The age of the Earth – how real science happens

If you want to teach about biology, or about the Bible, at Patrick Henry College for the evangelically home-schooled in Virginia, you will have to agree with the College’s view that “that God’s creative work, as described in Genesis 1:1-31, was completed in six twenty-four hour days.” Alternative views are to be presented, but should, “in the end, teach creation as both biblically true and as the best fit to observed data.”

Faculty teaching such courses might want to shield their eyes from the new Scientific American Classic, Determining the Age of the Earth, to which I wrote the introduction, for fear of having to change their minds and lose their jobs. For there they would find copies of articles, from 1857 to 1989, explaining in great detail just how, and after what exhaustive scrutiny, the scientific community was driven, much against its will, to conclude that “the best fit to observe data” requires a time of over 4.5 billion years.

Six days, of course, had long since ceased to be taken seriously as an estimate. The Scientific American account begins with Kelvin using arguments based on the then-new science of thermodynamics to challenge the geologists’ view that the earth was indefinitely old, and describes how he lowered his estimate from up to 100 million years to an upper limit of around 20 million. Meantime the geologists were developing what are sometimes called “hourglass” methods, based on observation of the Earth as it now is, and estimates of the rates of the processes that had brought it there. For instance, they  compared the total amount of salt in the oceans with the amount carried down in rivers annually. They added up the known thicknesses of sediments, and divided that by an estimated rate of deposition. This led them to estimates of around 100 million, enough (perhaps) for Darwinian evolution, but still longer than Kelvin was by the end willing to grant them.

When Rutherford’s group, followed in short order by Strutt, Arthur Holmes, and Bertram Boltwood, introduced radiometric dating, the geological community was initially sceptical. And with good reason. They were told that their careful estimates were wrong by a factor of five, then 10, and 20 or more. All this on the basis of a very poorly understood phenomenon. Remember that there was as yet no knowledge of the existence and nature of isotopes, the fact that there are three separate major decay sequences, or ways of distinguishing radiogenic from non-radiogenic lead. It was not until 1926, in fact, two decades after Rutherford’s initial work, that the method was generally accepted. And with our present knowledge, we can easily identify the flaws in the earlier reasoning, such as the inability to include the energy generated by nuclear processes, or the recycling of sediments back into the mantle. [Added edit: And, much more importantly, the role of convection in increasing the amount of heat to be disposed of; see here]

I had already written about this subject, mainly from the point of view of the conflict between Kelvin and the geologists. Nonetheless, I found it both enjoyable and instructive to retrace the thoughts of some of the scientists I had already met, and others whose names were new to me, in their own words and from the perspective of their own time. This was, for me, no mere antiquarian exercise, but an opportunity to experience for myself this wonderful story of discovery, not just from the point of view of the eventual winners, but as a journey over difficult terrain, where even concepts that we now recognize as misguided functioned, in their time, as signposts.

So what should we say about an institution of higher learning like PatrickHenryCollege? I would have preferred to say nothing at all, if it were not for the fact that it has an influence far beyond its numbers, that Professor John Lennox, whom I have discussed earlier, is speaking there next week, and that its 240-strong student body had by 2004 supplied seven out of the 100 interns in George W Bush’s White House, and support staff for 22 other politicians.


About Paul Braterman

Science writer, former chemistry professor; committee member British Centre for Science Education; board member and science adviser Scottish Secular Society; former member editorial board, Origins of Life, and associate, NASA Astrobiology Insitute; first popsci book, From Stars to Stalagmites 2012

Posted on April 4, 2013, in Creationism, Education, Politics, Religion and tagged , , , , , , , , , , , , . Bookmark the permalink. Leave a comment.

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