[.ca] The Birth of Time: How Astronomers Measure the Age of ... (ISBN 0300083467)

Surveys the mystery and explains how it was solved:
In the mid 1990s astronomers faced problems in dating the age of the Universe, with the Hubble providing information which seemed out of sync with previous observations and notions. By the end of the century scientists concurred on some remarkable facts which placed the age of the Universe at an age at least a billion years older than its oldest stars. This surveys the mystery and explains how it was solved.

Measuring the Universe:
Overall. I like the book. It had some short comings, and I get to those, but it did make approachable some of what astronomers do and how they do it. The book is basically a historical narrative of the science of astronomy and cosmology, and how they are continuously striving to answer some basic questions: How old is the Earth and consequently the Universe?; What is the nature of that Universe? In this regard, the book does very well. It introduces historical figures, what they did, how they did it, who they influenced, and a few interesting side trips to historical oddities that later proved prescient. There are historically significant people, and people significant only to the field in the book. The book however, is not so much about people as the questions asked (fundamentally remaining unchanged), the answers each generation uncovered (constantly changing with new insight and new precision of the fundamental technology), and the politics of the scientific community. The author makes approachable aspects of the theories of Einstein, Newton, Quantum Mechanics, the inner workings of stars and how this influenced astronomy. This is were the author is strongest. The weak areas are primarily in the paucity if figures, diagrams, and pictures to highlight and illustrate key techniques, theories, and technologies. What impressed me the most is how the science of astronomy and cosmology are built on estimates, built on assumptions, tied to just a few laws of nature or knowns. The answers the participants in the field devine from their work is constantly being refined as the estimates and assumptions are better understood or tossed out.

Measuring the Age and Size of the Universe:
Questions about the age of the universe are tightly coupled to understanding the size and structure of the universe. John Gribbin, a research astronomer as well as a popular writer, tells the story of how astronomers and physicists gradually recognized that the universe was both very large and very old. We all know today that the universe is immense, that the Milky Way is one of many galaxies, the age of the universe is measured in billions of years, and it began with a big bang. This fundamental understanding is actually quite new. In 1920 the scientific community was deeply divided over whether the Milky Way was essentially the entire universe or whether other large galaxies existed. The age of the universe was significantly underestimated. The Big Bang Theory was first considered seriously in the 1940s. The Birth of Time is a 200-page detailed look at how this remarkable story unfolded. Gribbin writes well and his explanations are quite lucid. We learn not only about major breakthroughs, but we also explore blind alleys and dead ends. It is an exciting, intriguing story, one that definitely warrants reading. Nonetheless, this book has one major drawback. Gribbin fails to use explanatory drawings or graphs. For example, he describes the Hertzsprung-Russell (H-R) diagram entirely in words. We laboriously read: So in a diagram (a kind of graph) where the brightness of each star (its absolute brightness, after allowing for how far away it is) is plotted against its colour, all hydrogen-burning stars lie along a single band in the diagram, a band which is called the main sequence, running roughly diagonally from top left to bottom right. Likewise, without any diagrams or graphs, or equations, Gribbin discusses parallax measurements, the redshift-distance relation, Hubble's Constant, gravitational lensing, spectral lines, and the Cepheid period-luminosity relation. (There were eight black and white full page astronomical photos that were indeed helpful.) I hope John Gribbin updates his work to include recent findings regarding dark matter and dark energy, and the now highly precise age (13.7 billion years) assigned to the universe. I reviewed the 2000 edition published by Universities Press.

Interesting, but lacking:
This book is an interesting history of the process of developing methods to determine the age of the stars and the universe. The author makes it very clear that there are assumpitons upon assumption, but that steady progress is being made and that different techniques are converging to common answers. Much emphasis is given to the importance of the Hubble Factor and why we still csn't call it a Hubble Constant. I found that, and the quest for refining the Hubble value very interesting. One of the keys to these estimates is Cepheid variable stars. More explanation of what these stars are, theories about them, and how they are used would be helpful. So would some charts and diagrams. Also how they are distinguished from the other types of variable stars thta are mentioned. I have read other explanations of Cepheid stars, for instance in StarDate magazine, and know that they can be explained well even in relatively non-technical terms. I would also have liked more stragihtforward explanation of how the Hubbble factor is used, not just that it is used.

Excellent Overview on the Astronomical Timescale:
As a geology instructor I have often taught students the age of the Earth and the age of the Universe. Although I have a thorough understanding of the methods by which the age of the Earth was determined, I really had no idea how astronomers dated the Universe. Thus, I read this book with great interest after I came across it in the library one day. Gribbon's book is written in a way that is accessible to the non-astronomer, but not so watered down as to make the story seem oversimplified. His explanation of the methodologies with which the Universe was dated is quite good and easy to follow. But the really interesting aspect of the book is the way he follows the stories about how the field developed and progressed. In fact, the competition and collaboration between the many notable scientists working in this field is perhaps as interesting as the science itself. Towards this end I am going to have students in one of my classes read an excerpt of this book so that they can see how collaboration and competition between scientists can at one time hold a field back and at another stimulate rapid advances in understanding. I highly recommend this book to anyone interested in the Earth Sciences, Astronomy, Physics, etc.