Customer Reviews

Nature's Clocks: How Scientists Measure the Age of Almost Everything

5 star:		(5)
4 star:		(1)
3 star:		(0)
2 star:		(0)
1 star:		(0)

 

 

The main focus of this book is on how objects can be dated using measurements of radioactive isotopes and their products, that is the elements and isotopes that form after radioactive decay.

The author begins with a brief discussion of ideas about the earth's duration before the advent of dating techniques using radioactive isotopes. Here he discusses the duration of the earth as inferred from the Bible, the influence of James Hutton in moving scientific opinion towards a longer time scale, William Smith's use of fossils to come to a relative (that is, the order in which rocks were formed, but not when they were formed) dating of sedimentary rocks, and the conflict in the later half of the 19th century between geologists' belief in a long earth history and the physicist Lord Kelvin's model of a relatively short (20 million years in some versions of the model) duration for the earth.

With the discovery of radioactivity, in the early 20th century it became apparent that radioactive decay could be used a sort of clock. The physicist Ernest Rutherford was one of the first to attempt to estimate geological time scales using radioactive decay. The British geologist Arthur Holmes in his early work was one of the first geologist's to use the decay of uranium to lead to estimate geological time scales. These early efforts were hampered by the lack of understanding that different isotopes of the same element exist, and that there can be more than one radioactive isotope of an element.

As understanding of the complexity of the problem increased, more accurate methods resulted. Claire Patterson, at the University of Chicago and later at Caltech, came up with the roughly 4.55 billion year estimate of the duration of the earth's existence in the 1950s using the uranium to lead decay series, after much difficulty in eliminating laboratory contamination of lead from leaded gasoline. Starting in the 1940s at the University of Chicago, Libby and his graduate students developed carbon 14 dating, which is suitable for dating objects that contain carbon from roughly the last 50,000 years and is therefore useful for archaeologists, and for geologists who study ice ages. One thing I was interested to learn is that the carbon 14 method is the only one that involves the actual counting of radioactive decay; the other methods, such as uranium to lead or potasssium argon, actually require the measurement of the "parent" element and isotope (such as uranium) and the "daughter" element and isotope (such as lead) with a mass spectrometer, because radioactive decay is too slow for practical counting from small samples of these isotopes.

Each radioactive method is suitable for different time spans, The uranium lead method is suitable for very long (billions, hundreds of millios of years) time spans, the potsssium argon method for intermediate (in a geological sense!) time spans, and carbon 14 for the last 50,000 years or so. Because carbon 14 is produced at varying rates over time in the upper atmosphere (from the interaction of cosmic radiation with molecules in the air), to improve its accuracy it is calibrated with (mainly) tree ring data. The calibration at the moment goes back about 26,000 years.

Recent developments have allowed for collecting information from smaller samples, such as individual crystals of zircon,

I found the book easy to read. The author includes two appendices with some discussion of the mathematics of radioactive decay, a chart of the geological time scale, and the periodic table of the chemical elements.

Nature's Clocks is about the history of dating the age of the earth, from Newton to Kelvin to Marie Curie and many other scientists who made important contributions to this subject. Though McDougall also lightly touches on other dating methods like tree rings, the bulk of the book deals with radiometric dating and carbon-14 dating and how it relates to geology, archaeology etc.

What makes this book an absolute gem are two things. Firstly, McDougall has interesting anecdotes about lots of discoveries and the scientists who discovered them - this really makes the subject come alive. Secondly, he makes difficult topics like radiometric dating accessible in layman-friendly terms, and in great detail.

Highly recommended to anyone interested in how the earth is dated.

This excellent book provides an overview of how things or events from the past can be dated - from when the earth formed to events in human history. As the author points out, although much of the distant past can be dated in a relative way, i.e., by classifying events in the order in which they occurred, the determination of actual ages has received an incredible boost through the use of radioactive isotopes of certain elements. The author weaves this fascinating tale very well - from the discovery of radioactivity, through the discovery of its use in dating ancient artifacts to refining the age of the earth and the timing of milestones in human evolution. The individuals who did the early pioneering work, as well as those who currently strive for greater precision and refinement in this field, play prominent roles in this gripping story which clearly illustrates how science works. The writing style is clear, friendly, authoritative, very engaging and quite accessible. This book appears to have been aimed at broad readership; specialized terminology is well explained when first used in the main text and a glossary of technical terms can be found at the back of the book. But also, an appendix is included that concentrates on some of the mathematical formulas involved, for those who are more mathematically/technically inclined. Consequently, this book can be enjoyed by anyone, although science buffs may consider it a particularly special treat.

This is a very nice discussion of the various techniques scientists use to date things. It starts with a review of the early concepts regarding the age of the earth. Then it discusses the discovery of radioactivity, radioactive isotopes, and the first attempts to use them to date rocks. Following this it describes in detail the invention of radiocarbon dating and its impact on archaeology and anthropology, followed by the invention of techniques for dating rocks, meterorites, and the earth, with applications to geology, paleontology, and evolution. Interesting links between radioisotope methods and other methods such as microfossils and geomagnetic reversals are discussed. The book is very well written, aimed at the layperson, with a good balance between the science itself and the personalities involved. There are several appendices including a not-too-detailed description of the science behind radioisotope dating.

As with any other good book on the history of science, we get a good insight into the ups and downs of the scientific process, starting from the initial hypothesis through the various attempts to substantiate it, and the struggles to perfect and calibrate the measuring tools. From any good hypothesis, more comes out than was expected. I found particularly interesting the way in which Clair Patterson discovered the contamination of the environment by lead from leaded gasoline while trying to reduce lead contamination in his laboratory. Apparently this research was intially funded by the oil companies, then cut off when it seemed to threaten their product. Eventually his work led to the banning of lead in gasoline. Interesting parallels with the current controversy over anthropogenic global warming.

I recommend this book to anyone who is interested in the topics of radioisotope dating, archaeology, geology, evolution, astronomy, and the scientific process.

We've all certainly read or heard of newspaper or magazine articles describing a new kind of fossil, maybe a dinosaur, and the article almost always includes a reference to the age of that fossil.

If you have ever wondered how scientists determine the ages of things then this is the book for you.

McDougall does a superb job of presenting and discussing the highly technical field of radiometric dating in a way that allows scientists and non-scientists alike to enjoy the ride. MacDougall hooked me in the first chapter...OK...imagine this, hikers are traversing a glacier and they come across what looks like a mummified(?) person with half of its body exposed to the air and the other half frozen into the glacier itself. The hikers don't know what to make of this situation. When the find is described and broadcast paleontologists descend on the site and discover an ancient human frozen into the ice, extremely well preserved, but now partially exposed to the elements. Questions soon arise: Who was this individual? How did s/he become frozen in the ice? When did s/he die? The stage is now set for MacDougall to explain how scientists determine the ages of things.

MacDougall does a masterful job of presenting scientifically complex ideas in clear, concise, and extremely readable prose. Not only that, but he pulls it off in a way that just about anyone can follow along and make sense of what there is to know about radiometric and other methods of determing the absolute ages of things.

I particularly enjoyed the historical context MacDougall provides when he introduces a new topic or method. For example, he starts by describing the discovery of radioactivity and progresses through early relatively inexact dating methods to the much more reliable and precise modern methods used today. And, since this book was publishd in 2008 he is able to include even cutting-edge methods.

The book is of particular interest to me since I teach a college-level course in the nature of science, and course topics include the origin and age of the universe, the origin and age of the earth, and the evolutionary origins of the human body. While I already had a general understanding of radiometric dating, this book opened my eyes to the simplicity and complexity of methods used in the past and today to the work it takes to determine the ages of things.

If you have ever wondered how scientists concluded that the earth is about 4.5 billion years old, or how they determine the ages of rocks, fossils, or pretty much anything else, then this book is for you.

MacDougall amazingly manages to address this topic in a comfortable 238 pp. of text, followed by some appendicies, and a glossary of terms, just in case you need to check something out.

This is a five-star read all the way! As soon as I finished I was sending out emails to colleagues telling them of my lucky find!

Thanks Doug! You've done a brilliant job!

Almost everyone has heard of radiocarbon dating, but it's applicable only for the last 50-thousand years or so. It's not common knowledge that much greater intervals of time can now be dated accurately. Doug Macdougall's Nature's Clocks offers a full and highly readable account of how scientists can date materials that formed many billions years ago. I found the book hard to put down.

Many students in earth science classes have been exposed to the geological Eras and Periods and these are properly and succinctly covered in the book. But that record is based on fossil evidence that extends only about 600 million years back, almost one-millionth of the earth's age. What happened before, and when?

Early consideration of the earth's age was based on biblical inferences and many people still subscribe to a faith based view. But objective treatments of earth's history began in the eighteenth century with James Hutton's Theory of the Earth, with Proofs and Illustrations. Hutton evaluated geological evidence but he and later geologists lacked objective measures of time. It was late nineteenth and early twentieth century advances in chemical and physical knowledge of heavy metals and radioactive decay that established the basis for modern techniques of determining ages of formation. Key players are identified in the development of these fantastically sensitive methods and the principles underlying each are explained. The relevance of dating materials to understanding the evolutionary and geological history of man is reviewed

There are no serious omissions in Macdougall's treatment; even the mathematical basis of measuring time via radioactive decay is simply and well explained although understanding the maths is unnecessary to enjoy and understand the book. Creationists take note: Nature's Clocks offers irrefutable evidence in support of stellar and biological evolution because the underlying phenomena can be measured and dated.