scale Discusses the uses of limitations of different radiometric dating techniques. http://pubs.usgs.gov/gip/geotime/radiometric.html

RADIOMETRIC TIME SCALE The discovery of the natural radioactive decay of uranium in 1896 by Henry Becquerel, the French physicist, opened new vistas in science. In 1905, the British physicist Lord Rutherfordafter defining the structure of the atom made the first clear suggestion for using radioactivity as a tool for measuring geologic time directly; shortly thereafter, in 1907, Professor B. B. Boltwood, radiochemist of Yale Uniyersity, published a list of geologic ages based on radioactivity. Although Boltwood's ages have since been revised, they did show correctly that the duration of geologic time would be measured in terms of hundreds-to-thousands of millions of years. A technician of the U.S. Geological Survey uses a mass spectrometer to determine the proportions of neodymium isotopes contained in a sample of igneous rock. The next 40 years was a period of expanding research on the nature and behavior of atoms, leading to the development of nuclear fission and fusion as energy sources. A byproduct of this atomic research has been the development and continuing refinement of the various methods and techniques used to measure the age of Earth materials. Precise dating has been accomplished since 1950. A chemical element consists of atoms with a specific number of protons in their nuclei but different atomic weights owing to variations in the number of neutrons. Atoms of the same element with differing atomic weights are called isotopes. Radioactive decay is a spontaneous process in which an isotope (the parent) loses particles from its nucleus to form an isotope of a new element (the daughter). The rate of decay is conveniently expressed in terms of an isotope's half-life, or the time it takes for one-half of a particular radioactive isotope in a sample to decay. Most radioactive isotopes have rapid rates of decay (that is, short half-lives) and lose their radioactivity within a few days or years. Some isotopes, however, decay slowly, and several of these are used as geologic clocks. The parent isotopes and corresponding daughter products most commonly used to determine the ages of ancient rocks are listed below:

4. A Radiometric Dating Resource List A radiometric dating Resource List. updated links checked, 29 April 2003. The real Toast? Reliability of radiometric dating. Are http://www.tim-thompson.com/radiometric.html

A Radiometric Dating Resource List The real heart of the age-of-the-earth debate (if "debate" is the right word) is always radiometric dating. There are lots of ways to guesstimate ages, and geologists knew the earth was old a long time ago (and I might add that they were mostly Christian creationist geologists). But they didn't know how old . Radiometric dating actually allows the measurement of absolute ages, and so it is deadly to the argument that the earth cannot be more than 10,000 years old. Radiometric methods measure the time elapsed since the particular radiometric clock was reset. Radiocarbon dating, which is probably best known in the general public, works only on things that were once alive and are now dead. It measures the time elapsed since death, but is limited in scale to no more than about 50,000 years ago. Other methods, such as Uranium/Lead, Potassium/Argon, Argon/Argon and others, are able to measure much longer time periods, and are not restricted to things that were once alive. Generally applied to igneous rocks (those of volcanic origin), they measure the time since the molten rock solidified. If that happens to be longer than 10,000 years, then the idea of a young-Earth is called into question. If that happens to be billions of years, then the young-Earth is in big trouble. Priscoan (4.00-4.03 Ga) orthogneisses from northwestern Canada

5. Radiometric Dating And The Geological Time Scale This document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale. Other Links A radiometric dating Resource List. Tim http://www.talkorigins.org/faqs/dating.html

Radiometric Dating and the Geological Time Scale Circular Reasoning or Reliable Tools? Andrew MacRae [Last Update: October 2, 1998] Other Links: A Radiometric Dating Resource List Tim Thompson has collected a large set of links to web pages that discuss radiometric dating techniques and the age of the earth controversy. Overview Introduction Background Biostratigraphy Radiometric dating: Calibrating the time scale ... Acknowledgements Introduction his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale. It is not about the theory behind radiometric dating methods, it is about their application , and it therefore assumes the reader has some familiarity with the technique already (refer to "Other Sources" for more information). As an example of how they are used, radiometric dates from geologically simple, fossiliferous Cretaceous rocks in western North America are compared to the geological time scale. To get to that point, there is also a historical discussion and description of non-radiometric dating methods. The example used here contrasts sharply with the way conventional scientific dating methods are characterized by some critics (for example, refer to discussion in "

6. Radiometric Dating Methods Q&A Plate Tectonics. Probabilities. Racism. radiometric dating. Religion (humanism, etc deals not only with 14C dating but also with other forms of radiometric dating) Dating in Conflict http://www.answersingenesis.org/home/area/faq/dating.asp

UPHOLDING THE AUTHORITY OF THE BIBLE FROM THE VERY FIRST VERSE SEARCH Contact Us Home Store Events ... Support Recommended Resources Answers Book (Semi-technical) Fingerprints of Creation (video) God at Ground Zero In the Minds of Men Does Carbon Dating Disprove the Bible? (booklet) ... Mythology of Modern Dating Methods (Technical) Radioisotopes and the Age of the Earth (Technical) The Young Earth Radiocarbon, Creation, and the Flood (video) Email to a friend Printer-friendly version Radiometric Dating Questions and Answers Alien/UFOs Apologetics Archaeology Arguments NOT to use Bible Biographies - Creationists Cloning Countering the Critics Creation Compromises Creation: Why It Matters Darwin, Charles Design Features Dinosaurs Education Embryonic Recapitulation Environmentalism Flood Fossils Geocentrism Genesis Genetics Geology God History Human Life: Abortion Ice Age Information Theory Jesus Christ Linguistics Mammoths Morality and Ethics Mutations Natural Selection Origin of Life Philosophy Plate Tectonics Probabilities Racism Radiometric Dating Religion (humanism, etc.)

7. The Radiometric Dating Game The radiometric dating Game. Therefore, my main concern is with rocks of the Cambrian periods and later. How radiometric dating works in general. Back to top http://www.cs.unc.edu/~plaisted/ce/dating.html

The Radiometric Dating Game How radiometric dating works in general Why methods in general are inaccurate Why K-Ar dating is inaccurate The branching ratio problem ... Reliability of creationist sources (Some updates to this article are now available. The sections on the branching ratio and dating meteorites need updating.) However, this causes a problem for those who believe based on the Bible that life has only existed on the earth for a few thousand years, since fossils are found in rocks that are dated to be over 500 million years old by radiometric methods, and some fossils are found in rocks that are dated to be billions of years old. If these dates are correct, this calls the Biblical account of a recent creation of life into question. After study and discussion of this question, I now believe that the claimed accuracy of radiometric dating methods is a result of a great misunderstanding of the data, and that the various methods hardly ever agree with each other, and often do not agree with the assumed ages of the rocks in which they are found. I believe that there is a great need for this information to be made known, so I am making this article available in the hopes that it will enlighten others who are considering these questions. Even the creationist accounts that I have read do not adequately treat these issues. At the start, let me clarify that my main concern is not the age of the earth, the moon, or the solar system, but rather the age of life, that is, how long has life existed on earth. Many dating methods seem to give about the same ages on meteorites. Thus radiometric dating methods appear to give evidence that the earth and meteorites are old, if one accepts the fact that decay rates have been constant. However, there may be other explanations for this apparent age. Perhaps the earth was made from older pre-existing matter, or perhaps decay rates were briefly faster for some reason. When one considers the power of God, one sees that any such conclusions are to some extent tentative. For some evidence for a young universe, see

8. Institut Für Geologische Wissenschaften / Geochronologie Uses radiometric dating and classical geochronological methods to constrain the timing of geological processes, primarily in the Eastern Alps, the Carpathian Pannonian region and adjoining area, and the Bohemian Massif. Includes descriptions of several isotopic techniques. http://www.univie.ac.at/geochron/

http://www.univie.ac.at/geologie http://www.univie.ac.at/geologie

9. Leibniz-Labor This laboratory at the University of Kiel provides radiometric dating and studies the use of stable and radioactive isotopes for archaeometry, palaeoclimate research and as tracers in environmental studies. http://www.uni-kiel.de/leibniz/indexe.htm

Leibniz-Labor for Radiometric Dating and Isotope Research Diese Seite gibt es auch in deutscher Sprache The Lab How to find us Description of the lab Telephone and e-Mail list Recent pricelist, datasheets, etc. Job Announcement News What are we doing? The radiocarbon method C-14-AMS dating Conventional C-14 dating Stable isotope measurements Gamma-ray spectroscopy Recent publications Services we offer Institutes at the CAU Institute of Geology and Palaeontology Institute for Ocean Sciences Special Research Project 313 Archeological Institute (German language only) Geomar Other C links Centre for Isotope Research (RUG) National Ocean Sciences AMS Oxford Radiocarbon Accelerator Unit Quaternary Isotope Lab UW ... Radiocarbon Webinfo For questions, comments and corrections of embarrassing errors, please contact: pgrootes@leibniz.uni-kiel.de Last update: November 6th, 2003 (MH)

10. Comments On "The Radiometric Dating Game - Part 2" Comments on David Plaisted s The radiometric dating Game Part 2. KRH = comment by Kevin R. Henke, geologist and advocate of radiometric dating. http://www.tim-thompson.com/plaisted-review2.html

Comments on David Plaisted's "The Radiometric Dating Game" - Part 2 Further Reply to David A. Plaisted's Comments on Radiometric Dating Kevin R. Henke, Ph.D. December 28, 1998 The following text was posted to the talk.origins newsgroup on December 28, 1998. It consists of David Plaisted's response to Kevin Henke's original critique Dr. Henke is currently a post doctoral fellow in the Department of Chemistry at the University of Kentucky Dr. David Plaisted earned his PhD in computer science from Stanford University in 1976, and is currently Professor of Computer Science at the University of North Carolina, Chapel Hill Text was provided by Dr. Kevin Henke, HTML formatting by Tim Thompson. For the readers of Talk.origins and others: In early December, 1998, I commented on David A. Plaisted's anti-radiometric dating article " The Radiometric Dating Game ". David kindly replied to my critique on December 15, 1998. Below I reply further to David's comments of December 15, 1998. My original critique, from early December 1998, is in Part 1 DAP = comment by David A. Plaisted, creationist.

11. - Radiometric Dating Game - Evolutionists claim radiometric dating supports their claims of a multimillion-year history of macro-evolution. They're lying. Last Modified 10 March 2002 How radiometric dating works in general Anomalies of radiometric dating. Why a low anomaly percentage is meaningless http://www.trueorigin.org/dating.asp

Home Feedback Links Books The Radiometric Dating Game David Plaisted How radiometric dating works in general Why methods in general are inaccurate Why K-Ar dating is inaccurate ... Reliability of creationist sources Dr. Plaisted responds to comments and criticisms of this article here However, this causes a problem for those who believe based on the Bible that life has only existed on the earth for a few thousand years, since fossils are found in rocks that are dated to be over 500 million years old by radiometric methods, and some fossils are found in rocks that are dated to be billions of years old. If these dates are correct, this calls the Biblical account of a recent creation of life into question. After study and discussion of this question, I now believe that the claimed accuracy of radiometric dating methods is a result of a great misunderstanding of the data, and that the various methods hardly ever agree with each other, and often do not agree with the assumed ages of the rocks in which they are found. I believe that there is a great need for this information to be made known, so I am making this article available in the hopes that it will enlighten others who are considering these questions. Even the creationist accounts that I have read do not adequately treat these issues. At the start, let me clarify that my main concern is not the age of the earth, the moon, or the solar system, but rather the age of life, that is, how long has life existed on earth. Many dating methods seem to give about the same ages on meteorites. Thus radiometric dating methods appear to give evidence that the earth and meteorites are old, if one accepts the fact that decay rates have been constant. However, there may be other explanations for this apparent age. Perhaps the earth was made from older pre-existing matter, or perhaps decay rates were briefly faster for some reason. When one considers the power of God, one sees that any such conclusions are to some extent tentative. For some evidence for a young universe, see

12. Isochron Dating Generic radiometric dating. The In short, radiometric dating methods give reliable results most of the time, but not always. With http://www.talkorigins.org/faqs/isochron-dating.html

Isochron Dating by Chris Stassen [Last update, September 17, 1998] Overview Generic radiometric dating Potential problems for generic dating Isochron methodology Why isochron data are colinear ... References Generic Radiometric Dating The simplest form of isotopic age computation involves substituting three measurements into an equation of four variables, and solving for the fourth. The equation is the one which describes radioactive decay: The variables in the equation are: P now - The quantity of the parent isotope that remains now. This is measured directly. P orig - The quantity of the parent isotope that was originally present. This is computed from the current quantity of parent isotope plus the accumulated quantity of daughter isotope. halflife - The half-life of the parent isotope. Standard values are used, based on direct measurements. (Constancy of decay rate is covered in the Age of the Earth FAQ age - The value computed from the equation and the other three quantities, is the amount of time which has passed. Solving the equation for "age," and incorporating the computation of the original quantity of parent isotope, we get:

13. TWD -- Radiometric Dating radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth old are fond of attacking radiometric dating methods as being full of http://www.erinet.com/jwoolf/rad_dat.html

An Essay on Radiometric Dating By Jonathon Woolf Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth. All these methods point to Earth being very, very old several billions of years old. Young-Earth creationists that is, creationists who believe that Earth is no more than 10,000 years old are fond of attacking radiometric dating methods as being full of inaccuracies and riddled with sources of error. When I first became interested in the creation-evolution debate, in late 1994, I looked around for sources that clearly and simply explained what radiometric dating is and why young-Earth creationists are driven to discredit it. I found several good sources, but none that seemed both complete enough to stand alone and simple enough for a nongeologist to understand them. Thus this essay, which is my attempt at producing such a source. Contents: I. Theory of Radiometric Dating II. Common Methods of Radiometric Dating III. Possible Sources of Error IV. Creationist Objections to Radiometric Dating ... VI. Summary and Sources I. Theory of radiometric dating What is radiometric dating? Simply stated, radiometric dating is a way of determining the age of a sample of material using the decay rates of radio-active nuclides to provide a 'clock.' It relies on three basic rules, plus a couple of critical assumptions. The rules are the same in all cases; the assumptions are different for each method. To explain those rules, I'll need to talk about some basic atomic physics.

14. More Bad News For Radiometric Dating More Bad News for radiometric dating. Thus, there apparently ARE some problems in that kind of radiometric dating. General unreliability of radiometric dating. http://www.cs.unc.edu/~plaisted/ce/dating2.html

More Bad News for Radiometric Dating Most scientists today believe that life has existed on the earth for billions of years. This belief in long ages for the earth and the existence of life is derived largely from radiometric dating. These long time periods are computed by measuring the ratio of daughter to parent substance in a rock and inferring an age based on this ratio. This age is computed under the assumption that the parent substance (say, uranium) gradually decays to the daughter substance (say, lead), so the higher the ratio of lead to uranium, the older the rock must be. Of course, there are many problems with such dating methods, such as parent or daughter substances entering or leaving the rock, as well as daughter product being present at the beginning. Here I want to concentrate on another source of error, namely, processes that take place within magma chambers. To me it has been a real eye opener to see all the processes that are taking place and their potential influence on radiometric dating. Radiometric dating is largely done on rock that has formed from solidified lava. Lava (properly called magma before it erupts) fills large underground chambers called magma chambers. Most people are not aware of the many processes that take place in lava before it erupts and as it solidifies, processes that can have a tremendous influence on daughter to parent ratios. Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or cause the parent to be enriched relative to the daughter, which would make the rock look younger. This calls the whole radiometric dating scheme into serious question.

15. - Radiometric Dating Game - Evolutionists claim radiometric dating supports their claims of a multimillion-year history of macro-evolution. They re lying. The radiometric dating Game. http://www.trueorigin.org/dating.htm

Home Feedback Links Books The Radiometric Dating Game David Plaisted How radiometric dating works in general Why methods in general are inaccurate Why K-Ar dating is inaccurate ... Reliability of creationist sources Dr. Plaisted responds to comments and criticisms of this article here However, this causes a problem for those who believe based on the Bible that life has only existed on the earth for a few thousand years, since fossils are found in rocks that are dated to be over 500 million years old by radiometric methods, and some fossils are found in rocks that are dated to be billions of years old. If these dates are correct, this calls the Biblical account of a recent creation of life into question. After study and discussion of this question, I now believe that the claimed accuracy of radiometric dating methods is a result of a great misunderstanding of the data, and that the various methods hardly ever agree with each other, and often do not agree with the assumed ages of the rocks in which they are found. I believe that there is a great need for this information to be made known, so I am making this article available in the hopes that it will enlighten others who are considering these questions. Even the creationist accounts that I have read do not adequately treat these issues. At the start, let me clarify that my main concern is not the age of the earth, the moon, or the solar system, but rather the age of life, that is, how long has life existed on earth. Many dating methods seem to give about the same ages on meteorites. Thus radiometric dating methods appear to give evidence that the earth and meteorites are old, if one accepts the fact that decay rates have been constant. However, there may be other explanations for this apparent age. Perhaps the earth was made from older pre-existing matter, or perhaps decay rates were briefly faster for some reason. When one considers the power of God, one sees that any such conclusions are to some extent tentative. For some evidence for a young universe, see

16. The Way It Really Is: Little-known Facts About Radiometric Dating The way it really is littleknown facts about radiometric dating. Many people think that radiometric dating has proved the Earth is millions of years old. http://www.answersingenesis.org/creation/v24/i4/radiometric.asp

UPHOLDING THE AUTHORITY OF THE BIBLE FROM THE VERY FIRST VERSE SEARCH Contact Us Home Store Events ... Volume 24 Issue 4 First published: Creation September 2002 Browse this issue Subscribe to Creation Magazine The way it really is: little-known facts about radiometric dating by Tas Walker Long-age geologists will not accept a radiometric date unless it matches their pre-existing expectations. However, although we can measure many things about a rock, we cannot directly measure its age. For example, we can measure its mass, its volume, its colour, the minerals in it, their size and the way they are arranged. We can crush the rock and measure its chemical composition and the radioactive elements it contains. But we do not have an instrument that directly measures age. Before we can calculate the age of a rock from its measured chemical composition, we must assume what radioactive elements were in the rock when it formed. And then, depending on the assumptions we make, we can obtain any date we like. Field relationships A geologist works out the relative age of a rock by carefully studying where the rock is found in the field. The field relationships, as they are called, are of primary importance and all radiometric dates are evaluated against them.

17. TWD -- Radiometric Dating An Essay on radiometric dating. By Jonathon Woolf. radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth. http://my.erinet.com/~jwoolf/rad_dat.html

An Essay on Radiometric Dating By Jonathon Woolf Radiometric dating methods are the strongest direct evidence that geologists have for the age of the Earth. All these methods point to Earth being very, very old several billions of years old. Young-Earth creationists that is, creationists who believe that Earth is no more than 10,000 years old are fond of attacking radiometric dating methods as being full of inaccuracies and riddled with sources of error. When I first became interested in the creation-evolution debate, in late 1994, I looked around for sources that clearly and simply explained what radiometric dating is and why young-Earth creationists are driven to discredit it. I found several good sources, but none that seemed both complete enough to stand alone and simple enough for a nongeologist to understand them. Thus this essay, which is my attempt at producing such a source. Contents: I. Theory of Radiometric Dating II. Common Methods of Radiometric Dating III. Possible Sources of Error IV. Creationist Objections to Radiometric Dating ... VI. Summary and Sources I. Theory of radiometric dating What is radiometric dating? Simply stated, radiometric dating is a way of determining the age of a sample of material using the decay rates of radio-active nuclides to provide a 'clock.' It relies on three basic rules, plus a couple of critical assumptions. The rules are the same in all cases; the assumptions are different for each method. To explain those rules, I'll need to talk about some basic atomic physics.

18. Age Of The Earth radiometric dating from The Evolution Evidence Page. Scientists have Creation Science Arguments Against radiometric dating. Now, what http://www.gate.net/~rwms/AgeEarth.html

Radiometric Dating from The Evolution Evidence Page Scientists have settled on the age of the earth of about 4.6 billion years as a result of research started almost 50 years ago. This conclusion was based upon carefully designed and conducted experiments that compared the ratios in rock samples of parent elements to daughter elements ( some of which would have been from radioactive decay of the parent, some of which may have been present in the sample at the time of formation). Since radioactive decay is known to occur at a constant rate, the age of a rock can be determined from the ratio of the parent element to the daughter element. The concerns about these dating methods were exactly the same that creationists continue to raise - presence of the daughter element at the time the rock was formed and possible loss / gain of either the parent or daughter element at some point in the history of the rock. For this reason, the tests were designed to account for those possibilities. The other problem to avoid when dating rocks is the possibility that changes to the rock have caused loss or gain of either the parent or daughter element - this would lead to a false date (too old if parent element were lost, too young if daughter element were lost). I know of two methods that have been designed that can account for this possibility - isochron dating and the uranium-thorium-lead discordia / concordia method (actually three independent age calculations for one sample). Both of these methods have internal checks for the possible loss / gain of elements to the rock.

19. Radiometric Dating - Wikipedia, The Free Encyclopedia radiometric dating. The most common form of radiometric dating is radiocarbon dating, which is based on the decay of carbon14 to carbon-12. http://en.wikipedia.org/wiki/Radiometric_dating

20. Radiometric Dating Stephen A. Nelson. radiometric dating. It provided a means by which the age of the Earth could be determined independently. Principles of radiometric dating. http://www.tulane.edu/~sanelson/geol212/radiometric_dating.htm

Geology 212 Petrology Prof. Stephen A. Nelson Radiometric Dating Prior to 1905 the best and most accepted age of the Earth was that proposed by Lord Kelvin based on the amount of time necessary for the Earth to cool to its present temperature from a completely liquid state. Although we now recognize lots of problems with that calculation, the age of 25 my was accepted by most physicists, but considered too short by most geologists. Then, in 1896, radioactivity was discovered. Recognition that radioactive decay of atoms occurs in the Earth was important in two respects: It provided another source of heat, not considered by Kelvin, which would mean that the cooling time would have to be much longer. It provided a means by which the age of the Earth could be determined independently. Principles of Radiometric Dating Radioactive decay is described in terms of the probability that a constituent particle of the nucleus of an atom will escape through the potential (Energy) barrier which bonds them to the nucleus. The energies involved are so large, and the nucleus is so small that physical conditions in the Earth (i.e. T and P) cannot affect the rate of decay. The rate of decay or rate of change of the number N of particles is proportional to the number present at any time, i.e.

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