| Firmly entrenched and supported by the church, | | | | rate, it would be possible to work backward to a time |
| Ussher's date seemed impregnable. However, some | | | | when the seas contained no salt at all, which would |
| skeptics put forward their own versions. A French | | | | then give the age of the Earth. In 1715, this was a |
| Calvinist and lawyer, La Peyrere in 1641 postulated that | | | | fantastic idea, but no one, least of all Edmond Halley, |
| there had been people on Earth before Adam. This | | | | knew how to measure increases in salinity year on |
| was heresy and of course was banned by Cardinal | | | | year, and he concluded that the observations would |
| Richelieu, the prime minister of France. Essentially a | | | | need to be made a century apart to be meaningful. |
| pragmatic and fair man, he however realised what | | | | However Methuselah, in spite of his famed longevity, |
| effect La Peyrereses manuscript might have in | | | | was no longer alive, so this was impossibility. |
| France. La Peyrere kept this freedom, but he did not | | | | Georges Louis Leclerc Buffon was the next to |
| desist with his theories, eventually in 1655 invoking the | | | | estimate the age of the Earth. He was well connected |
| wrath of the Catholic Church. He was arrested, | | | | with the French court and had the ear of several of |
| interred and forced to recant his heretical views - in | | | | the crowned heads of Europe. Clever, hard working, |
| short he got off lightly. Enter another player on this | | | | and somewhat eccentric, he proposed the idea that |
| grand stage - a Jesuit missionary, Farther Martino | | | | the Earth's age could be estimated by the rate at |
| Martini, who was carrying out missionary work in China. | | | | which it cooled. |
| On telling the Chinese that mankind had been | | | | He heated up metal spheres and then estimated the |
| destroyed by God in a great deluge, they greeted his | | | | rate of heat loss as they cooled, and then |
| pronouncements with great hilarity and disbelief. Their | | | | extrapolated this to the larger Earth, settling on the age |
| own history stretched well beyond the so-called date | | | | of 75 000 to 168 000 years. This was a quantum leap |
| of the Flood, and they had records to prove it. A | | | | from the 6000 year old theory and he nearly got |
| reversal of roles took place, with Martini realising that | | | | excommunicated for his troubles. Being a politically |
| the ancient Chinese chronology posed a serious | | | | astute animal, he recanted his heresies but then |
| challenge to the authority of the bible. In 1654 he | | | | proceeded to repeat his assertions for the rest of his |
| returned to Europe, where he published an account of | | | | days. |
| Chinese history, receiving of course the usual disbelief | | | | Charles Darwin, apparently unhappy with creating |
| and hostility which marked all other controversial ideas | | | | controversy, but brave enough to do so anyway, |
| perpetuated at the time. However arrest and | | | | suggested that the Earth was 300 million years old. |
| persecution was out of the question as Martini had | | | | This date proved so contentious that he actually |
| returned to China to further his missionary work. | | | | withdrew it from his Origin of the Species. The great |
| Europe continued her dyed-in-the-wool approach, but | | | | Lord Kelvin, who towered over Victorian science like a |
| slowly thinking was evolving, with crucial intellectual shift | | | | colossus, took Darwin to task for some of his |
| away from biblical textual authority towards an enquiry | | | | assertions, and declared that the Earth cold be no |
| based on scientific principles. Throughout Europe the | | | | older than 24 million years, which were downward |
| cry was the same: rocks, not books were believed to | | | | revisions of an original figure of 400 million. However, in |
| hold the secrets of the past. And indeed they did, and | | | | spite of Kelvin's phenomenal intellect, he was not |
| still do, and it was left to the natural philosophers to | | | | aware of the invisible heat source deep with the Earth |
| prove the age of the world. | | | | - radioactivity - which drives the engine of our planet. |
| One of the more interesting notions of the 17th | | | | Radioactivity is a concept to which we have become |
| Century was that the Earth had been created fully | | | | accustomed to thanks to the popular press, nuclear |
| formed; flat, beautiful, unblemished, with no disease, | | | | power and its use in the medical field. But is Kelvin's |
| famine, mountains or deserts to blemish her perfect | | | | day it was still unknown, and it was thanks to the |
| face. A golden age had existed before the Flood, and | | | | pioneering work by Marie and Pierre Curie that |
| age when all God's blessings were poured out onto | | | | radioactive material was first recognised and isolated. |
| the world - in short a perfect God had created a | | | | Earnest Rutherford then provided the world with an |
| perfect world. But now things were in decline - the | | | | explanation of how it all worked, and of the energies |
| Earth had become old and wrinkled, volcanoes and | | | | released in the process - which then provided a |
| deserts were carbuncles and scars on the face of the | | | | mechanism for keeping the interior of the Earth at |
| Earth. An old prophecy that the world would last only | | | | elevated temperatures. Other great names of nuclear |
| 6000 years was being confirmed by nature. The | | | | physics come from this time - Bohr, Heisenberg, |
| thinking was that the Earth had run most of its days, | | | | Thompson, Chadwick and of course Einstein. The |
| and doomsday was not far off, perhaps only 350 | | | | properties of the atom and the elements became |
| years in the future (taking of course the date of 4004 | | | | increasingly understood as well as the chemistry and |
| BC as the day of creation). | | | | isotopes of radioactive elements. |
| However this idea of an ageing Earth brought the | | | | This understanding of radioactive half lives became |
| notion of a world in flux and a constant state of | | | | fundamental to the dating of rocks, Professor Arthur |
| change to the fore, and it was Rene Descartes who | | | | Holmes of Durham University took up the cudgels and |
| lead the break with the literal interpretation of the bible. | | | | pioneered the methods which are used to this day. |
| Reason was the reason de etre. Paris, 1625, and our | | | | The technique was based on Rutherford's 1904 work, |
| clever and sociable Descartes had become the | | | | when he discovered that atoms decay from one |
| leading light of Parisian intellectual life - a time when | | | | element into another at a rate predictable enough to |
| libertine free thinkers were making their mark. Caution | | | | allow them to be used as clocks. |
| was always necessary and a weather eye was kept | | | | Holmes measured the rate of decay of uranium to |
| open for gathering storm clouds in the direction or | | | | lead, and used this to calculate the age of the Earth. In |
| Rome. One Giulio Vanini, a 'heretic' doctor, had had his | | | | spite of a lack of funds and sophisticated equipment, |
| tongue cut out before being strangled and burned six | | | | he announced in 1946 that the Earth was at least 3 |
| years before for voicing some anti religious views. | | | | billion years old. His methods met with praise, but his |
| Inevitably the storm broke and Descartes moved to | | | | date was not. But he was far closer to the mark than |
| Holland, a country which has always had a tradition of | | | | Kelvin had been. |
| tolerance and liberalism which endures to this day. He | | | | Building on Holmes' pioneering work, Clair Patterson of |
| began his philosophical treatise, The World, which was | | | | the University of Chicago took up the challenge. The |
| to be a completer revision of philosophy which he | | | | problem with dating the Earth is that one needs rocks |
| eventually published in 1641. | | | | almost that old, and these are rare thanks to the |
| However it was a watered-down version of his | | | | ongoing cycling of crust due to plate tectonics. In |
| original manuscript as it was a bad time for liberal | | | | addition one needs uranium-bearing crystals within |
| thinkers. Galileo had recently been arrested and forced | | | | these rocks. Patterson made the assumption that if all |
| to recant his heretical views that the Earth went | | | | the lead on Earth came from radioactive decay, then it |
| around the Sun. Descartes' view of the world was | | | | would be easy to find the age of the Earth. The more |
| essentially that a few simple laws governed the | | | | lead a rock contained, the older it had to be. In reality all |
| universe, and these laws were what created the | | | | the lead on Earth did not come from uranium and it |
| complex world around us. The world had the same | | | | was impossible to separate out the 'primordial' lead - |
| relationship to God as a clock had to the clock maker | | | | that which had been around from the creation of the |
| - once it had been carefully constructed and set in | | | | Earth, from that derived from radioactive decay. To |
| motion, there was little more involvement from the | | | | sidestep this thorny issue, another brilliant assumption |
| creator. His ultimate achievement was to remove God | | | | was made, that meteorites were left over building |
| from the day to day running of the world. Until then the | | | | material dating back to the early days of the solar |
| belief was that God was intimately involved in the day | | | | system, and thus their lead content would be the same |
| to day, minute to minute running of the world. God may | | | | as that of the early Earth. Perhaps more importantly |
| have created the world, but it was then governed by | | | | they contained no uranium to upset the clock. None of |
| the laws of nature. | | | | the lead in meteorites then would have come from |
| Newton then swept away Descartes' imprecise | | | | radioactive decay. Harrison Brown, Patterson's |
| theories with his Principia - the laws governing the | | | | doctoral supervisor said this to him: |
| motions of the heavenly bodies were now defined in | | | | "Pat, you just go in and get an iron meteorite - I'll get it |
| minute detail. However his seems to have wasted his | | | | for you. We'll get the lead out of the iron meteorite. |
| intellect and the latter years of his life trying to tie the | | | | You measure its isotopic composition and you stick it |
| history of ancient kingdoms and biblical chronology into | | | | into the equation. And you'll be famous, because you |
| the record of astronomical events - eclipses and the | | | | have will have measured the age of the Earth." |
| arrival of comets - but with extremely limited success. | | | | It took Patterson 7 years to build a completely lead |
| His friend Edmond Halley then came up with the | | | | free laboratory and to obtain a result, which dated the |
| theory that the age of the Earth could be estimated | | | | Earth at 4550 million years. After three hundred years |
| by the amount of salt in the sea. By measuring the | | | | we had at last a date for the beginning of the World. |
| rate of increase of the sea's salinity, and assuming that | | | | And that figure still stands to this day. |
| salt had been washed into the oceans at a constant | | | | |