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a hefty tome called annals of the old testament ； that the earth had been1there will be no testing here； but if you are ever required to memorize them you might wish to remember johnwilfords helpful advice to think of the eras （precambrian； paleozoic； mesozoic； an（ cenozoic） as seasons in ayear and the periods （permian； triassic jurassic； etc。） as the months。
created at midday on october 23； 4004b。c。 ； an assertion that has amused historians andtextbook writers ever since。
2there is a persistent myth； incidentally—and one propounded in many serious books—thatussher’s views dominated scientific beliefs well into the nineteenth century； and that it waslyell who put everyone straight。 stephen jay gould； in time’s arrow； cites as a typicalexample this sentence from a popular book of the 1980s： “until lyell published his book；most thinking people accepted the idea that the earth was young。” in fact； no。 as martin j。 s。
rudwick puts it； “no geologist of any nationality whose work was taken seriously by othergeologists advocated a timescale confined within the limits of a literalistic exegesis ofgenesis。” even the reverend buckland； as pious a soul as the nineteenth century produced；noted that nowhere did the bible suggest that god made heaven and earth on the first day；but merely “in the beginning。” that beginning； he reasoned； may have lasted “millions uponmillions of years。” everyone agreed that the earth was ancient。 the question was simply howancient。
one of the better early attempts at dating the planet came from the ever…reliable edmondhalley； who in 1715 suggested that if you divided the total amount of salt in the world’s seasby the amount added each year； you would get the number of years that the oceans had beenin existence； which would give you a rough idea of earth’s age。 the logic was appealing； butunfortunately no one knew how much salt was in the sea or by how much it increased eachyear； which rendered the experiment impracticable。
the first attempt at measurement that could be called remotely scientific was made by thefrenchman georges…louis leclerc； te de buffon； in the 1770s。 it had long been knownthat the earth radiated appreciable amounts of heat—that was apparent to anyone who wentdown a coal mine—but there wasn’t any way of estimating the rate of dissipation。 buffon’sexperiment consisted of heating spheres until they glowed white hot and then estimating therate of heat loss by touching them （presumably very lightly at first） as they cooled。 from thishe guessed the earth’s age to be somewhere between 75；000 and 168；000 years old。 this wasof course a wild underestimate； but a radical notion nonetheless； and buffon found himselfthreatened with exmunication for expressing it。 a practical man； he apologized at oncefor his thoughtless heresy； then cheerfully repeated the assertions throughout his subsequentwritings。
by the middle of the nineteenth century most learned people thought the earth was at leasta few million years old； perhaps even some tens of millions of years old； but probably notmore than that。 so it came as a surprise when； in 1859 in on the origin of species ； charlesdarwin announced that the geological processes that created the weald； an area of southernengland stretching across kent； surrey； and sussex； had taken； by his calculations；306；662；400 years to plete。 the assertion was remarkable partly for being so arrestinglyspecific but even more for flying in the face of accepted wisdom about the age of the earth。
3itproved so contentious that darwin withdrew it from the third edition of the book。 the2although virtually all books find a space for him； there is a striking variability in the details associated withussher。 some books say he made his pronouncement in 1650； others in 1654； still others in 1664。 many cite thedate of earths reputed beginning as october 26。 at least one book of note spells his name 〃usher。〃 the matter isinterestingly surveyed in stephen jay goulds eight little piggies。
3darwin loved an exact number。 in a later work； he announced that the number of worms to be found in anaverage acre of english country soil was 53；767。
problem at its heart remained； however。 darwin and his geological friends needed the earth tobe old； but no one could figure out a way to make it so。
unfortunately for darwin； and for progress； the question came to the attention of the greatlord kelvin （who； though indubitably great； was then still just plain william thomson； hewouldn’t be elevated to the peerage until 1892； when he was sixty…eight years old and nearingthe end of his career； but i shall follow the convention here of using the name retroactively）。
kelvin was one of the most extraordinary figures of the nineteenth century—indeed of anycentury。 the german scientist hermann von helmholtz； no intellectual slouch himself； wrotethat kelvin had by far the greatest “intelligence and lucidity； and mobility of thought” of anyman he had ever met。 “i felt quite wooden beside him sometimes；” he added； a bit dejectedly。
the sentiment is understandable； for kelvin really was a kind of victorian superman。 hewas born in 1824 in belfast； the son of a professor of mathematics at the royal academicalinstitution who soon after transferred to glasgow。 there kelvin proved himself such aprodigy that he was admitted to glasgow university at the exceedingly tender age of ten。 bythe time he had reached his early twenties； he had studied at institutions in london and paris；graduated from cambridge （where he won the university’s top prizes for rowing andmathematics； and somehow found time to launch a musical society as well）； been elected afellow of peterhouse； and written （in french and english） a dozen papers in pure and appliedmathematics of such dazzling originality that he had to publish them anonymously for fear ofembarrassing his superiors。 at the age of twenty…two he returned to glasgow university totake up a professorship in natural philosophy； a position he would hold for the next fifty…threeyears。
in the course of a long career （he lived till 1907 and the age of eighty…three）； he wrote 661papers； accumulated 69 patents （from which he grew abundantly