The Abyss of Time: Unraveling the Mystery of the Earth's Age
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The Abyss of Time: Unraveling the Mystery of the Earth's Age
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Product Details
| ISBN-13: | 9780486151168 |
|---|---|
| Publisher: | Dover Publications |
| Publication date: | 07/31/2012 |
| Series: | Dover Earth Science |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 256 |
| File size: | 5 MB |
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The Abyss of Time
By Claude C. Albritton Jr.
Dover Publications, Inc.
Copyright © 1980 Freeman, Cooper and CompanyAll rights reserved.
ISBN: 978-0-486-15116-8
CHAPTER 1
Introduction
The figures now considered by scientists as providing reasonable estimates of the earth's age are more than seven hundred thousand times greater than those in vogue three centuries ago. This expansion has not been upward on a uniform slope. During the seventeenth century the age of the earth was reckoned in the thousands of years. Estimates in the millions and even thousands of millions followed in the eighteenth century. During the late nineteenth century there was a general shrinkage to limits that fell as low as a few tens of millions. Now we think in terms of thousands of millions. These fluctuations have not been capricious, but have been prompted by increase in knowledge concerning the nature of matter in general and of that particular matter available for inspection in the outermost parts of the solid earth.
Some of the earlier estimates were based upon interpretations of Scripture. During the fourth century of the Christian era, Eusebius of Caesarea devised a chronicle based on Jewish historical traditions reaching back in time to the birth of Abraham. Eusebius Hieronymus (Saint Jerome) extended the chronicle back to Adam. Efforts to derive a history of the earth and its inhabitants from Biblical sources culminated in the seventeenth century with the work of James Ussher, Irish scholar and theologian. Ussher's chronology placed the date of creation in the year 4004 B.C., and this figure has since been imprinted in many editions of the Bible.
The scientific revolution of the seventeenth century did not produce developments in geology so spectacular as those in mathematics, astronomy, physics, and chemistry. Nevertheless, two ideas which would later have great influence on historical geology had emerged before 1700. Fossils were coming to be accepted as remains of organisms rather than sports of nature. And the layered rocks containing these fossils were recognized as having accumulated layer by layer. Thus the order in which the layers are stacked is chronologic. The principle of superposition of strata, which embodies this concept, states that in a sequence of strata, as originally laid down on the surface of the solid earth, any stratum is younger than the one it rests upon and is older than the one that rests upon it.
The first of two time-explosions came during the 1700's. Estimates of the earth's age based on experiments with earth models yielded figures up to three million years. Speculations based upon a supposed secular shrinking of the world ocean led to a figure of two thousand million years. A leading scientist of the century, on viewing the evidence for repeated elevation and wearing down of the continents, concluded that geological time must be inconceivably long—virtually infinite in duration—in order to accommodate events of such magnitude.
Studies in France and England conducted between 1779 and 1815 established that within thick sequences of fossiliferous strata different kinds of fossils succeed one another in a definite order. This principle of faunal succession, combined with the principle of superposition, made possible the classification and chronologic ordering of fossiliferous rocks exposed over continental Europe and the British Isles. Individual strata were grouped into formations, and formations were combined into higher categories leading up to the geologic systems that we recognize today. The laborious task of classifying and identifying the chronologic order in which the systems are arrayed was essentially accomplished by 1845. At that time, however, the chronicle provided by the systems was only relative. One could say that a given system is younger than the one it overlies and older than the system next above, but not by how many years.
Until after the mid-nineteenth century, geologists were prone to claim almost any amount of time needed to account for the myriad events recorded in the rocks. Assuming an indefinitely large allowance of time, Darwin constructed his theory of organic evolution on the basis of the slow-working process of natural selection.
Soon after Darwin's Origin of Species appeared in 1859, however, there was a sharp recession in the amount of time thought to be allowable for the history of the earth and the evolution of life. On the assumption that the earth is an inert mass that was originally molten, Lord Kelvin calculated the time that would be required for cooling to its present condition. The figures he proposed varied throughout the years when he addressed this problem; but by the end of the century he was convinced that the earth could not have supported life for more than 20 to 25 million years.
Geologists reacted to Kelvin's abbreviated time scale by devising numerical scales of their own. One method of arriving at numbers was to divide the maximum thickness of the geological column by the average yearly rate at which sediments are accumulating at present. Another "hourglass" approach used the ratio between the total amount of sodium in sea water and the amounts of that element annually added at present. In either instance one could arrive at nearly any figure he pleased, by juggling values of the several variables within whatever seemed permissible limits. Not surprisingly, many of the quotients fell out around a hundred million, an age Kelvin had suggested during his more generous years.
A second time-explosion was triggered in 1896 by the discovery of radioactivity. The facts that naturally radioactive substances are widely disseminated in the outer parts of the earth and that radioactive decay entails release of heat put an end to Kelvin's time scale. Beyond that, ratios between parent and end products in certain lineages among radioactive series yield ages in years for the substances that contain them. Radiometric dating is mainly responsible for the calibration of the relative scale of time worked out by the geologists. Results to date indicate that the earth is more than 3,700 million years old.
This bare sketch of the ups and downs of geologic time now completed, we can turn to the whys and the wherefores and the interesting persons responsible for these changes in our perspective on time.
CHAPTER 2Malta's Cradle
Above the plains of Italy, where flocks of birds are flying today, fishes were once moving in large shoals.
LEONARDO DA VINCI
In the autumn of 1666 some men fishing in the Ligurian Sea caught a great white shark and dragged it ashore near Leghorn. The landing of a white shark was a notable event then, as it is today, for of all fish this is considered the most dangerous to man. Word of the catch spread to the Medici Court in Florence. By order of the Grand Duke Ferdinand II the shark's head was cut off and brought for examination to one Nils Stensen, M.D., a twenty-nine-year-old Dane who had latinized his name to Nicolaus Stenonis (now usually anglicized to Steno). The chain of events which led to the conjunction of an extraordinary fish with an extraordinary prince and an extraordinary doctor of medicine resulted in the publication of what has been called the first geological treatise, and in the elucidation of three basic principles of historical geology. A brief introduction to each of the three characters in this strange cast is thus in order.
Carcharodon carcharias, as the great white shark is known to zoologists, is one of nine man-eaters among the more than 250 kinds of sharks living today. Adult specimens average around 18 feet long, although individuals estimated to be twice this length have been sighted. The behavior of this species in the presence of men or boats is unpredictable: authenticated accounts of the fish's fleeing in apparent fright from divers contrast strangely with equally reliable records of its damage to fishing boats by repeated ramming and of occasional savage and fatal attacks upon swimmers. Though not abundant today, the white shark is wide-ranging throughout the temperate seas of both hemispheres. Judging by the gape of the specimen examined by Steno, the entire animal was 14 or more feet long, and probably weighed about a ton (1).
Ferdinand II was 18 years old when he took charge of the government of Tuscany in 1628. The wealth and political influence of the Medici family, already in decline before the death of his father in 1620, continued on the downgrade through the half century of his rule. During the years of his minority, affairs of state were managed, or rather mismanaged, by his mother and grandmother acting as co-regents according to the will of Cosimo II (1590-1620). In defiance of this will, however, the treasury of the house was squandered and the regents adopted a submissive and subservient attitude toward the Holy See. Despite the ecclesiastical influence prevailing in the court, however, Ferdinand's mother, the Grand Duchess Maria Maddalena, sent each of her sons to study physics with Galileo (2).
Ferdinand is remembered more for his generous disposition, his love of peace, and his cultivation of the arts and sciences than for his administrative ability. Among other accomplishments he sponsored the work of the Accademia del Cimento, founded in 1657 by his brother Leopold. Over the period of a decade, members of this "Academy of Experiment" developed new and reliable instruments for the measurement of the temperature and humidity of the atmosphere. The Grand Duke himself is credited with the invention of the condensation hygrometer, a device for measuring the humidity of the air depending on the formation of dew on surfaces artificially cooled. He was also the first to overcome the sensitivity of tubular thermometers to changes in barometric pressures by hermetically sealing the upper ends of tubes partly filled with liquids.
This active interest in the advancement of science on the part of Ferdinand made possible Steno's entry into the scientific circles of Florence. In 1667 Steno was given a monthly pension and was assigned rooms in the Palazzo Vecchio (3).
Steno was born in Copenhagen in 1638. His father, Sten Pedersen, came from a family of preachers but chose goldsmithery as his trade. Pedersen's work with precious metals and stones must have been good, because his shop was called upon to supply the courts of the Danish kings Christian IV and Frederick III.
After training in a Latin school, Steno was admitted to the University of Copenhagen in 1656. There he studied with Thomas Bartholin (1616–1680), professor of anatomy, whose fame rests mainly on his pioneer studies of the human lymphatic system. After some three years of study Steno went on an educational journey to Holland. Early in his residence at Amsterdam he discovered the excretory duct of the parotid gland to the mouth. Textbooks of anatomy still refer to this vessel as "Steno's duct."
As a student at the University of Amsterdam Steno published and defended a scholarly disputation on thermal springs, their mineral content and sources of heat (4). Thus his first publication was on a geological subject, though his primary interest in spring waters probably lay in their real and supposed medicinal values. In any case he continued anatomical and medical studies at the University of Leiden, where he conducted research on glands over a period of two years.
Steno did not tarry at Leiden to receive his M.D. degree, which was awarded in absentia while he was conducting studies of muscles and embryos in Paris. There he had the good fortune to become a member of a circle of research-minded savants led by Melchisédech Thévenot (c. 1620–1692). One of the founders of the French Academy of Science, Thévenot was a physician by training but was also a master of Oriental languages, an inventor of surveying instruments, a bibliographer, and after 1684 Librarian of the Royal Library. In 1665 Steno prepared for the Thévenot group a lecture on the anatomy of the brain, a work that has since become famous and is still in print (5).
In mid-September of 1665 Steno left Paris and set out for Italy. What led him to undertake this arduous journey of more than 1,500 miles is not known. Some have suggested that he wished to become acquainted with Galileo's group of students in Florence. However that may be, in late March or early April of the following year he arrived at Pisa, the winter residence of the Medici Court. There his attachment to Ferdinand II began.
When Steno received the shark's head, he was preparing for publication a lengthy report on the geometry of muscles. In 1667 his account of the shark appeared as a supplement to this longer work under the title Canis carchariae dissectum caput ("The head of a shark dissected") (6). Here we are reminded that the significance of a scientific document is not to be gauged by its length, for while Steno's geometry of muscles is remembered mainly as an egregious example of how mathematics can be misapplied to biological problems, the supplement stands as a geological classic. Moreover, that part which is so highly esteemed is not the description of the specimen at hand but a digression into the origin and significance of certain curious objects known from antiquity as glossopetrae or "tonguestones."
Glossopetrae are flattish objects, in side view resembling equilateral triangles, with heights ranging to four inches or more. The thickened bases taper to pointed or narrowly rounded ends along sides with serrate edges. Faces are commonly enameled and shiny, and their colors range from light gray to almost black. Viewed from above, the concave side bears a gruesome resemblance to a tongue that has been turned to stone. Tonguestones are found embedded in rock or lying on the surfaces of rocks that contain them. The overall appearance of these objects is sufficiently striking to attract the attention of anyone interested in natural curiosities.
Though glossopetrae have been found in various parts of the world, those from the Maltese Islands have played the largest role in folklore and in the science of paleontology (7). By the early part of the seventeenth century specimens from Malta were widely scattered over Europe in private collections and museums. Steno had probably seen the Maltese tonguestones that were in collections at the University of Copenhagen when he was there as a student. His professor, Bartholin, had visited Malta but could make no final decision as to the origin of these curiosities.
An early, perhaps the earliest, reference to tonguestones is found in the last book of Pliny's Natural History. In the following passage Pliny seems willing to grant that these stones have fallen from heaven, but questions their power to excite sexual desires or to stay flatulence. The quotation is from Philemon Holland's text of 1601, earliest translation of the Natural History into English.
Glossi petra resembleth a mans tongue, and groweth not upon the ground, but in the eclipse of the moone falleth from heaven, and is thought by the magicians to be verie necessarie for pandors and those that court faire women: but we have no reason to believe it considering what vaine promises they have made otherwise of it; for they beare us in hand, that it doth appease winds. (8)
A distinctively Maltese hypothesis for the origin of tonguestones relates them to an unscheduled visit of Paul the Apostle to the island in A.D. 59. Shipwrecked near the bay that now bears his name, Paul was bitten by a viper. To the amazement of the natives, he suffered no ill effect (9). Paul's curse upon all the snakes of the islands deprived them of their venom and turned their teeth into the tonguestones. Another version maintains that replicas of the tongues and not the teeth of the snakes grew in the earth following the miracle worked by the Apostle. Hence the names Maltese tonguestones or St. Paul's tongues. Certain country people of Malta still believe that the "Ilsien San Pawl" has the power to cure human ailments. (10)
According to a third tradition, maintained until late in the seventeenth century, tonguestones are simply minerals that have grown in the earth. Their resemblance to tongues or teeth is coincidental or the result of natural or supernatural forces acting in a frolicsome manner.
Lusus naturae ("sport of nature") was a catch-all term commonly applied to fossils during the seventeenth century and before. In October of 1663, James Long, a member of the Royal Society of London and a writer on agriculture, wrote a letter to Henry Oldenburg, Secretary of the Society, telling about finding some objects resembling the shells of snails ("screwstones") and clams embedded in sandstone.
(Continues...)
Excerpted from The Abyss of Time by Claude C. Albritton Jr.. Copyright © 1980 Freeman, Cooper and Company. Excerpted by permission of Dover Publications, Inc..
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Table of Contents
To the Reader1. Introduction
2. Malta's Cradle
3. Solids within Solids
4. Mr. Hook(e)
5. A Sacred Theory of the Earth
6. Telliamed's Story
7. The Epochs of Nature
8. View from the Brink
9. Father William
10. The Four-dimensional Jigsaw Puzzle
11. A Question of Tempo
12. A Plenitude of Events
13. The Great Tree of Life
14. Kelvin
15. A Numbers Game
16. Radiometric Dating
17. World Enough and Time
Notes
References
Index of Names
Subject Index