Brent Dalrymple



G. Brent Dalrymple (born May 9, 1937) is an American geologist, author of The Age of the Earth and Ancient Earth, Ancient Skies, and a National Medal of Science winner.

The Age of the Earth (1991)
All quotes from the trade paperback edition published in 1991 by Stanford University Press, ISBN 0-8047-2331-1 (1994 printing)


 * I was not overly enthusiastic about appearing in court. The goal of both the courts and science is to discover the truth, but the methods of the two are so different that it is difficult for most scientists to enter the legal arena with any degree of confidence. Finally, there was a natural reluctance, common to most scientists, to spend any time dealing with nonsense; the tenets of “scientific” creationism are so absurd that it seems most appropriate simply to ignore them.
 * Preface (p. viii)


 * The creationist “scientific” arguments for a young Earth are absurd, I and other authors have dealt with them at length elsewhere, and they do not merit further attention here.
 * Preface (p. x)


 * Estimates of the age of the Earth made prior to about 1950, biblical or otherwise, are all wrong, because they were based on methods now known to be invalid.
 * Chapter 2, “Early Attempts: A Variety of Approaches” (p. 18)


 * Biblical chronologies are historically important, but their credibility began to erode in the eighteenth and nineteenth centuries when it became apparent to some that it would be more profitable to seek a realistic age for the Earth through observation of nature than through a literal interpretation of parables. Today, scientists and biblical scholars alike agree that science is the proper arena in which to seek the numerical age of the Earth.
 * Chapter 2, “Early Attempts: A Variety of Approaches” (p. 23)


 * Invoking unique, supernatural, or extraordinary causes to explain natural history was to Buffon both unnecessary and unproductive.
 * Chapter 2, “Early Attempts: A Variety of Approaches” (p. 31)


 * If two or more radiometric clocks running at different rates give the same age, this is powerful evidence that the ages are correct.
 * Chapter 3, “Modern Radiometric Methods: How They Work” (p. 124)


 * There is incontrovertible evidence from lead-isotopic data that meteorites are approximately 4.55 ± 0.02 Ga. We can presume, as the evidence indicates, that the solid bodies of the Solar System formed nearly simultaneously, and conclude that the Pb-Pb age of meteorites also represents the age of Earth.
 * Chapter 7, “Isotopes of Lead: The Hourglass of the Solar System” (p. 332)


 * These calculations result in ages for the Earth of 4.52 to 4.56 Ga. Probably the best value is 4.54 Ga, found by (Fouad) Tera using the congruency point of the four oldest conformable lead ores. Its value, which is known to within 1% or better, is consistent with the ages of meteorites, the ages of the oldest lunar samples, and the ages of the oldest Earth rocks.
 * Chapter 7, “Isotopes of Lead: The Hourglass of the Solar System” (p. 356)


 * Our current understanding of the chronology of the universe, Galaxy, and Solar System represents the fulfillment of a quest that required more than two centuries of endeavor and surely is one of the most notable and spectacular achievements of modern science.
 * Chapter 9, “What We Know and Do Not Know” (p. 404)