Radiometric dating In , shortly after the discovery of radioactivity , the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase with age. After estimating the rate of this radioactive change, he calculated that the absolute ages of his specimens ranged from million to 2. Though his figures were too high by about 20 percent, their order of magnitude was enough to dispose of the short scale of geologic time proposed by Lord Kelvin. Versions of the modern mass spectrometer were invented in the early s and s, and during World War II the device was improved substantially to help in the development of the atomic bomb. Soon after the war, Harold C. Wasserburg applied the mass spectrometer to the study of geochronology. This device separates the different isotopes of the same element and can measure the variations in these isotopic abundances to within one part in 10, By determining the amount of the parent and daughter isotopes present in a sample and by knowing their rate of radioactive decay each radioisotope has its own decay constant , the isotopic age of the sample can be calculated.
Radiometric Dating: Problems with the Assumptions
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.
Radiometric dating of rocks and minerals using naturally occurring, long-lived radioactive isotopes is troublesome for young-earth creationists because the techniques have provided overwhelming evidence of the antiquity of the earth and life.
The nucleus contains two fewer protons and two fewer neutrons. Beta 1 electron One neutron decays to form a proton and an electron, which is emitted. If an element decays by losing an alpha particle, it will lose 2 protons and 2 neutrons. If an atom decays by losing a beta particle, it loses just one electron. So what does this have to do with the age of Earth? Radioactive decay eventually results in the formation of stable daughter products.
Radioactive materials decay at known rates. As time passes, the proportion of radioactive isotopes will decrease and the proportion of daughter isotopes will increase. A rock with a relatively high proportion of radioactive isotopes is probably very young, while a rock with a high proportion of daughter products is probably very old. Scientists measure the rate of radioactive decay with a unit called half-life. The half-life of a radioactive substance is the amount of time, on average, it takes for half of the atoms to decay.
For example, imagine a radioactive substance with a half-life of one year.
Dear Science: How do we know how old the Earth is?
This is what archaeologists use to determine the age of human-made artifacts. But carbon dating won’t work on dinosaur bones. The half-life of carbon is only 5, years, so carbon dating is only effective on samples that are less than 50, years old. Dinosaur bones, on the other hand, are millions of years old — some fossils are billions of years old. To determine the ages of these specimens, scientists need an isotope with a very long half-life.
Some of the isotopes used for this purpose are uranium , uranium and potassium , each of which has a half-life of more than a million years.
The Uranium Dating Method Page 3 Generation of Palaeocene Adakitic Andesites According to the article 17 this rock formation from North Eastern China was dated in by scientists from China and Japan. According to the essay the true age is: “Palaeocene (c. Ma) adakitic andesites from the.
Relative dating Studies of strata , the layering of rocks and earth, gave naturalists an appreciation that Earth may have been through many changes during its existence. These layers often contained fossilized remains of unknown creatures, leading some to interpret a progression of organisms from layer to layer. Lomonosov’s ideas were mostly speculative. In the Comte du Buffon tried to obtain a value for the age of Earth using an experiment: He created a small globe that resembled Earth in composition and then measured its rate of cooling.
This led him to estimate that Earth was about 75, years old. Other naturalists used these hypotheses to construct a history of Earth , though their timelines were inexact as they did not know how long it took to lay down stratigraphic layers. This was a challenge to the traditional view, which saw the history of Earth as static,[ citation needed ] with changes brought about by intermittent catastrophes. Many naturalists were influenced by Lyell to become “uniformitarians” who believed that changes were constant and uniform.
His calculations did not account for heat produced via radioactive decay a process then unknown to science or, more significantly, convection inside the Earth, which allows more heat to escape from the interior to warm rocks near the surface.
How Do Scientists Determine the Age of Dinosaur Bones?
As Creation magazine has been continuously published since , we are publishing some of the articles from the archives for historical interest, such as this. For teaching and sharing purposes, readers are advised to supplement these historic articles with more up-to-date ones suggested in the Related Articles and Further Reading below. The radiometric evidence for a 4. The basic theory of radiometric dating is briefly reviewed.
What are the Methods Used for Knowing the Age of the Earth? The following are some of the common methods used for the purpose of determining the age of earth: (a) Uranium-lead method. therefore, the age of the rock. This method is especially useful for dating relatively recent materials up to 70, years. CONCLUSION.
Uranium technique raises dinosaur question 02 February Share A new technique for dating fossils based on uranium’s radioactive properties could mean that palaeontologists will have to revise their theories on the end of the dinosaurs. Larry Heaman holds the sauropod specimen analysed using the new technique Image: University of Alberta A Canadian research team has used a new uranium-lead U-Pb dating technique to show that a fossilised dinosaur bone found in New Mexico is only A team led by Larry Heaman of the University of Alberta’s Department of Earth and Atmospheric Sciences used the method to determine the age of the fossilised femur of a sauropod, a herbivorous dinosaur.
The in situ U-Pb technique involves laser ablation to remove minute particles of the fossil which then undergo isotopic analysis. The results have now been published in Geology, the journal of the Geological Society of America. Uranium has a half-life of over million years, while uranium has a half-life of about 4. These properties mean that the radioactive decay of uranium to lead has previously been used to measure the age of rocks, including those of some of the oldest on Earth, but its use in direct dating of fossils is new.
Living bone contains very low levels of uranium. During fossilisation — typically within years after death — bone becomes enriched in elements including uranium, which decays spontaneously to lead over time. Therefore by measuring the ratio of uranium to lead in a sample its absolute age can be determined.
The Radiometric Dating Game
This age is obtained from radiometric dating and is assumed by evolutionists to provide a sufficiently long time-frame for Darwinian evolution. And OE Christians theistic evolutionists see no problem with this dating whilst still accepting biblical creation, see Radiometric Dating – A Christian Perspective. This is the crucial point: Some claim Genesis in particular, and the Bible in general looks mythical from this standpoint. A full discussion of the topic must therefore include the current scientific challenge to the OE concept.
• radiometric dating (which uses the concept of radioactive decay) is the most common method of absolute dating Uranium – Lead Dating Method • Uranium is a radioactive isotope that decays in a series of the age of the Earth has been estimated to be approximately billion years • The oldest rock sample on record is a.
Fission track analysis Radiocarbon Dating Carbon is a very special element. In combination with hydrogen it forms a component of all organic compounds and is therefore fundamental to life. Libby of the University of Chicago predicted the existence of carbon before it was actually detected and formulated a hypothesis that radiocarbon might exist in living matter. Willard Libby and his colleague Ernest Anderson showed that methane collected from sewage works had measurable radiocarbon activity whereas methane produced from petroleum did not.
Perseverance over three years of secret research to develop the radiocarbon method came into fruition and in Libby received the Nobel Prize for chemistry for turning his vision into an invaluable tool. The basic principle Carbon has three naturally occurring isotopes , with atoms of the same atomic number but different atomic weights.
Uranium Uranium is a fissile isotope of uranium that is bred from thorium as part of the thorium fuel cycle. Uranium was investigated for use in nuclear weapons and as a reactor fuel; however, it was never deployed in nuclear weapons or used commercially as a nuclear fuel. It has a half-life of , years.
Table 1. The Uranium/Lead dates 11 are up to sixteen billion years older than the Rubidium/Strontium and Neodymium/Samarium dates. The Thorium/Lead dates are up to thirty six billion years older. The so called true age is just a guess.
Radiometric Dating Does Work! Radiometric dating of rocks and minerals using naturally occurring, long-lived radioactive isotopes is troublesome for young-earth creationists because the techniques have provided overwhelming evidence of the antiquity of the earth and life. Some so-called creation scientists have attempted to show that radiometric dating does not work on theoretical grounds for example, Arndts and Overn ; Gill but such attempts invariably have fatal flaws see Dalrymple ; York and Dalrymple Other creationists have focused on instances in which radiometric dating seems to yield incorrect results.
In most instances, these efforts are flawed because the authors have misunderstood or misrepresented the data they attempt to analyze for example, Woodmorappe ; Morris HM ; Morris JD Only rarely does a creationist actually find an incorrect radiometric result Austin ; Rugg and Austin that has not already been revealed and discussed in the scientific literature. 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 —10 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 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.
Decay routes[ edit ] The above uranium to lead decay routes occur via a series of alpha and beta decays, in which U with daughter nuclides undergo total eight alpha and six beta decays whereas U with daughters only experience seven alpha and four beta decays. The term U—Pb dating normally implies the coupled use of both decay schemes in the ‘concordia diagram’ see below. However, use of a single decay scheme usually U to Pb leads to the U—Pb isochron dating method, analogous to the rubidium—strontium dating method.
Finally, ages can also be determined from the U—Pb system by analysis of Pb isotope ratios alone.
The oldest rocks on Earth, found in western Greenland, have been dated by four independent radiometric dating methods at billion years. Rocks billion years in age have been found in southern Africa, western Australia, and the Great Lakes region of North America.
The Radiometric Dating Game Radiometric dating methods estimate the age of rocks using calculations based on the decay rates of radioactive elements such as uranium, strontium, and potassium. On the surface, radiometric dating methods appear to give powerful support to the statement that life has existed on the earth for hundreds of millions, even billions, of years. We are told that these methods are accurate to a few percent, and that there are many different methods. We are told that of all the radiometric dates that are measured, only a few percent are anomalous.
This gives us the impression that all but a small percentage of the dates computed by radiometric methods agree with the assumed ages of the rocks in which they are found, and that all of these various methods almost always give ages that agree with each other to within a few percentage points. Since there doesn’t seem to be any systematic error that could cause so many methods to agree with each other so often, it seems that there is no other rational conclusion than to accept these dates as accurate.
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 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.
How Science Figured Out the Age of Earth
Reliability of creationist sources Dr. Plaisted responds to comments and criticisms of this article here. On the surface, radiometric dating methods appear to give powerful support to the statement that life has existed on the earth for hundreds of millions, even billions, of years. We are told that these methods are accurate to a few percent, and that there are many different methods.
We are told that of all the radiometric dates that are measured, only a few percent are anomalous.
Uranium-Lead dating – why older dates are about million years based on the age of earth is the approximate age. So how long earth can precisely date the isochron will present a rock and to determine the age of the exact age of the science.
However, these excessively long ages are easily explained within the biblical worldview, and 14C actually presents a serious problem for believers in an old earth. Nearly anyone can verify this for themselves using basic multiplication and division. Any carbon atom has six protons within its nucleus, but the different isotopes have different numbers of neutrons.
Cosmic rays mainly high-energy protons trigger a process in the atmosphere that changes atmospheric nitrogen into 14C. However, unlike the other two carbon isotopes, 14C is unstable and eventually decays back into nitrogen. The decay rate can be measured for a large number of these 14C atoms. Since this decay process slows as the number of 14C atoms decreases, it may be expressed best in terms of a half-life, which is the amount of time for half of any given sample of 14C to decay back into nitrogen.
Thus, after one half-life, 50 percent of the original 14C atoms will remain. After two half-lives, 25 percent of the original 14C will remain, and so on. Once they die, however, organisms no longer take in new carbon, and the amount of 14C in their bodies begins to decrease. But the calculated dates will only be accurate if the assumptions behind the method are correct.