Pharyngula

Bones, Rocks and Stars

How do we know how old things are? That’s a straightforward and very scientific question, and exactly the kind of thing students ought to ask; it’s also the kind of question that has been muddled up by lots of bad information (blame the creationists), and can be difficult for a teacher to answer. There are a great many dating methods, and you may need to be a specialist to understand many of them…and heck, I’m a biologist, not a geologist or physicist. I’ve sort of vaguely understood the principles of measuring isotope ratios, but try to pin me down on all the details and I’d have to scurry off and dig through a pile of books.

I understand it better now, though. I’ve been reading Bones, Rocks and Stars : The Science of When Things Happened(amzn/b&n/abe/pwll) by Chris Turney.

It’s a slim volume, written by a specialist specifically for the non-specialist, and it is highly focused on that one question: how do we date objects and events? I consider that a virtue. At the same time that Turney is exploring a subject in depth, he’s also able to keep the discussion general enough that anyone with an interest can read it. That’s also clearly his goal, to make his specialty approachable by the general public.

When I started this book, I was concerned that science wasn’t being effectively communicated. It seemed to me a real danger that society was enjoying the benefits of knowledge without understanding how it was gathered. I still feel this is a very real problem. You often hear folk bemoaning that science is ‘too hard’ or ‘too difficult’. This is a great pity. Science is terribly exciting and I hope that by writing this book, I’ve given a few insights into this exhilaration. Science has a tremendous amount to offer to improve the quality of life for all of us on this piece of rock we call home. The need is an urgent one.

Another pleasant surprise to this liberal-artsy reader is that the book isn’t all about physics. It’s organized in chronological order, sensibly enough, working backward through time and explaining how each progressively older problem is puzzled out. The first chapter is on calendar systems: when a historian has a date from a primary source that uses their calendar, how does she work out when it happened in our calendar, or by relative dating? Let me tell you, if you think science is hard, wait until you see all the special cases and dropped dates and finagled season-fitting and combinations of calendars that historians have to work over. It was a relief when he moved on to the simple clarity of mere geochemistry.

It’s not as if he abandons the wide-ranging approach in subsequent chapters, though. The penultimate chapter is on dating the age of the earth, and there we get a history lesson, discussing Ussher and Hutton and Lyell and Kelvin, before learning about radioactive decay and isotope series.

The final chapter is on creationism, and really, he doesn’t have to work too hard at that point. Everything else in the book has built up so well to documenting the evidence for an old earth that bringing out the young earth creationists is almost an example of comic relief. He neatly dismisses the YEC idea that the speed of light has been changing by pointing out that E=mc2: so “a small change in the speed of light can have a disproportionately large effect on the amount of energy produced from radioactive decay,” and that compressing 13.7 billion years into 6000 would mean so much energy would be released that the earth would be vaporized.

The audience for Bones, Rocks and Stars(amzn/b&n/abe/pwll) is, I think, anyone with an interest in the subject. You do not need a college degree to read the book; you don’t even need to have taken freshman chemistry. The focus is on context and concepts and comprehension, not the nit-picky details, and it is illustrated with concrete examples (When would King Arthur have lived? How old is the Shroud of Turin? When did the Ice Ages occur? How do we date the meteor strike that killed the dinosaurs?) Another key audience, I think, are high school teachers. If you’re teaching earth science or biology, and aren’t already thoroughly comfortable with the principles of geological dating, this book is an excellent survey of the topic. It will definitely help answer those pesky questions the creationists like to poke into kids’ brains in Sunday school, and even better, several of the chapters are outlines of good lesson plans in themselves.

What I like best about the book, though, is that it’s an example of a genre I’d like to see more often. It’s a scientist clearly and simply explaining what he does for a living, at a level that any literate person can understand, and explaining why it is important. That’s not an easy accomplishment.