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Line 1: − [[File:Blue Marble.jpg|thumbnail|200px|right|The historical and scientific evidence strongly indicates that the [[earth]] is approximately 6,000 years old.<ref>+ − *[http://creation.com/age-of-the-earth Age of the earth: 101 evidences for a young age of the earth and the universe]+ − *[http://creation.com/how-old-is-the-earth How old is the earth?]+ − *[http://creation.com/young-age-of-the-earth-universe-qa ‘Young’ age of the Earth & Universe Q&A]+ − *[http://creation.com/jesus-age-earth Jesus on the age of the earth]</ref>]]+ − ''See also [[Counterexamples to an Old Earth]].''+ + + + + + + + + + + + + + − The '''Age of the Earth''' has been a matter of interest to humans for millennia. All verifiable evidence indicates that the Earth is only about 6,000 years old. Yet with circular reasoning and implausible assumptions, [[liberals]] insist that the Earth is approximately 4.54 billion years (4.54 × 10<sup>9</sup> ± 1%).<ref>[http://www.interacademies.net/10878/13901.aspx] [http://www.cbsnews.com/stories/2005/10/22/opinion/polls/main965223.shtml polling]</ref>+ + + − Old Earth advocates rely on one flawed assumption to the exclusion of other evidence, similar to how an investigator may mistakenly rely on one faulty eyewitness's opinion to the exclusion of all else. In fact, eyewitness testimony is proven to be less reliable to than other indicators, just as the assumption by Old Earth proponents that the [[Radiometric dating|rate of radioactive decay]] has always been constant is flawed. In fact, The rate of radioactive decay would slow down greatly as the universe cools. Moreover, a large number of physical processes, such as neutron capture and fluctuations in solar radiation, affect the rate of radioactive decay of elements in the Earth's crust and render radioactive dating measurements unreliable, depending upon the specific methods used.<ref>http://www.sciencedirect.com/science/article/pii/S0899536205000138#bib6</ref> Even so, such an error will not cause a calculation of the age of the Earth based on radiometric dating to be off by up to five [[order of magnitude|orders of magnitude]].+ − Much scientific evidence [[young earth creationism|points to a young age of the earth and the universe]], and the biblical creation organization [[Creation Ministries International]] published articles entitled ''[http://creation.com/age-of-the-earth 101 evidences for a young age of the earth and the universe]'' and [http://creation.com/how-old-is-the-earth How old is the earth?] which summarize some of the evidence for a young age of the earth. + − == Historical views ==+ − [[Image:Landscape.jpg|right|300px]] − === Widespread Historical Acceptance of Biblical Account === − For most of recorded history humans of many backgrounds, such as St. Barnabas and St. Irenæus,<ref>Burnet, p. 259.</ref> viewed the age of the Earth to be around 6,000 years.<ref>Burnet, p. 258.</ref> − Saint [[Cyril]], who came into Great Moravia (present day [[Slovakia]] and Moravia in [[Czech Republic]]) from [[Byzantine Empire]] in 863 [[AD]] as Christian [[missionary]], wrote in his poem ''Proglas'',<ref>{{cite web+ − |title=Proglas − |publisher=sme.sk − |url=http://zlatyfond.sme.sk/dielo/93/Filozof_Proglas − |language=Slovak − |access date=05.05.2012 − |quote=The parchment version of Proglas in Cyrillic from 13th century was discovered in 1858 by Russian Slavic scholar Hilferding}}</ref> dedicated to his works on translation of the four [[Bible|biblical]] [[Gospel]]s to Slavonic language, the following sentence that brings testimony about the perception of the age of the world that time: − {| class="wikitable" − | rowspan="4" |{{cquote|To the holy Gospels I am the Foreword:<br/> for as it was promised by the prophets long ago,<br/> Christ comes to gather the nations,<br/> for He sheds light on the world entire.<br/>That is what has happened ''in our '''seventh''' millennium.''}} − !''The seventh millennium'' since the [[Creation]] was calculated as follows: − |- − | '''5 508''' years that had passed since the Creation till [[Jesus Christ]]’s birth plus − |- − | '''863''' (the year when Constantine and Methodius had come to Moravia) − |- − |results in figure of '''6 371'''.<ref>{{cite web|title=Proglas, the foreword to the Old Church Slavonic translation of the four Gospels|publisher=The Centre for Information on Literature, Slovakia|url=http://www.litcentrum.sk/36106|access date=05.05.2012|quote=Explanations: '''in our seventh millennium''' – it means the seventh millennium since the Creation. It was calculated as follows: 5 508 years that had passed since the Creation till Jesus Christ’s birth plus 863 AD (the year when Constantine and Methodius had come to Moravia) added to the year 6 371 -- that is seventh millennium.}}</ref> − |} − Prior to the onset of [[totalitarian]] and [[uniformitarianism |uniformitarian]] (i.e. long-age) [[scientism]] promoted by [[Charles Lyell|Lyell]], [[Darwin]], [[T. H. Huxley|Huxley]], and others in the 19th century, when most people and scientists in [[Europe]] and [[North America]] had a [[Christian]] or [[biblical]] worldview, the [[atheist]]ic [[evolution]]ary concept of billions of years for the age of the earth was unknown to mainstream [[Western civilization|Western]] [[science]] beyond cursory [[philosophical]] speculations.<ref name="YECBritannica">{{cite web |title=Encyclopaedia Britannica: supporting a young earth! |publisher=creation.com |url=http://creation.com/encyclopedia-britannica-supporting-a-young-earth |quote=The concept of billions of years for the age of the earth was unknown to science (or to the church[4]) before the rise of uniformitarianism in the 19th century. This is strong evidence that modern long-age views of creation do not originate in Genesis, but are a misguided attempt by some Christian leaders to try to reconcile what God has said with the atheistic pronouncements of evolutionary ‘science’.|accessdate=November 8, 2014}}</ref> − For example, in his 1619 book the ''Harmonices Mundi'' (The Harmony of the World), [[Johannes Kepler]], [[mathematician]] and [[astronomer]], wrote that he does not care if his book will need to wait a century for a reader, as [[God]] has waited '''six thousand years''' for him as an [[Scientific observation|observer]].<ref>{{cite book |title=The Harmony of the World |author=Johannes Kepler |publisher=American Philosophical Society |year=1997 |pages=IX, XXXVII, 391, 410 |url=http://books.google.com/books?id=rEkLAAAAIAAJ&q=six+thousand#v=snippet&q=six%20thousand&f=false|quote=O, Almighty God, I am thinking Thy thoughts after Thee! ... The book is written, to be read either now or by posterity, I care not which. It may be well to wait a century for a reader, as God has waited six thousand years for an observer.}}</ref><br> + + + + + + + + + + + + + + + + − In 1771, the first edition of the Encyclopædia Britannica, the oldest English-language general encyclopedia that was first published as a 3-volume set in Scotland, included a table of world events under the heading ‘Astronomy’ on page 493. These events begin with the [[creation]] of the world in the year 0, which they dated at 4007 years before Christ.<ref name="YECBritannica"/><ref>{{cite web |title= Encyclopaedia Britannica: supporting a young earth! |publisher= creation.com |url=http://creation.com/media-center?fileID=Rj4PFM_od9U |quote= The notion that the world in billions of years old has only been popular for about 200 years. Before that time most scientists understood that Noah's Flood was responsible for laying down the rocks which today are associated with millions of years. Richard Fangrad and Calvin Smith discuss the details. |accessdate=November 8, 2014}}</ref><br>+ + + + − In 1830, Dr. Hales published a list of 120 historical authorities from various cultures who had decided on an official [[date of creation]]. These ranged from 6984 B.C. to 3616 B.C.<ref>Batten 2002 quotes from "Young’s Analytical Concordance of the Holy Bible", 1879 8th Edition, 1939, which relates this, and reproduces the selection of the dates from Young.</ref>+ − Included in Hales' list is [[James Ussher]], who calculated the '''famous date of 4004 B.C.''' for creation. Young Earth creationists still consider this date to be close to the actual date.+ − === Evolutionists vs. Kelvin ===+ − − |author=E.J. Larson − |title=Evolution: The Remarkable History of a Scientific Theory − |publisher=Modern Library − |location=New York − |year=2006 − |pages=13-18, 39 − |isbn=0-8129-6849-2 − |url=http://books.google.no/books?id=xzLRvxlJhzkC&printsec=frontcover&dq=Larson+Evolution:+The+Remarkable+History&hl=en&sa=X&ei=PbZfVJugD83vaJengLgI&redir_esc=y#v=onepage&q=rejected%20Christianity%20&f=false}}</ref>, proposed that the Earth was about 74,832 years old.<ref name="ingv">INGV</ref> − [[James Hutton]], while not proposing a date, dismissed the Biblical account and claimed in 1785 that there was not evidence of a beginning at all.<ref name="ingv" /> − [[Charles Lyell]] supported Hutton's idea in 1830, in ''Principles of Geology''.<ref name="ingv" /> − + − Around the same time [[Lord Kelvin]] put his mind to deriving an age, and came up with a range between 20 million years and 400 million years. He later refined that down to between 20 million and 40 million years.<ref name="ingv" /> More recent discoveries of radioactivity and mantle convection explain why the assumptions Helmholtz and Kelvin made resulted in dates that are much lower than current uniformitarian estimates.+ + + − The 1911 edition of the [[Encyclopedia Britannica]] discussed dates up to 500 million years.<ref>Encyclopædia Britannica, pp 650-651.</ref>+ − By about 1930, J. H. Jeans was arguing for an age of the Earth of around two billion years.<ref>Universal History of the World, p.76.</ref>+ − === The Scientific Dogma of 4.5 billion years ===+ − − When in 1972 N.H. Gale tried to corroborate this established figure, he discovered that U-Pb ages ''"showed apparent large excess of radiogenic lead compared with the amount expected from the decay of Uranium in the meteorites over 4.5AE. ... For each of the 4 meteorites there was an excess of radiogenic lead not supported by uranium decay over 4.5AE.”'' After short analysis: + − *''“The superior modern analytical methods used made it impossible that analytical contamination could explain the result.'' − *''The circumstances ... make it extremely unlikely that terrestrial contamination could explain the results for this meteorites.'' − *''... a considerable excess of radiogenic lead in most fractions ...is difficult to attribute to contamination,“'' − rather than starting to reckon with possibility to challenge the established figures and methods, after recalling that ''“Patterson was the first to show that several stony meteorites yield a ... model of 4.5AE,”'' he proposed the new explanation for discovered discrepancy: ''"discordant results can be attributed to contamination."'' Consequently, his research of the Earth’s age turned into calculation of ''"the correct sample ratios"'' from ''"observed ratios"'' so that the Table in his paper could finally show the “correct” preconceived age, established in this field of research.<ref name=GALE>{{cite web |title=U-Pb studies of the appley bridge meteorite |author=Gale, N.H., Arden, J. and Hutchison, R. |publisher=Nature Phys. Science |year=1972 |volume=240 57 |url=http://www.springerlink.com/content/r741164v5162r447}}</ref> − Using [[circular logic]] -- assuming that decay rates remained constant despite necessarily changing physical characteristics as time approached the origin -- Old Earth proponents insist that the Earth is 4.5 billion years old based on an assumption of constancy in [[Potassium-argon dating|Potassium-argon (K:Ar) decay rates]] and other radiometric methods.<ref>Peck, 2000, p.376.</ref>+ + + + − In 1978, ''Geotimes'' magazine published by American Geological Institute quoted John Eddy, a famous astronomer, who argued that due to ''“some new and unexpected results“'' scientists could live with bishop Ussher’s 4004 B.C. value for the age of Earth and Sun, a fortiori since there is not much in the way of [[Scientific observation|observational]] [[Scientific evidence|evidence]] in [[astronomy]] to conflict with his calculations.<ref>{{cite journal |author=John Eddy quoted by R.G. Kazmann |title= It’s About Time: 4.5 Billion Years (report on Symposium at Louisiana State University)|publisher= Geotimes magazine (from 09/2008 renamed to Earth magazine) of American Geological Institute |year=1978 |issue=23 |pages=18-20|quote=I suspect that the Sun is 4.5 billion years old. However, given some new and unexpected results to the contrary, and some time for some frantic recalculation and theoretical readjustment, I suspect that we could live with bishop Ussher’s value for the age of Earth and Sun. I don’t think we have much in the way of observational evidence in astronomy to conflict with that.}}</ref><ref>{{cite web |author=Jon Covey |title= Age of the Universe |publisher= Creation In The Crossfire |date= January 3, 2013 |url=http://www.creationinthecrossfire.com/documents/AgeOfUniverse/AgeOfTheUniverse.html |accessdate=December 30, 2014 |quote= Evolutionary astronomers confidently argue the universe is 12-20 billion years old, although there is no certainty about any astronomical observations. John Eddy, a famous astronomer, once said that there isn’t much in the way of observational astronomy that proves the universe is old. He said that with “frantic theoretical readjustment” if new evidence showed that astronomers have been wrong, they could live with Bishop Ussher’s date of 4,004 B.C.}}</ref>+ + − == Geology ==+ − [[Image:516XZRGNCKL AA240 .jpg|right|300px]]+ − [[William R. Corliss]] is a cataloger of scientific [[Anomaly|anomalies]] (observations and facts that challenge prevailing scientific [[paradigm]]s) and has published many works on the subject.<ref name="sf">[http://www.science-frontiers.com/ Science Frontiers] (Corliss' web-site)</ref> + − He also wrote 13 books for the [[National Aeronautics and Space Administration]] (NASA), a dozen educational booklets for the [[Atomic Energy Commission]] (AEC), and a dozen articles for the [[National Science Foundation]] (NSF).<ref>Corliss, 2002</ref> The science magazine ''[[New Scientist]]'' had an article which focused on the career of William Corliss.<ref>Adrian Hope, ''Finding a Home for Stray Fact'', New Scientist, July 14, 1977, p. 83</ref>+ − ''New Scientist'' wrote regarding Corliss's work: "All I can say to Corliss is carry on cataloging". <ref>Quoted on the [http://www.science-frontiers.com/sourcebk.htm Science Frontiers web-site]</ref> [[Arthur C. Clarke]] described Corliss as "[[Charles Fort|Fort]]'s latter-day - and much more scientific - successor."<ref>Clarke, Arthur C. (1990) ''Astounding Days: A Science Fictional Autobiography''. Gollancz. Page 110</ref> − Corliss's work on geological anomalies catalogs scores of anomalies which challenge the [[old-earth]] [[paradigm]].<ref>[http://www.science-frontiers.com/sourcebk.htm#Geology Geological Catalogs] (Science Frontiers)</ref>+ + − == Bibliography ==+ − * Burnet, Thomas, [http://www.sacred-texts.com/earth/ste/ste36.htm The Sacred Theory of the Earth, chapter V], 1691. − * Encyclopedia Britannica, 11th edition (1911). [http://en.wikisource.org/wiki/User:Tim_Starling On-line page facsimiles]. − * Hammerton, J.A. (Ed.), "Universal History of the World" (8 volumes) The Educational Book Co., London, c1930. − * Batten, Don, [http://www.creationontheweb.com/content/view/417 Old-earth or young-earth belief: Which belief is the recent aberration?], ''Creation'' 24(1):24–27, December 2001. − * [http://www.ingv.it/~roma/SITOINGLESE/activities/geomagnetismo/analysistheory/historicalresearch/age.html The age of the Earth] (Istituto Nazionale di Geofisica e Vulcanologia (INGV)). − *Peck WH, Valley JW, Wilde SA, and Graham CM (2000) Ion microprobe Evidence for Pre-4.4 Ga Continental Crust and Low Temperature Water/Rock Interaction. ''Geol. Soc. Am. Abstr'', vol 32, no. 7. − == External Links ==+ − *[http://creation.com/age-of-the-earth Age of the earth] by [[Creation Ministries International]] − *[http://creation.com/refuting-evolution-chapter-8-how-old-is-the-earth How old is the earth?] - ''Refuting evolution'' - Chapter 8 by Dr. [[Jonathan Sarfati]] at [[Creation Ministries International]] − *[http://creation.com/young-age-of-the-earth-universe-qa Age of the Earth and Universe] by [[Creation Ministries International]] − + − <references />+ − + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
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Age of the Earth
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This article is about the scientific age of the Earth. For religious beliefs, see dating creation.
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The age of the Earth is 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%).[1][2][3] This age is based on evidence from radiometric age dating of meteorite material and is consistent with the ages of the oldest-known terrestrial and lunar samples.
Following the scientific revolution and the development of radiometric age dating, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.[4] The oldest such minerals analyzed to date – small crystals of zircon from the Jack Hills of Western Australia – are at least 4.404 billion years old.[5][6][7] Comparing the mass and luminosity of the Sun to those of other stars, it appears that the solar system cannot be much older than those rocks. Calcium-aluminium-rich inclusions – the oldest known solid constituents within meteorites that are formed within the Solar System – are 4.567 billion years old,[8][9] giving an age for the solar system and an upper limit for the age of Earth.
It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites. Because the exact amount of time this accretion process took is not yet known, and the predictions from different accretion models range from a few millions up to about 100 million years, the exact age of Earth is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
Contents
1 Development of modern geologic concepts
2 Early calculations
3 Radiometric dating
3.1 Overview
3.2 Convective mantle and radioactivity
3.3 Invention of radiometric dating
3.4 Arthur Holmes establishes radiometric dating
3.5 Modern radiometric dating
3.5.1 Why meteorites were used
3.5.2 Canyon Diablo meteorite
3.6 Helioseismic verification
4 See also
5 References
6 Bibliography
7 Further reading
8 External links
Development of modern geologic concepts
Main article: History of geology
Further information: Relative dating
Earth as seen from Apollo 17
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.[10][11]
Nicolas Steno in the 17th century was one of the first naturalists to appreciate the connection between fossil remains and strata.[11] His observations led him to formulate important stratigraphic concepts (i.e., the "law of superposition" and the "principle of original horizontality").[12] In the 1790s, William Smith hypothesized that if two layers of rock at widely differing locations contained similar fossils, then it was very plausible that the layers were the same age.[13] William Smith's nephew and student, John Phillips, later calculated by such means that Earth was about 96 million years old.[14]
The naturalist Mikhail Lomonosov suggested in the mid-18th century that Earth had been created separately from the rest of the universe, several hundred thousand years before. Lomonosov's ideas were mostly speculative. In 1779 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 75,000 years old.
In 1778 George-Louis Lecrerc, Count of [[Buffon]], who rejected [[Christianity]], adopted [[Evolutionism|evolutionary thought]] and thus searched for [[materialistic]] explanations for the origin of earth<ref name="Larson">{{cite book
In 1854 [[Hermann von Helmholtz]] estimated an age of between 20 and 40 million years.<ref name="ingv" />
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. In 1830, geologist Charles Lyell, developing ideas found in James Hutton's works, popularized the concept that the features of Earth were in perpetual change, eroding and reforming continuously, and the rate of this change was roughly constant. This was a challenge to the traditional view, which saw the history of Earth as static, with changes brought about by intermittent catastrophes. Many naturalists were influenced by Lyell to become "uniformitarians" who believed that changes were constant and uniform.
Early calculations
William Thomson (Lord Kelvin)
Further information: William Thomson, 1st Baron Kelvin § Age of the Earth: geology and theology
In 1862, the physicist William Thomson published calculations that fixed the age of Earth at between 20 million and 400 million years.[15][16] He assumed that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface to cool to its present temperature. His calculations did not account for heat produced via radioactive decay (a process then unknown to science) or convection inside the Earth, which allows more heat to escape from the interior to warm rocks near the surface.[15]
Geologists such as Charles Lyell had trouble accepting such a short age for Earth. For biologists, even 100 million years seemed much too short to be plausible. In Darwin's theory of evolution, the process of random heritable variation with cumulative selection requires great durations of time. (Modern geneticists have measured the rate of genetic divergence of species, using the molecular clock, to date the last universal ancestor of all living organisms no later than 3.5 to 3.8 billion years ago).
In a lecture in 1869, Darwin's great advocate, Thomas H. Huxley, attacked Thomson's calculations, suggesting they appeared precise in themselves but were based on faulty assumptions. The physicist Hermann von Helmholtz (in 1856) and astronomer Simon Newcomb (in 1892) contributed their own calculations of 22 and 18 million years respectively to the debate: they independently calculated the amount of time it would take for the Sun to condense down to its current diameter and brightness from the nebula of gas and dust from which it was born.[17] Their values were consistent with Thomson's calculations. However, they assumed that the Sun was only glowing from the heat of its gravitational contraction. The process of solar nuclear fusion was not yet known to science.
In his 1956 paper named ''Age of Meteorites and the Earth'', Claire Patterson, using ''“certain assumptions which are apparently justified,”'' introduced for meteor age a figure of '''4.55 ±0.07 × 10<sup>9</sup>yr.''' and commented that since earth lead meets the requirement for definition of ''“the isotopic evolution of lead for any meteoritic body,”'' it is therefore ''“believed that the age for the earth is the same as for meteorites”'' and that ''"this is the time since the earth attained its present mass"''.<ref>{{cite web |title= Age of meteorites and the earth |author= Claire Patterson |url=http://www.mantleplumes.org/WebDocuments/Patterson1956.pdf |accessdate= }}</ref> In spite of cautions and skepticism advised by the authors, this figure gradually became a scientific dogma that rarely anyone has dared to question.<ref>{{cite journal |author=Ralph W. Matthews |title=Radiometric dating and the age of the Earth |date=December 1982 |publisher=Creation |volume=5 |issue=1 |pages=41–44 |quote=In spite of cautions and skepticism advised by the authors this number has been widely and enthusiastically accepted and is usually quoted as if the evidence was decisive and conclusive. It has assumed something of the status of a universal constant to which all other data must be fitted, thus it has become common practice to assume that data which does not fit this result is either wrong or unintelligible. |accessdate=December 30, 2014}}</ref> Henry Morris explains that the unprovable assumptions are not the only problem with radiometric dating. One huge concern is that the results published are only a selected sample, chosen especially to agree with preconceived ideas about the earth, life, and [[evolution]].<ref>{{cite web |title=Once upon a time … A Review of The Mythology of Modern Dating Methods by John Woodmorappe |author=Michael J. Oard |url=http://creation.com/once-upon-a-time |accessdate=November 9, 2014}}</ref>
Other scientists backed up Thomson's figures as well. Charles Darwin's son, the astronomer George H. Darwin, proposed that Earth and Moon had broken apart in their early days when they were both molten. He calculated the amount of time it would have taken for tidal friction to give Earth its current 24-hour day. His value of 56 million years added additional evidence that Thomson was on the right track.[17]
The last estimate Thomson gave, in 1897, was: "that it was more than 20 and less than 40 million year old, and probably much nearer 20 than 40".[18] In 1899 and 1900, John Joly calculated the rate at which the oceans should have accumulated salt from erosion processes, and determined that the oceans were about 80 to 100 million years old.[17]
Radiometric dating
Main article: Radiometric dating
Overview
By their chemical nature, rock minerals contain certain elements and not others; but in rocks containing radioactive isotopes, the process of radioactive decay generates exotic elements over time. By measuring the concentration of the stable end product of the decay, coupled with knowledge of the half life and initial concentration of the decaying element, the age of the rock can be calculated.[19] Typical radioactive end products are argon from decay of potassium-40, and lead from decay of uranium and thorium.[19] If the rock becomes molten, as happens in Earth's mantle, such nonradioactive end products typically escape or are redistributed.[19] Thus the age of the oldest terrestrial rock gives a minimum for the age of Earth, assuming that no rock has been intact for longer than the Earth itself.
Convective mantle and radioactivity
In 1892, Thomson had been made Lord Kelvin in appreciation of his many scientific accomplishments. Kelvin calculated the age of Earth by using thermal gradients, and arrived at an estimate of 100 million years old.[20] He did not realize that Earth has a highly viscous fluid mantle, and this invalidated his estimate. In 1895, John Perry produced an age-of-Earth estimate of 2 to 3 billion years using a model of a convective mantle and thin crust.[20] Kelvin stuck by his estimate of 100 million years, and later reduced it to about 20 million years.
The discovery of radioactivity introduced another factor in the calculation. After Henri Becquerel's initial discovery in 1896, Marie and Pierre Curie discovered the radioactive elements polonium and radium in 1898; and in 1903, Pierre Curie and Albert Laborde announced that radium produces enough heat to melt its own weight in ice in less than an hour. Geologists quickly realized that this upset the assumptions underlying most calculations of the age of Earth. These had assumed that the original heat of the Earth and Sun had dissipated steadily into space, but radioactive decay meant that this heat had been continually replenished. George Darwin and John Joly were the first to point this out, in 1903.[21]
Invention of radiometric dating
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2012)
Radioactivity, which had overthrown the old calculations, yielded a bonus by providing a basis for new calculations, in the form of radiometric dating.
Ernest Rutherford in 1908.
Ernest Rutherford and Frederick Soddy jointly had continued their work on radioactive materials and concluded that radioactivity was due to a spontaneous transmutation of atomic elements. In radioactive decay, an element breaks down into another, lighter element, releasing alpha, beta, or gamma radiation in the process. They also determined that a particular isotope of a radioactive element decays into another element at a distinctive rate. This rate is given in terms of a "half-life", or the amount of time it takes half of a mass of that radioactive material to break down into its "decay product".
Some radioactive materials have short half-lives; some have long half-lives. Uranium and thorium have long half-lives, and so persist in Earth's crust, but radioactive elements with short half-lives have generally disappeared. This suggested that it might be possible to measure the age of Earth by determining the relative proportions of radioactive materials in geological samples. In reality, radioactive elements do not always decay into nonradioactive ("stable") elements directly, instead, decaying into other radioactive elements that have their own half-lives and so on, until they reach a stable element. Such "decay series", such as the uranium-radium and thorium series, were known within a few years of the discovery of radioactivity, and provided a basis for constructing techniques of radiometric dating.
== Notes ==
The pioneers of radioactivity were chemist Bertram B. Boltwood and the energetic Rutherford. Boltwood had conducted studies of radioactive materials as a consultant, and when Rutherford lectured at Yale in 1904,[22] Boltwood was inspired to describe the relationships between elements in various decay series. Late in 1904, Rutherford took the first step toward radiometric dating by suggesting that the alpha particles released by radioactive decay could be trapped in a rocky material as helium atoms. At the time, Rutherford was only guessing at the relationship between alpha particles and helium atoms, but he would prove the connection four years later.
[[Category:Geology]]
Soddy and Sir William Ramsay had just determined the rate at which radium produces alpha particles, and Rutherford proposed that he could determine the age of a rock sample by measuring its concentration of helium. He dated a rock in his possession to an age of 40 million years by this technique. Rutherford wrote,
I came into the room, which was half dark, and presently spotted Lord Kelvin in the audience and realized that I was in trouble at the last part of my speech dealing with the age of the Earth, where my views conflicted with his. To my relief, Kelvin fell fast asleep, but as I came to the important point, I saw the old bird sit up, open an eye, and cock a baleful glance at me! Then a sudden inspiration came, and I said, 'Lord Kelvin had limited the age of the Earth, provided no new source was discovered. That prophetic utterance refers to what we are now considering tonight, radium!' Behold! the old boy beamed upon me.[23]
Rutherford assumed that the rate of decay of radium as determined by Ramsay and Soddy was accurate, and that helium did not escape from the sample over time. Rutherford's scheme was inaccurate, but it was a useful first step.
Boltwood focused on the end products of decay series. In 1905, he suggested that lead was the final stable product of the decay of radium. It was already known that radium was an intermediate product of the decay of uranium. Rutherford joined in, outlining a decay process in which radium emitted five alpha particles through various intermediate products to end up with lead, and speculated that the radium-lead decay chain could be used to date rock samples. Boltwood did the legwork, and by the end of 1905 had provided dates for 26 separate rock samples, ranging from 92 to 570 million years. He did not publish these results, which was fortunate because they were flawed by measurement errors and poor estimates of the half-life of radium. Boltwood refined his work and finally published the results in 1907.[4]
Boltwood's paper pointed out that samples taken from comparable layers of strata had similar lead-to-uranium ratios, and that samples from older layers had a higher proportion of lead, except where there was evidence that lead had leached out of the sample. His studies were flawed by the fact that the decay series of thorium was not understood, which led to incorrect results for samples that contained both uranium and thorium. However, his calculations were far more accurate than any that had been performed to that time. Refinements in the technique would later give ages for Boltwood's 26 samples of 250 million to 1.3 billion years.
Arthur Holmes establishes radiometric dating
Although Boltwood published his paper in a prominent geological journal, the geological community had little interest in radioactivity. Boltwood gave up work on radiometric dating and went on to investigate other decay series. Rutherford remained mildly curious about the issue of the age of Earth but did little work on it.
Robert Strutt tinkered with Rutherford's helium method until 1910 and then ceased. However, Strutt's student Arthur Holmes became interested in radiometric dating and continued to work on it after everyone else had given up. Holmes focused on lead dating, because he regarded the helium method as unpromising. He performed measurements on rock samples and concluded in 1911 that the oldest (a sample from Ceylon) was about 1.6 billion years old.[24] These calculations were not particularly trustworthy. For example, he assumed that the samples had contained only uranium and no lead when they were formed.
More important research was published in 1913. It showed that elements generally exist in multiple variants with different masses, or "isotopes". In the 1930s, isotopes would be shown to have nuclei with differing numbers of the neutral particles known as "neutrons". In that same year, other research was published establishing the rules for radioactive decay, allowing more precise identification of decay series.
Many geologists felt these new discoveries made radiometric dating so complicated as to be worthless. Holmes felt that they gave him tools to improve his techniques, and he plodded ahead with his research, publishing before and after the First World War. His work was generally ignored until the 1920s, though in 1917 Joseph Barrell, a professor of geology at Yale, redrew geological history as it was understood at the time to conform to Holmes's findings in radiometric dating. Barrell's research determined that the layers of strata had not all been laid down at the same rate, and so current rates of geological change could not be used to provide accurate timelines of the history of Earth.
Holmes's persistence finally began to pay off in 1921, when the speakers at the yearly meeting of the British Association for the Advancement of Science came to a rough consensus that Earth was a few billion years old, and that radiometric dating was credible. Holmes published The Age of the Earth, an Introduction to Geological Ideas in 1927 in which he presented a range of 1.6 to 3.0 billion years. No great push to embrace radiometric dating followed, however, and the die-hards in the geological community stubbornly resisted. They had never cared for attempts by physicists to intrude in their domain, and had successfully ignored them so far. The growing weight of evidence finally tilted the balance in 1931, when the National Research Council of the US National Academy of Sciences decided to resolve the question of the age of Earth by appointing a committee to investigate. Holmes, being one of the few people on Earth who was trained in radiometric dating techniques, was a committee member, and in fact wrote most of the final report.[25]
The report concluded that radioactive dating was the only reliable means of pinning down geological time scales. Questions of bias were deflected by the great and exacting detail of the report. It described the methods used, the care with which measurements were made, and their error bars and limitations.
Modern radiometric dating
Radiometric dating continues to be the predominant way scientists date geologic timescales. Techniques for radioactive dating have been tested and fine-tuned for the past 50+ years. Forty or so different dating techniques have been utilized to date, working on a wide variety of materials. Dates for the same sample using these different techniques are in very close agreement on the age of the material.
Possible contamination problems do exist, but they have been studied and dealt with by careful investigation, leading to sample preparation procedures being minimized to limit the chance of contamination.
Why meteorites were used
An age of 4.55 ± 0.07 billion years, very close to today's accepted age, was determined by C.C. Patterson using uranium-lead isotope dating (specifically lead-lead dating) on several meteorites including the Canyon Diablo meteorite and published in 1956.[26]
Lead isotope isochron diagram showing data used by Patterson to determine the age of the Earth in 1956.
The quoted age of Earth is derived, in part, from the Canyon Diablo meteorite for several important reasons and is built upon a modern understanding of cosmochemistry built up over decades of research.
Most geological samples from Earth are unable to give a direct date of the formation of Earth from the solar nebula because Earth has undergone differentiation into the core, mantle, and crust, and this has then undergone a long history of mixing and unmixing of these sample reservoirs by plate tectonics, weathering and hydrothermal circulation.
All of these processes may adversely affect isotopic dating mechanisms because the sample cannot always be assumed to have remained as a closed system, by which it is meant that either the parent or daughter nuclide (a species of atom characterised by the number of neutrons and protons an atom contains) or an intermediate daughter nuclide may have been partially removed from the sample, which will skew the resulting isotopic date. To mitigate this effect it is usual to date several minerals in the same sample, to provide an isochron. Alternatively, more than one dating system may be used on a sample to check the date.
Some meteorites are furthermore considered to represent the primitive material from which the accreting solar disk was formed.[27] Some have behaved as closed systems (for some isotopic systems) soon after the solar disk and the planets formed. To date, these assumptions are supported by much scientific observation and repeated isotopic dates, and it is certainly a more robust hypothesis than that which assumes a terrestrial rock has retained its original composition.
Nevertheless, ancient Archaean lead ores of galena have been used to date the formation of Earth as these represent the earliest formed lead-only minerals on the planet and record the earliest homogeneous lead-lead isotope systems on the planet. These have returned age dates of 4.54 billion years with a precision of as little as 1% margin for error.[28]
Statistics for several meteorites that have undergone isochron dating are as follows:[29]
1. St. Severin (ordinary chondrite)
1. Pb-Pb isochron 4.543 ± 0.019 GY
2. Sm-Nd isochron 4.55 ± 0.33 GY
3. Rb-Sr isochron 4.51 ± 0.15 GY
4. Re-Os isochron 4.68 ± 0.15 GY
2. Juvinas (basaltic achondrite)
1. Pb-Pb isochron 4.556 ± 0.012 GY
2. Pb-Pb isochron 4.540 ± 0.001 GY
3. Sm-Nd isochron 4.56 ± 0.08 GY
4. Rb-Sr isochron 4.50 ± 0.07 GY
3. Allende (carbonaceous chondrite)
1. Pb-Pb isochron 4.553 ± 0.004 GY
2. Ar-Ar age spectrum 4.52 ± 0.02 GY
3. Ar-Ar age spectrum 4.55 ± 0.03 GY
4. Ar-Ar age spectrum 4.56 ± 0.05 GY
Canyon Diablo meteorite
Further information: Canyon Diablo (meteorite)
Fragment of the Canyon Diablo iron meteorite.
The Canyon Diablo meteorite was used because it is a very large representative of a particularly rare type of meteorite that contains sulfide minerals (particularly troilite, FeS), metallic nickel-iron alloys, plus silicate minerals.
Barringer Crater, Arizona where the Canyon Diablo meteorite was found.
This is important because the presence of the three mineral phases allows investigation of isotopic dates using samples that provide a great separation in concentrations between parent and daughter nuclides. This is particularly true of uranium and lead. Lead is strongly chalcophilic and is found in the sulfide at a much greater concentration than in the silicate, versus uranium. Because of this segregation in the parent and daughter nuclides during the formation of the meteorite, this allowed a much more precise date of the formation of the solar disk and hence the planets than ever before.
The age determined from the Canyon Diablo meteorite has been confirmed by hundreds of other age determinations, from both terrestrial samples and other meteorites.[30] The meteorite samples, however, show a spread from 4.53 to 4.58 billion years ago. This is interpreted as the duration of formation of the solar nebula and its collapse into the solar disk to form the Sun and the planets. This 50 million year time span allows for accretion of the planets from the original solar dust and meteorites.
The moon, as another extraterrestrial body that has not undergone plate tectonics and that has no atmosphere, provides quite precise age dates from the samples returned from the Apollo missions. Rocks returned from the Moon have been dated at a maximum of around 4.4 and 4.5 billion years old. Martian meteorites that have landed upon Earth have also been dated to around 4.5 billion years old by lead-lead dating. Lunar samples, since they have not been disturbed by weathering, plate tectonics or material moved by organisms, can also provide dating by direct electron microscope examination of cosmic ray tracks. The accumulation of dislocations generated by high energy cosmic ray particle impacts provides another confirmation of the isotopic dates. Cosmic ray dating is only useful on material that has not been melted, since melting erases the crystalline structure of the material, and wipes away the tracks left by the particles.
Altogether, the concordance of age dates of both the earliest terrestrial lead reservoirs and all other reservoirs within the Solar System found to date are used to support the hypothesis that Earth and the rest of the Solar System formed at around 4.53 to 4.58 billion years ago.
Helioseismic verification
The radiometric date of meteorites can be verified with studies of the Sun. The Sun can be dated using helioseismic methods that strongly agree with the radiometric dates found for the oldest meteorites.[31]
See also
Age of the universe
Geochronology
History of the Earth
Natural history
Oldest dated rocks
Radiometric dating
Timeline of natural history
References
"Age of the Earth". U.S. Geological Survey. 1997. Archived from the original on 23 December 2005. Retrieved 2006-01-10.
Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Special Publications, Geological Society of London 190 (1): 205–221. Bibcode:2001GSLSP.190..205D. doi:10.1144/GSL.SP.2001.190.01.14.
Manhesa, Gérard; Allègre, Claude J.; Dupréa, Bernard; and Hamelin, Bruno (1980). "Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics". Earth and Planetary Science Letters 47 (3): 370–382. Bibcode:1980E&PSL..47..370M. doi:10.1016/0012-821X(80)90024-2.
Boltwood, B. B. (1907). "On the ultimate disintegration products of the radio-active elements. Part II. The disintegration products of uranium". American Journal of Science 23 (134): 77–88. doi:10.2475/ajs.s4-23.134.78.
For the abstract, see: Chemical Abstracts Service, American Chemical Society (1907). Chemical Abstracts. New York, London: American Chemical Society. p. 817. Retrieved 2008-12-19.
Wilde, S. A.; Valley, J. W.; Peck, W. H.; Graham C. M. (2001-01-11). "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago". Nature 409 (6817): 175–178. doi:10.1038/35051550. PMID 11196637.
Valley, John W.; Peck, William H.; Kin, Elizabeth M. (1999). "Zircons Are Forever". The Outcrop, Geology Alumni Newsletter. University of Wisconsin-Madison. pp. 34–35. Retrieved 2008-12-22.
Wyche, S.; Nelson, D. R.; Riganti, A. (2004). "4350–3130 Ma detrital zircons in the Southern Cross Granite–Greenstone Terrane, Western Australia: implications for the early evolution of the Yilgarn Craton". Australian Journal of Earth Sciences 51 (1): 31–45. doi:10.1046/j.1400-0952.2003.01042.x.
Amelin, Y; Krot, An; Hutcheon, Id; Ulyanov, Aa (Sep 2002). "Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions". Science 297 (5587): 1678–83. Bibcode:2002Sci...297.1678A. doi:10.1126/science.1073950. ISSN 0036-8075. PMID 12215641.
Baker, J.; Bizzarro, M.; Wittig, N.; Connelly, J.; Haack, H. (2005-08-25). "Early planetesimal melting from an age of 4.5662 Gyr for differentiated meteorites". Nature 436 (7054): 1127–1131. Bibcode:2005Natur.436.1127B. doi:10.1038/nature03882. PMID 16121173.
Lyell, Charles, Sir (1866). Elements of Geology; or, The Ancient Changes of the Earth and its Inhabitants as Illustrated by Geological Monuments (Sixth ed.). New York: D. Appleton and company. Retrieved 2008-12-19.
Stiebing, William H. (1994). Uncovering the Past. Oxford University Press US. ISBN 0-19-508921-9.
Brookfield, Michael E. (2004). Principles of Stratigraphy. Blackwell Publishing. p. 116. ISBN 1-4051-1164-X.
Fuller, J. G. C. M. (2007-07-17). "Smith's other debt, John Strachey, William Smith and the strata of England 1719–1801". Geoscientist. The Geological Society. Archived from the original on 24 November 2008. Retrieved 2008-12-19.
Burchfield, Joe D. (1998). "The age of the Earth and the invention of geological time". Geological Society, London, Special Publications 143 (1): 137–143. Bibcode:1998GSLSP.143..137B. doi:10.1144/GSL.SP.1998.143.01.12.
England, P.; Molnar, P.; Righter, F. (January 2007). "John Perry's neglected critique of Kelvin's age for the Earth: A missed opportunity in geodynamics". GSA Today 17 (1): 4–9. doi:10.1130/GSAT01701A.1.
Dalrymple (1994) pp. 14–17, 38
Dalrymple (1994) pp. 14–17
Dalrymple (1994) pp. 14, 43
Nichols, Gary (2009). "21.2 Radiometric Dating". Sedimentology and Stratigraphy. John Wiley & Sons. pp. 325–327. ISBN 978-1405193795.
England, Philip C.; Molnar, Peter; Richter, Frank M. (2007). "Kelvin, Perry and the Age of the Earth". American Scientist 95 (4): 342–349. doi:10.1511/2007.66.3755.
Joly, John (1909). Radioactivity and Geology: An Account of the Influence of Radioactive Energy on Terrestrial History (1st ed.). London, UK: Archibald Constable & Co., ltd. p. 36. Reprinted by BookSurge Publishing (2004) ISBN 1-4021-3577-7.
Rutherford, E. (1906). Radioactive Transformations. London: Charles Scriber's Sons. Reprinted by Juniper Grove (2007) ISBN 978-1-60355-054-3.
Eve, Arthur Stewart (1939). Rutherford: Being the life and letters of the Rt. Hon. Lord Rutherford, O. M. Cambridge: Cambridge University Press.
Dalrymple (1994) p. 74
Dalrymple (1994) pp. 77–78
Patterson, Claire (1956). "Age of meteorites and the earth". Geochimica et Cosmochimica Acta 10 (4): 230–237. Bibcode:1956GeCoA..10..230P. doi:10.1016/0016-7037(56)90036-9. Retrieved 2009-07-07.
Carlson, R. W.; Tera, F. (December 1–3, 1998). "Conference Proceedings, Origin of the Earth and Moon". Houston, Texas: Lunar and Planetary Institute. p. 6. Archived from the original on 16 December 2008. Retrieved 2008-12-22. |chapter= ignored (help)
Dalrymple (1994) pp. 310–341
Dalrymple, Brent G. (2004). "Ancient Earth, Ancient Skies: The Age of the Earth and Its Cosmic Surroundings". Stanford University Press. pp. 147, 169. ISBN 978-0-8047-4933-6.
Terada, K.; Sano, Y. (May 20–24, 2001). "Proceedings, Eleventh Annual V. M. Goldschmidt Conference". Hot Springs, Virginia: Lunar and Planetary Institute. Bibcode:2001eag..conf.3306T. Archived from the original on 16 December 2008. Retrieved 2008-12-22. |chapter= ignored (help)
Bonanno, A.; Schlattl, H.; Paternò, L. (August 2002). "The age of the Sun and the relativistic corrections in the EOS". Astronomy and Astrophysics 390 (3): 1115–1118. arXiv:astro-ph/0204331. Bibcode:2002A&A...390.1115B. doi:10.1051/0004-6361:20020749.
Bibliography
Dalrymple, G. Brent (1994-02-01). The Age of the Earth. Stanford University Press. ISBN 0-8047-2331-1.
Further reading
Baadsgaard, H.; Lerbekmo, J.F.; Wijbrans, J.R., 1993. Multimethod radiometric age for a bentonite near the top of the Baculites reesidei Zone of southwestern Saskatchewan (Campanian-Maastrichtian stage boundary?). Canadian Journal of Earth Sciences, v.30, p. 769–775.
Baadsgaard, H. and Lerbekmo, J.F., 1988. A radiometric age for the Cretaceous-Tertiary boundary based on K-Ar, Rb-Sr, and U-Pb ages of bentonites from Alberta, Saskatchewan, and Montana. Canadian Journal of Earth Sciences, v.25, p. 1088–1097.
Eberth, D.A. and Braman, D., 1990. Stratigraphy, sedimentology, and vertebrate paleontology of the Judith River Formation (Campanian) near Muddy Lake, west-central Saskatchewan. Bulletin of Canadian Petroleum Geology, v.38, no.4, p. 387–406.
Goodwin, M.B. and Deino, A.L., 1989. The first radiometric ages from the Judith River Formation (Upper Cretaceous), Hill County, Montana. Canadian Journal of Earth Sciences, v.26, p. 1384–1391.
Gradstein, F. M.; Agterberg, F.P.; Ogg, J.G.; Hardenbol, J.; van Veen, P.; Thierry, J. and Zehui Huang., 1995. A Triassic, Jurassic and Cretaceous time scale. IN: Bergren, W. A. ; Kent, D.V.; Aubry, M-P. and Hardenbol, J. (eds.), Geochronology, Time Scales, and Global Stratigraphic Correlation. Society of Economic Paleontologists and Mineralogists, Special Publication No. 54, p. 95–126.
Harland, W.B., Cox, A.V.; Llewellyn, P.G.; Pickton, C.A.G.; Smith, A.G.; and Walters, R., 1982. A Geologic Time Scale: 1982 edition. Cambridge University Press: Cambridge, 131p.
Harland, W.B.; Armstrong, R.L.; Cox, A.V.; Craig, L.E.; Smith, A.G.; Smith, D.G., 1990. A Geologic Time Scale, 1989 edition. Cambridge University Press: Cambridge, p. 1–263. ISBN 0-521-38765-5
Harper, C.W., Jr., 1980. Relative age inference in paleontology. Lethaia, v. 13, p. 239–248.
Obradovich, J.D., 1993. A Cretaceous time scale. IN: Caldwell, W.G.E. and Kauffman, E.G. (eds.). Evolution of the Western Interior Basin. Geological Association of Canada, Special Paper 39, p. 379–396.
Palmer, Allison R. (compiler), 1983. The Decade of North American Geology 1983 Geologic Time Scale. Geology, v. 11, p. 503–504. September 12, 2004.
Powell, James Lawrence, 2001, Mysteries of Terra Firma: the Age and Evolution of the Earth, Simon & Schuster, ISBN 0-684-87282-X
External links
TalkOrigins.org
Vectorsite.net – Initial version of this article was based on a public domain text by Greg Goebel
USGS preface on the Age of the Earth
NASA exposition on the age of Martian meteorites
Ageing the Earth on In Our Time at the BBC. (listen now)
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