41. Evolution Happens Radiometric Dating Page APPENDIX Common Misconceptions Regarding radiometric dating Methods From “radiometric dating A Christian Perspective”, 2nd Edition, by Dr. Roger C. Wiens. http://www.evolutionhappens.net/radiometric.htm

APPENDIX: Common Misconceptions Regarding Radiometric Dating Methods From Radiometric Dating: A Christian Perspective , 2nd Edition, by Dr. Roger C. Wiens There are a number of misconceptions that seem especially prevalent among Christians. Most of these topics are covered in the paper at the link listed above, but they are reviewed briefly here for clarity. References below are to sections of the paper available on the web. Radiometric dating is based on index fossils whose dates were assigned long before radioactivity was discovered. This is not at all true, though it is implied by some young-Earth literature. Radiometric dating is based on the half-lives of the radioactive isotopes. These half-lives have been measured over the last 40-90 years. They are not calibrated by fossils. No one has measured the decay rates directly; we only know them from inference. Decay rates have been directly measured over the last 40-100 years. In some cases a batch of the pure parent material is weighed and then set aside for a long time and then the resulting daughter material is weighed. In many cases it is easier to detect radioactive decays by the energy burst that each decay gives off. For this a batch of the pure parent material is carefully weighed and then put in front of a Geiger counter or gamma-ray detector. These instruments count the number of decays over a long time. If the half-lives are billions of years, it is impossible to determine them from measuring over just a few years or decades.

42. Radiometric Dating, Or Isotopic Dating, Or Radioactive Dating (chronology) -- B Cenozoic Era, geological time scale, hydrology, mass spectrometry, plate tectonics, research, tektites, lunar rocks, meteorites, origin of chemical elements http://www.britannica.com/eb/topic-489205/radiometric-dating

Already a member? LOGIN Encyclopædia Britannica - the Online Encyclopedia Home Blog Advocacy Board ... Free Trial Britannica Online Content Related to this Topic Shopping New! Britannica Book of the Year The Ultimate Review of 2007. 2007 Britannica Encyclopedia Set (32-Volume Set) Revised, updated, and still unrivaled. New! Britannica 2008 Ultimate DVD/CD-ROM The world's premier software reference source. radiometric dating, or isotopic dating, or radioactive dating (chronology) A selection of articles discussing this topic. lunar rocks One new and fundamental result has come from radiometric age dating of the samples. When a rock cools from the molten to the solid state, its radioactive isotopes are immobilized in mineral crystal lattices and then decay in place. Knowing the rate of decay of one nuclear species (nuclide) into another, scientists can, in principle, use the ratios of decay products as a clock to measure the... meteorites ...or when they were last heated and the strontium isotopes in them rehomogenized. Consequently, other evidence about a rock or suite of rocks is needed to determine what the isochron is actually dating. If the data points for minerals or rocks do not fall on a line, it indicates that the system has been disturbed and cannot be used for dating. Shock is the most common cause of disturbed... origin of chemical elements Radioactive elements in the Earth, the Moon, and in meteorites can provide useful information about the ages of these objects and about the dates of formation of the heavy elements themselves. The elements uranium and thorium gradually decay into lead, different isotopes of lead arising from the various isotopes of uranium and thorium; some isotopes of lead are, however, not produced by any...

43. NCSE Resource radiometric dating of rocks and minerals using naturally occurring, longlived radioactive isotopes is troublesome for young-earth creationists because the http://www.ncseweb.org/resources/rncse_content/vol20/4180_radiometeric_dating_do

National Center for Science Education Defending the Teaching of Evolution in the Public Schools Home On the Road NCSE Store Links ... Search Radiometeric Dating Does Work! by G. Brent Dalrymple Originally published in RNCSE 20 (3): 14-19. The version on the web might differ slightly from the print publication. The creationist approach of focusing on examples where radiometric dating yields incorrect results is a curious one for two reasons. First, it provides no evidence whatsoever to support their claim that the earth is very young. If the earth were only 6000–10 000 years old, then surely there should be some scientific evidence to confirm that hypothesis; yet the creationists have produced not a shred of it so far. Where are the data and age calculations that result in a consistent set of ages for all rocks on earth, as well as those from the moon and the meteorites, no greater than 10 000 years? Glaringly absent, it seems. Second, it is an approach doomed to failure at the outset. Creationists seem to think that a few examples of incorrect radiometric ages invalidate all of the results of radiometric dating, but such a conclusion is illogical. Even things that work well do not work well all of the time and under all circumstances. Try, for example, wearing a watch that is not waterproof while swimming. It will probably fail, but what would a reasonable person conclude from that? That watches do not work? Hardly. A few verified examples of incorrect radiometric ages are simply insufficient to prove that radiometric dating is invalid. All they indicate is that the methods are not infallible. Those of us who have developed and used dating techniques to solve scientific problems are well aware that the systems are not perfect; we ourselves have provided numerous examples of instances in which the techniques fail. We often test them under controlled conditions to learn when and why they fail so we will not use them incorrectly. We have even discredited entire techniques. For example, after extensive testing over many years, it was concluded that uranium-helium dating is highly unreliable because the small helium atom diffuses easily out of minerals over geologic time. As a result, this method is not used except in rare and highly specialized applications. Other dating techniques, like K-Ar (potassium-argon and its more recent variant

44. Radiometric Dating One of the tools at the disposal of researchers is the radiometric dating technique. There are many such techniques, but each relies on the principle http://anthropology.si.edu/humanorigins/whatshot/1998/radio.html

Radiometric Dating, What is It? You've heard us mention radiometric dating. Have you wondered what it is? As in history, where the temporal context of an event is just as important as the event itself, the chronological position of an early human fossil is critical to the understanding of the species. Without proper understanding of the time period represented by an early human species, no evolutionary relationship can be interpreted. Since evolution is change over time, and time is a variable that must be controlled. One of the tools at the disposal of researchers is the radiometric dating technique. There are many such techniques, but each relies on the principle borrowed from physics that radioactive elements will decay at a constant rate. So an object can be dated using the clock created by the continual "click" of the radioactive atoms. Another technique of particular use to paleoanthropologists is the K/ AR (Potassium-40/Argon-40) technique. This technique is specific to volcanic materials, dating the breakdown of the radioactive Potassium-40 isotope into the stable and inert gas Argon-40.

45. Radiometric Dating Radiometric measurements of time discusses how geological time can be measured accurately by looking at the decay rate of radioactive components. http://sci.waikato.ac.nz/evolution/RadiometricDating.shtml

The Evolution of Life Fossils Geological Time Geological Time Geologic Time Scale Plate Tectonics Radiometric Dating Deep Time ... Geological History of New Zealand Radiometric Dating Radiometric measurements of time Since the early twentieth century scientists have found ways to accurately measure geological time. The discovery of radioactivity in uranium by the French physicist, Henri Becquerel , in 1896 paved the way of measuring absolute time. Shortly after Becquerel's find, Marie Curie , a French chemist, isolated another highly radioactive element, radium . The realisation that radioactive materials emit rays indicated a constant change of those materials from one element to another. The New Zealand physicist Ernest Rutherford , suggested in 1905 that the exact age of a rock could be measured by means of radioactivity. For the first time he was able to exactly measure the age of a uranium mineral. When Rutherford announced his findings it soon became clear that Earth is millions of years old.

46. Radiometeric Dating Links radiometric dating uses the known decay rates of radioactive elements to The following links provide extensive evidence that radiometric dating methods http://paleo.cc/ce/dating.htm

Radiometric Dating Links Compiled by Glen Kuban. Updated July, 2006 Radiometric dating uses the known decay rates of radioactive elements to calculate the age of rocks. These methods and others have lead most scientists to conclude that the Earth is approximately 4.6 billion years old. Most strict creationists, however, maintain that the earth is less than about 15,000 years old (some say less than 10,000 years old), and that radiometric dating methods are unreliable. The following links provide extensive evidence that radiometric dating methods are generally reliable and accurate, and largely in agreement with each other a number of other, independent dating methods. Radiometric Resource List by Tim Thompson Radiometric Dating: a Christian Perspective, by Roger Wiens of ASA Radiocarbon Web Info Minimum-age indicators by "Razd" Radio Dating and the Creation Scientists Consistent Radiometric Dates Radiometric Dating, Paleosols and the Geologic Column: Three strikes against Young Earth Creationism ... Radioisotopes and the Age of The Earth , by J.G. Meert A review of ICR's "R.A.T.E." project criticizing radiometric dating

47. Mick's Blog » Radiometric Dating:A Christian Perspective radiometric datingthe process of determining the age of rocks from the decay of their radioactive elementshas been in widespread use for over half a http://blog.planetpreterist.com/index.php?itemid=461

48. HDER Chapter 12 Answer The radiometric dating methods rely upon radioactive elements contained in Do the radiometric dating methods possess the three qualifications to http://www.parentcompany.com/handy_dandy/hder12.htm

<% function hideFromBots(strE) dim bots, re, c bots = Array("^EmailSiphon","^EmailWolf","^ExtractorPro","^Mozilla.*NEWT","^Crescent","^CherryPicker","^[Ww]eb[Bb]andit","^WebEMailExtrac.*","^NICErsPRO","^Telesoft","^Zeus.*Webster","^Microsoft.URL","^Mozilla/3.Mozilla/2.01","^Xenu.*Link.*Sleuth.*","^EmailCollector") for each spambot in bots Set re = new RegExp re.IgnoreCase = false re.global = false re.Pattern = spambot if re.Test(request.servervariables("HTTP_USER_AGENT")) then c=c+1 next if c>0 then hideFromBots="Email address witheld" else hideFromBots=strE end if end function %> Home Online Books Handy Dandy Evolution Refuter Handy Dandy Evolution Refuter Chapter 12 - How Old is the Earth? Haven't scientists proved that the earth is billions of years old? Answer: As was shown in the first chapter where science was defined, the study of origins and earth prehistory is, strictly speaking, beyond the powers of the scientific method. No humans were present to observe the events, and the events which occurred are unknown and cannot be repeated experimentally. All of the evidence from the rocks is circumstantial and can be interpreted in various ways. Thus it is not possible to "prove" that the earth is billions of years old. A number of surveys of the subject from the biblical creation perspective have been published. They are essentially critiques of the methods used by the secular establishment to estimate the ages of minerals, rocks and other geological materials.

49. Radiometric Dating@Everything2.com The principles explained above are central to the various specific practices of radiometric dating. Below are four basic types of this technique. http://everything2.com/index.pl?node_id=1214594

50. Geology: Radiometric Dating Kimberly, radiometric dating is just one line of evidence of the great age of Earth and the Universe. You correctly see that the crux of this method relies http://en.allexperts.com/q/Geology-1359/radiometric-dating-1.htm

zJs=10 zJs=11 zJs=12 zJs=13 zc(5,'jsc',zJs,9999999,'') AllExperts Experts Search Geology Volunteer Answers to thousands of questions Home More Questions Question Library ... Free Encyclopedia zmhp('style="color:#fff"') More Geology Answers Question Library Ask a question about Geology Volunteer ... Link to Us About Dr Thomas Bell Expertise I can answer questions regarding surface earth processes and the chemical transformations that sediments and rocks undergo with burial. I can also answer questions regarding deep time, the evolution of the elements, and the last 4.5 billion years of earth history. I specialize in metallic ore forming processes, the major geologic time periods when they were produced and what they tell us about the evolution of our planet. Learn more about my professional interests at Stratamodel.com Experience I am a professional consulting geologist with a background in the petroleum, mining, environmental, and geotechnical industries with over 25 years of experience. Education/Credentials Ph.D., Geology, University of California at Berkeley, 1984 M.A., Geology, University of California at Berkeley, 1980 B.S., Geology, San Jose State University, 1978 You are here: Experts Science Geology Geology Topic: Geology Expert: Dr Thomas Bell Date: Subject: radiometric dating Question Hi: I was wondering if you could explain in laymen's terms HOW we know the half life of a radioactive element. I have been reading websites on the subject and they either don't answer this question at all just assume the half life or they explain it in complex terms. Are we SURE of these numbers?

51. Radiometric Dating Flaws The validity of radiometric dating depends upon the three listed assumptions being correct. The decay rate being a constant is probably true but the other http://emporium.turnpike.net/C/cs/basics/sld024.htm

Notes: Creationists have also advanced theories which may explain why rock samples appear to have old ages, and question the validity of the "isochron" dating procedure, which uses multiple samples. The bottom line is that radiometric dating procedures don't provide the consistent absolute dating method we would like to have. Go to Creation Science home page

52. Radiometric Dating Definition of radiometric dating. See a map of radiometric dating in the Visual Thesaurus Cite Print Email; Bookmark http://www.infoplease.com/ipd/A0614793.html

Site Map FAQ in All Infoplease Almanacs Biographies Dictionary Encyclopedia Spelling Checker Daily Almanac for Jan 24, 2008 Search White Pages Skip Navigation Home Almanacs ... Word of the Day Editor's Favorites 2007 Year in Review Black History Month Leap Year Martin Luther King Day ... 2008 Calendar Search: Infoplease Info search tips Search: Biographies Bio search tips Dictionary Find definitions for: any method of determining the age of earth materials or objects of organic origin based on measurement of either short-lived radioactive elements or the amount of a long-lived radioactive element plus its decay product. Also called radioactive dating. Random House Unabridged Dictionary, radiometer radiomicrometer See a map of "radiometric dating" in the Visual Thesaurus Cite Print Email ... Add to Reddit Related Content Daily Word Quiz: synecdoche Analogy of the Day: Spelling Bee: dissonant Crossword: Crossword Puzzle Guide Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Find definitions for: Infoplease Tools Calculator Spelling Checker Place Finder Distance Calculator ... Year by Year Career Center Job Search Post Your Resume Continuing Ed.

53. Radiometric Dating - Hutchinson Encyclopedia Article About Radiometric Dating Hutchinson encyclopedia article about radiometric dating. radiometric dating. Information about radiometric dating in the Hutchinson encyclopedia. http://encyclopedia.farlex.com/Radiometric dating

Domain='thefreedictionary.com' word='radiometric dating' Printer Friendly 759,470,398 visitors served. TheFreeDictionary Google Word / Article Starts with Ends with Text subscription: Dictionary/ thesaurus Medical dictionary Legal dictionary Financial dictionary Acronyms Idioms Encyclopedia Wikipedia encyclopedia Hutchinson encyclopedia radiometric dating Also found in: Dictionary/thesaurus Encyclopedia Wikipedia 0.09 sec. write_ads(AdsNum, 0) radiometric dating Method of dating rock by assessing the amount of radioactive decay of naturally occurring isotopes radiocarbon dating , employing the half-life of the isotope carbon-14, which is naturally present in organic tissue. Radiometric methods have been applied to the decay of long-lived isotopes, such as potassium-40, rubidium-87, thorium-232, and uranium-238, which are found in rocks. These isotopes decay very slowly and this has enabled rocks as old as 3,800 million years to be dated accurately. Carbon dating can be used for material between 1,000 and 100,000 years old. Potassium dating is used for material more than 100,000 years old

54. Siberian Traps - Radiometric Dating Published radiometric ages, coded according to technique and sample type, for the Siberian Traps and contiguous regions. Modified after Figure 2 in Reichow http://www.le.ac.uk/gl/ads/SiberianTraps/Dating.html

The Siberian Traps - Radiometric Dating Home Introduction History of Research Geological Setting Area and Volume Radiometric Dating Lithostratigraphy Geochemistry Origin of Magmas Plume or not? ... Andy's Homepage Published Ar/ Ar determinations (whole-rock and plagioclase separates) exist for basalts from Noril'sk, Putorana, Maymecha-Kotuy, and the West Siberian Basin. Normalised to a common standard, they all lie within error of each other, and indicate a magmatic crystallization age of between 248-250 Ma (figure, right). Ar/ Ar measurements of biotite from intrusive rocks tend to give slightly older ages, possibly related to the presence of excess argon. Ar/ Ar deteminations of sanidine feldspars from tuffs above and below the Permo-Triassic boundary at Meishan, China (grey bar, right) suggest an age for the boundary of just less than 250 Ma. This age is (within error) the same as the Ar/ Ar age of the basalts from Siberia. Zircons and baddeleyites from intrusions at Noril'sk, together with perovskite, zircon and baddeleyite from Maymecha-Kotuy, give U/Pb concordia ages that are slightly but significantly older than the Ar/ Ar ages. Whilst there are fewer U/Pb ages, they do tend to be very precise. Similarly, the U/Pb (zircon) age of the Meishan and Shangsi tuffs is slighty older than the equivalent

55. Geologic Radiometric It was not until radiometric dating that paleontologist and geologist could put radiometric dating is based upon a simple chemical property of isotopes. http://www.starsandseas.com/SAS Evolution/SAS geoltime/geotime_radiometric.htm

Geologic Time Scales Eras of the Earth Law of Superposition Radiometric Dating References: Radiometric Dating Chronological Methods 9 - Potassium-Argon Dating The Radiometric Dating Game Radiometric Dating and the Geological Time Scale Chronological Methods 8 - Radiocarbon Dating Uranium Series Decay Scheme Return SAS Home e-mail Kevin C. Hartzog Geologic Time Scales Radiometric Dating It was not until radiometric dating that paleontologist and geologist could put a reliable number on the Eons and Periods of Earth's past. Radiometric dating is based upon a simple chemical property of isotopes. Atoms, such as carbon, may have more than one form. In the case of carbon, it may have 12 or 14 neutrons. Both occur naturally, but carbon-12 is more stable than carbon-14. So overtime, carbon-14 will decay, losing two neutrons, and become carbon-12. The processes that release carbon dioxide will create some carbon dioxide with C-12, while a certain proportion of the carbon dioxide will have C-14. Through photosynthesis, plants incorporate carbon dioxide into sugar, which, through the carbon cycle, will consumed by animals. As long as they live, both plants and animals will maintain a constant ratio of C-12:C-14. But when they die, plants and animals do not consume carbon products. Over time their C-14 will turn into C-12 by losing 2 neutrons, changing the C-12:C-14 ratio. The rate that C-14 turns into C-12 is constant, so by measuring the C-12:C-14 ratio in a fossil, paleontologist can put a fairly accurate date on when that organism died.

56. Carbon Dating: Why You Cant Trust It Or Other Radiometric Dating Methods. Creati reasons why you cant trust carbon dating creationist creationism evolution dinosaurs. http://www.angelfire.com/mi/dinosaurs/carbondating.html

The Bible and Radiometric dating (The Problem with Carbon 14 and other dating methods). Many people are under the false impression that carbon dating proves that dinosaurs and other extinct animals lived millions of years ago. What many do not realize is that carbon dating is not used to date dinosaurs. The reason? Carbon dating is only accurate back a few thousand years. So if scientists believe that a creature lived millions of years ago, then they would need to date it another way. But there is the problem. They assume dinosaurs lived millions of years ago (instead of thousands of years ago like the bible says). They ignore evidence that does not fit their preconceived notion. What would happen if a dinosaur bone were carbon dated? - At Oak Ridge National Laboratory, Scientists dated dinosaur bones using the Carbon dating method. The age they came back with was only a few thousand years old. This date did not fit the preconceived notion that dinosaurs lived millions of years ago. So what did they do? They threw the results out. And kept their theory that dinosaurs lived "millions of years ago" instead. This is common practice.

57. Radiometric Dating Is the Earth really billions of years old? radiometric dating does not prove an Old Earth any more than recorded history proves a young one. http://www.earthage.org/EarthOldorYoung/Radiometric Dating, and The Age of the E

Radiometric Dating and the Age of the Earth Part One of a Five-Part Series on The Age of the Earth. The only dating methods discussed (over and over again) by evolution-believing scientists and the mass media are ones that supposedly "prove" that the earth is billions of years old. One of the most popular of these is known as radiometric dating. However, not as well known is the fact that such methods have a number of serious flaws which are usually glossed over, or ignored when writing on, or discussing this subject in public. With the exception of Carbon-14, radiometric dating is used to date either igneous or metamorphic rocks that contain radioactive elements such as uranium. And even though various radioactive elements have been used to "date" these rocks, for the most part, the methods are basically the same. They consist of measuring the amount of radioactive (mother) element and comparing it to the amount of stable (daughter) element. A discussion of the Uranium/Lead method follows. Uranium is radioactive, which means it is in the process of changing from an unstable element into a stable one. The most common form is uranium-238. It has a half-life of about 4.5 billion years. This means that if you had some pure uranium-238 with no lead in it, 4.5 billion years later one half of it would have decayed into its stable daughter product (lead-206). And after 9 billion years there would be 75% lead and 25% uranium, and so on. Few people realize it but all radiometric dating methods require making at least three assumptions. These are:

58. A Radiometric Dating Resource List The real heart of the ageof-the-earth debate (if debate is the right word) is always radiometric dating. There are lots of ways to guesstimate ages, http://www.evcforum.net/RefLib/RadiometricDatingEvo.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. As of January, 1999, The oldest rocks found on earth are 4.031 ± 0.003 billion years old (meaning it has been that long since the molten rocks solidified and thus reset their internal clocks). This is reported in the paper

59. Dating Fossils II: Radiometric Dating radiometric dating is a more precise type of dating used on fossils. http://www.suite101.com/article.cfm/4003/38275

GA_googleAddSlot("ca-pub-7332027313721357", "com_scienceandnature_top_ATF_468x060"); GA_googleAddAttr("language", "com"); GA_googleAddAttr("section", "scienceand"); GA_googleAddAttr("category", "paleontolo"); hiring freelance writers today's articles sign in Home ... Paleontology Dating Fossils II: Radiometric Dating Dating Fossils II: Radiometric Dating Beverly Eschberger Articles in this Topic Discussions in this Topic May 5, 2000 In my last article, I talked about how paleontologists use relative dating to determine the approximate age of fossils. Relative dating has its drawbacks, most notably that the ages we can get from relative dating are very approximate. To be more precise, paleontologists are able to use a technique calle radiometric dating or radioisotope dating. In radiometric dating, scientists look at the ratios of naturally occuring radioactive isotopes (atoms that carry an electrical charge) found in igneous rocks. These unstable radioactive isotopes decay to non-radioactive elements at constant rates, known as the element's "half-life" . This means that after the time of the half-life, half of the radioactive isotopes would have decayed to the non-radioactive form; so the ratio of radioactive to non-radioactive element would be 50:50. After another half-life, one-half of the remaining radioactive isotopes would have decayed to the non-radioactive element; so the ratio of radioactive to non-radioactive element would now be 25:75. (Half of the 50% remaining radioactive isotope decays, leaving half of it, or 25% of the original element, as radioactive, and the other half, 25% of the original element, as non-radioactive.)

60. How Does Radiometric Dating Fit With The View Of A Young Earth? How does radiometric dating fit with the view of a young earth? Is the earth billions of years old, or thousands of years old? http://www.gotquestions.org/radiometric-dating.html

How does radiometric dating fit with the view of a young earth? Question: "How does radiometric dating fit with the view of a young earth?" Answer: Radiometric dating is a method which scientists use to determine the age of various specimens, mainly inorganic matter (rocks, etc), though there is one radiometric dating technique, radiocarbon dating, which is used to date organic specimens. How do these dating techniques work? Basically, scientists take advantage of a natural process by which unstable radioactive “parent” isotopes decay into stable “daughter” isotopes spontaneously over time. Uranium-238 (U238) for example is an unstable radioactive isotope which decays into Lead-206 (Pb206) naturally over time (it goes through 13 unstable intermediate stages before it finally stabilizes into Pb206). In this case, U238 is the “parent” and Pb206 is the “daughter.” Scientists begin by measuring how long it takes for a parent isotope to decay into a daughter isotope. In this particular case, it takes 4,460,000,000 years for half of a sample of U238 to decay into Pb206. It takes another 4,460,000,000 years for half of the remaining sample to decay into Pb206 and then another 4,460,000,000 years for half of what’s then left to decay and so on. The time it takes for half of a sample to decay is called a “half-life.” By measuring radioactive half-lives, by measuring how much parent and daughter are present in any given specimen, and by making certain key assumptions, scientists believe they are able to accurately determine the age of a specimen. The measurements involved can be quite accurate. The question is what are the underlying key assumptions and how reliable are they?

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