Various specimens of Tyrannosaurus rex with a human for scale. Size comparison of selected giant theropod dinosaurs, with Tyrannosaurus in purple. Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, FMNH PR ” Sue ” , measured The forelimbs were long thought to bear only two digits, but there is an unpublished report of a third, vestigial digit in one specimen. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.
How do scientists determine the age of dinosaur bones?
Mineralogy As a discipline, mineralogy has had close historical ties with geology. Minerals as basic constituents of rocks and ore deposits are obviously an integral aspect of geology. The problems and techniques of mineralogy, however, are distinct in many respects from those of the rest of geology, with the result that mineralogy has grown to be a large, complex discipline in itself.
Nepheline greasy light gray , sodalite blue , cancrinite yellow , feldspar white , and ferromagnesian minerals black in an alkalic syenite from Litchfield, Maine, U. About 3, distinct mineral species are recognized, but relatively few are important in the kinds of rocks that are abundant in the outer part of the Earth.
So we know that light acts like a wave.
How accurate are carbon-dating methods? All methods of radioactive dating rely on three assumptions that may not necessarily be true: Rate of Decay It is assumed that the rate of decay has remained constant over time. This assumption is backed by numerous scientific studies and is relatively sound. However, conditions may have been different in the past and could have influenced the rate of decay or formation of radioactive elements. Evolutionists assume that the rate of cosmic bombardment of the atmosphere has always remained constant and that the rate of decay has remained constant.
First unearthed in western Australia in and described in , these microfossils are so tiny that eight of them lined up one after another would span the width of a human hair. The researchers who discovered the fossils initially identified them as biological, but other scientists argued that it was impossible to say for sure, proposing that the so-called “fossils” were more likely odd-looking minerals.
However, when the authors of the new study used a novel method to inspect the delicate fossils on a molecular level, they detected certain carbon signatures indicating that the fossils were organic in origin after all.
Sorry for the delay.
Updated 8 January c Introduction In a related article on geologic ages Ages , we presented a chart with the various geologic eras and their ages. In a separate article Radiometric dating , we sketched in some technical detail how these dates are calculated using radiometric dating techniques. As we pointed out in these two articles, radiometric dates are based on known rates of radioactivity, a phenomenon that is rooted in fundamental laws of physics and follows simple mathematical formulas.
Dating schemes based on rates of radioactivity have been refined and scrutinized for several decades. The latest high-tech equipment permits reliable results to be obtained even with microscopic samples. Radiometric dating is self-checking, because the data after certain preliminary calculations are made are fitted to a straight line an “isochron” by means of standard linear regression methods of statistics. The slope of the line determines the date, and the closeness of fit is a measure of the statistical reliability of the resulting date.
Technical details on how these dates are calculated are given in Radiometric dating.
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This is what archaeologists use to determine the age of human-made artifacts. But carbon dating won’t work on dinosaur bones. The half-life of carbon is only 5, years, so carbon dating is only effective on samples that are less than 50, years old. Dinosaur bones, on the other hand, are millions of years old — some fossils are billions of years old. To determine the ages of these specimens, scientists need an isotope with a very long half-life.
Some of the isotopes used for this purpose are uranium , uranium and potassium , each of which has a half-life of more than a million years.
Another branch of experimental science relates to the deformation of rocks.
Moon Dust and the Age of the Solar System Answers in Genesis , the leading young-earth creationist ministry, disowns cosmic dust arguments. The most amazing thing about the cosmic dust argument is that it is still being used! It has coasted along on obsolete evidence, and nothing but obsolete evidence, for the last 25 years!! It nicely illustrates how creationists borrow from each other and never do any outside reading.
The obsolescence of this argument has been brought out in numerous debates and published in countless books, journals, and newsletters. It can be discovered by anyone who exercises his or her library card. It’s not a state secret! What does it take to get through to the creationist brain?? The earliest use of the cosmic dust argument that Van Till Van Till et al, could find was in an article by Harold Slusher, which was published in the June issue of Creation Research Society Quarterly.
Slusher made several blunders which are handed down in the “scientific” creationist literature to this very day. In the cosmic dust argument received its big kick-off from Henry Morris’ book, Scientific Creationism.
Isotopes of lead
Upon encountering a new site, the archaeologist immediately requires information about its age in order to set it in context with other sites. In research into our heritage the conservationist or architect may be able to date the general period of a building he is working with from either the situation, materials of construction, type of timber joints or other stylistic features. Almost certainly the century or portion of a century when it was built may be assigned with some certainty.
Disease started among the troops of the co-emperor Lucius Verus on the eastern borders of the empire.
The Hou Hanshu states: They resemble the people of the Middle Kingdom and that is why this kingdom is called Da Qin. They say they originally came from China, but left it. Graf , pp. For the most part, such mythological elements are so strikingly evident that they represent only a minimal problem. According to the Hou-Han shu, the Roman Empire was so named precisely because its people and civilization were comparable to those of China.
Yu believes Daxia [dat-hea] stands for the Tochari pp. It is just possible that Da Qin represents some similar process though, if this is the case, it is difficult to imagine what name it was originally intended to represent. The latter identification led Pelliot to propose that it transcribed the name of Alexandria in Egypt, of which more will be said below. What is apparently missing is anything to correspond to Old Persian initial w-, represented in Greek by the syllable Hy- the letter upsilon with spiritus asper.
Piece of copper from the harness of a horse. The Hellenistic Syria of the Seleucid kings c. At this period dynasty: All lands and kingdoms to the west of China; by extension:
How Good Are Those Young-Earth Arguments?
A special kind of radiocarbon dating: Bomb radiocarbon dating What is an isotope? To understand radiocarbon dating, you first have to understand the word isotope. An isotope is what scientists call two or more forms of the same element. But they still have the same chemical properties. Atoms of the same element that have different numbers of neutrons are called isotopes.
I don’t know how we can be sure that a crystal will exclude argon or other daughter substances except by growing it in the laboratory under many conditions.
View images by clicking on link or reduced image: Each image opens into a new window. These primitive, medium sized apes lived in rain forests between 18 and 22 million years ago. This species and others such as Dryopithecus existed before the hominid line diverged on the path to humans. This lineage ancestral gibbons is believed to have diverged from the great ape and human lineages between 17 and 25 Mya Avers, Oreopithecus ‘s hand closely matches the pattern of early hominids, with a grasping capability including firm pad-to-pad precision gripping that apes are unable to perform presumably as a response to similar functional demands to hominids Moya-Sola et al, Bipedal activities made up a significant part of the positional behavior of this primate Kohler and Moya-Sola, Gorilla and human DNA only differs by 2.
Our DNA differs by only 1. The two species of Pan, the chimpanzee, P. The human ancestral line must have arisen between 5 and 8 million years ago. However, with the many species to be found, the exact sequence of species leading to humanity, has not yet been established. Morphological differences, such as in the pelvis, supports making Neanderthals a separate species, Homo neanderthalensis.
Tiny Fossils May Be Oldest Evidence of Life on Earth
The Radiometric Dating Game Radiometric dating methods estimate the age of rocks using calculations based on the decay rates of radioactive elements such as uranium, strontium, and potassium. On the surface, radiometric dating methods appear to give powerful support to the statement that life has existed on the earth for hundreds of millions, even billions, of years.
We are told that these methods are accurate to a few percent, and that there are many different methods.
The artifacts according to today’s traditional thinking should be slowly progressing in complexity as it is thought that man is progressing in his abilities and ideas that he uses.
Radiometric dating In , shortly after the discovery of radioactivity , the American chemist Bertram Boltwood suggested that lead is one of the disintegration products of uranium, in which case the older a uranium-bearing mineral the greater should be its proportional part of lead. Analyzing specimens whose relative geologic ages were known, Boltwood found that the ratio of lead to uranium did indeed increase with age. After estimating the rate of this radioactive change, he calculated that the absolute ages of his specimens ranged from million to 2.
Though his figures were too high by about 20 percent, their order of magnitude was enough to dispose of the short scale of geologic time proposed by Lord Kelvin. Versions of the modern mass spectrometer were invented in the early s and s, and during World War II the device was improved substantially to help in the development of the atomic bomb. Soon after the war, Harold C. Wasserburg applied the mass spectrometer to the study of geochronology.
This device separates the different isotopes of the same element and can measure the variations in these isotopic abundances to within one part in 10, By determining the amount of the parent and daughter isotopes present in a sample and by knowing their rate of radioactive decay each radioisotope has its own decay constant , the isotopic age of the sample can be calculated. For dating minerals and rocks, investigators commonly use the following couplets of parent and daughter isotopes: The SHRIMP Sensitive High Resolution Ion Microprobe enables the accurate determination of the uranium-lead age of the mineral zircon, and this has revolutionized the understanding of the isotopic age of formation of zircon-bearing igneous granitic rocks.
Another technological development is the ICP-MS Inductively Coupled Plasma Mass Spectrometer , which is able to provide the isotopic age of the minerals zircon, titanite, rutile, and monazite. These minerals are common to many igneous and metamorphic rocks. Such techniques have had an enormous impact on scientific knowledge of Earth history because precise dates can now be obtained on rocks in all orogenic mountain belts ranging in age from the early Archean about 4 billion years old to the early Neogene roughly 20 million years old.
Isotopes of rubidium
Some pieces of this meteorite have proven to be “unstable” – rusting in collections. Read the newspaper account below describing the Braunau fall of On the 14th July last, a remarkable aerolite fell at Braunau, in Bohemia. Two fragments were found, one weighing fifteen, the other twenty-one kilogrammes. The aerolite appeared to proceed, as is very often the case, from a small black cloud. The smaller fragment fell upon a house, pierce the roof, struck the beam which caused it to deviate slightly from its course, passed through a ceiling composed of white clay and straw, and entered a room where several persons were assembled, but, fortunately, no one was hurt
The forelimbs were long thought to bear only two digits, but there is an unpublished report of a third, vestigial digit in one specimen.
Famous Scientists B. Thales of Miletus – Greek philosopher; developed theory of matter based upon water; recorded the attractive properties of rubbed amber and lodestone. Heraclitus – Greek philosopher; first of the Greeks to develop a theory of the human soul; he praised its creative resources and spoke of the importance of self-exploration; he spoke of the logos that is common to all and said that the universe is ruled by logos; he always urged that close attention be given to the polarites and concealed structures emodied in language.
His famous claim that an idividual can and cannot step into the same river twice reveals an interest in criteria of unity and identity; even though all material constituents have undergone change, it is still, in a sence, the same river. Preoccupied with change, he declared that fire is the central element of the universe, and he postulated a world with no beginning and no end Pythagoras – Greek philosopher and mathematician; held that numbers were basic to matter; the Pythagorean Theorem is named for his geometric formulation; developed atomic theory; students of his philosophy emphasized geometrical form as a basic property of atoms; developed mathematical relationships which led to musical harmony.
Empedocles – Some suggest c. To account for real change, he assumed that there must be more than one kind of matter, and he postulated four roots as elements; earth, air, fire, and water. Love and hate were considered principles of attraction and repulsion that alternately dominated the universe in a recurring cycle. Empedocles presented a kind of biological theory of natural selection in an imaginative poem, On Nature.
He also played an importqant role in the development of the Western or Sicilian school of Greek medicine.
Renaissance Now, let’s look at some specific examples. One type of atom that does not normally react is Neon. See the picture to the left. It already has the correct number of electrons in it’s outside electron layer so Neon does not react. Neon, along with Helium and Argon are known as non-reacting gasses because they do not need to react to be stable.
As a test, Von Weizsacker suggested looking for excess 40Ar in older K-bearing rocks.
At the time that Darwin’s On the Origin of Species was published, the earth was “scientifically” determined to be million years old. By , it was found to be 1. In , science firmly established that the earth was 3. Finally in , it was discovered that the earth is “really” 4. In these early studies the order of sedimentary rocks and structures were used to date geologic time periods and events in a relative way.
At first, the use of “key” diagnostic fossils was used to compare different areas of the geologic column. Although there were attempts to make relative age estimates, no direct dating method was available until the twentieth century. However, before this time some very popular indirect methods were available. For example, Lord Kelvin had estimated the ages of both the Earth and the Sun based on cooling rates.
The answer of 25 million years deduced by Kelvin was not received favorably by geologists.