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SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond. Lecture 15 31 March 2014 Science Center Lecture Hall A. Outline: … Finally Fossils. Filling in few facts
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SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond Lecture 15 31 March 2014 Science Center Lecture Hall A
Outline: … Finally Fossils Filling in few facts Finish “plate motions today: VLBI and SLR” Fossils: 1. Words on fossils and their formation 2. Ancient history (including Griffin story), Leonardo, Gesner, Cuvier, Anning, Mantell, Owen,…
Filling In • Holmes and Hess: very similar ideas, albeit with key differences, but different times and technologies (see reading assignment) • Wegener and “measured” rate of separation of Greenland from Europe of ≈ 10 m/yr: nearly 3 orders of magnitude too high • Why wouldn’t falsifier and his team realize that they’d eventually be caught? Why did Goddard require about year of my complaints before taking them seriously? 4. Why was “continental drift” replaced by “plate tectonics”?
Results From Radio Interferometry Successful measurement of current drift rate achieved in 1985 with Very Long Baseline Interferometry (VLBI) across Atlantic (last lecture). Rate consistent with long-term average; subsequent work also consistent Possibility of using VLBI technique with satellites conceived c. 1970. GPS allowed realization of potential, fromearly 1980s on. Now world-wide cottage industry; “long-period” seismometer. Scientific results: measurement of intra-plate as well as inter-plate motions; variations in rotation of earth, motion of its pole; precession and nutations; and deductions on shape of core-mantle boundary. Still no useful earthquake prediction capability
Results From SLR Superb spatial resolution for earth’s gravity field and its time variation. (Why time variation?) Location of earth’s center of mass with respect to its surface Motion of earth’s pole of rotation (wrt surface)
Fascinating Faces of Fossils What is a fossil? - Ancient and modern definitions How are fossils produced? Greco-Roman views of fossils Renaissance developments Modern discoveriesand understanding
What Is AFossil? Origin of word: object “dug up” Ancient: Anything “interesting”qualifies Modern: Anything once connected with organic matter
Rate Of Fossil Production? No one knows. But clear that fossils rare compared to number of organisms that lived. (1 in million or less, overall? Much less, counting insects, etc.) Conditions have to be just right. Also fossil formation favors organisms with hard shells or skeletons; soft organisms decay too easily
How Are Fossils Produced? (Count the Ways) Taphonomy: - Permineralization - Molds and Casts - Preserved in amber - Replacement and re-crystallization - Bioimmuration . . .
Permineralization Minerals deposited (seep) within cells of organisms - Minerals could be, e.g., silicates, calcium and magnesium carbonates, or iron sulfides - Preserves cell structure; helps prevent tissue compaction - First step to petrification (=cellulose cell walls also replaced by minerals)
Trilobite: Apparent Facts Lasted: from about 550 to 250 million years ago (extinction event) Sizes: from about 1 mm to 0.7 m, ratio of 700:1 Needed to molt as grew: in principle, more than one fossil from given trilobite Lifetimes of individuals: ?? First organisms known to have vision (360 deg!) Some could roll into ball, presumably for protection
Molds And Casts Organism buried in sediments Original dissolved or otherwise destroyed, leaving hole (“mold”) Filled with other minerals, it is then cast; can exist by self Note 1: Not like cast on, say, arm Note 2: There are internal and external molds, as well
Amber Fossilized tree resin (complicated chemical production) Unique preservational mode Oldest amber fossil: several 100 million years Preserves insects, spiders + webs, flowers, fruit, bacteria,… No evidence DNA preserved
Views of Ancients Awareness of fossils (Aristotle’s views) Locations and explanations Mixture of history and mythology (illustrated by the [partial] story of the Griffin) Paucity of surviving documents (no mention of large bones)
Earliest Fossil Finds And Related(?) Myths: The Griffin - Scythian nomads and guarding of gold - Griffin legend and its spread (mentioned in Aeschylus’, “Prometheus Bound,” c. 500 BCE) - Possible connection with protoceratops - Irresistible aside: protoceratops- velociraptor conflict
Fathoming Fossils With Science Leonardo leads (but who follows?) Unusual approach to everything, including writing and science The puzzle of marine fossils near mountaintops Others blame it on THE flood; Leonardo’s acute analysis (next reading assignment)
Major Innovations by Conrad Gesner (1516-1565) For fossil research: - Illustrations to supplement words - Established collections (think museums) - Established scholarly committees (cooperation by correspondence)
“Fallow” Period Before Sustained Interest After Leonardo and Conrad Gesner and his cabinet Before Georges Cuvier and his mammoth
Some Contributions to Science By Georges Cuvier (1769-1832) - Established extinction - Proponent of catastrophism - Helped establish field of stratigraphy - Coined “Paleontology” - Identified (in print) and named “Pterodactyl” - “No larger animals remained undiscovered” (1821)
Today comparative anatomy has reached such a point of perfection that, after inspecting a single bone, one can often determine the class, and sometimes even the genus of the animal to which it belonged, above all if that bone belonged to the head or the limbs. ... This is because the number, direction, and shape of the bones that compose each part of an animal's body are always in a necessary relation to all the other parts, in such a way that - up to a point - one can infer the whole from any one of them and vice versa. Georges Cuvier 1798
The Era Of Large Fossils Historical approach: early to mid 19th century Cast of characters: - Mary Anning. Stratigraphic source of large bones she discovered - Gideon Mantell. Found iguanodon bone - Richard Owen. Named dinosaurs - William Foulke and Joseph Leidy. Found first nearly complete dinosaur
Mary Anning (1799-1847) The extraordinary thing in this young woman is that she has made herself so thoroughly acquainted with the science that the moment she finds any bones she knows to what tribe they belong. She fixes the bones on a frame with cement and then makes drawings and has them engraved... It is certainly a wonderful instance of divine favour—that this poor, ignorant girl should be so blessed, for by reading and application she has arrived to that degree of knowledge as to be in the habit of writing and talking with professors and other clever men on the subject, and they all acknowledge that she understands more of the science than anyone else in this kingdom. Lady Harriet Silvester (1824)
