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Age of the Earth - Final Version
Transcript of Age of the Earth - Final Version
Erin Roberts, Casey Niemiec, and Maddie Davidson
• Broken into 5 periods
i) The pre-scientific period
ii) The era of speculative cosmogonies
iii) The disestablishment of Genesis
iv) The catastrophist-uniformitarian debate
v) The modern period
Age of the Earth Before 1900
Modern Dating Methods
“Radiometric Time Scale” USGS June 13, 2001 http://pubs.usgs.gov/gip/geotime/radiometric.html
A. Mathez, Edmond. “Zircon Chronology: Dating the Oldest Material on Earth” Earth: Inside and Out. New Press. 2000.
Davies, Benthan. "Ice Core Basics" 1/9/2015 http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/
Radiometric dating is the most precise way of dating the Earth.
Zircon is contained within some of the oldest rocks, and produces the oldest dates measured.
Ice cores allow researchers to know more about the climate during the past.
Resistance to the Concept of an Ancient Earth
Objections Based on False Assumptions
Materials that decay radioactively can be used to determine the age of a rock.
The age can be calculated using the half-life of an isotope.
The idea to use radioactivity to measure geologic time stemmed from a British Physicist in the early 1900's. For the next half of the century, research in atoms and radioactivity led geologists to be able to precisely date rocks in 1950. In radioactive decay, an isotope will lose particles from its nucleus, which cause the new isotope to become a new element
The half-life of an isotope can be used to formulate how old it is. A half-life is the amount of time it takes for an isotope to decrease by half. The isotopes with the slowest rate of decay are the best for measuring geologic time.
Formulating the Half-Life
Half-Lives of Radioactive Isotopes
Parent Isotope - Stable Daughter Product - Currently Accepted Half-Life Values
Uranium-238 - Lead-206 - 4.5 billion years
Uranium-235 - Lead-207 - 704 million years
Thorium-232 - Lead-208 - 14.0 billion years
Rubidium-87 - Strontium-87 - 48.8 billion years
Potassium-40 - Argon-40 - 1.25 billion years
Samarium-147 - Neodymium-143 - 106 billion years
Zircon - Using it to Date the Earth
The Mineral Zircon
Zircon is a mineral that is particularly useful in dating the Earth. It is a fairly tough mineral, and does not erode easily. Zircon also can record events similar to how a tree will record events in the environment, the zircon crystals grow like tree rings.
Uranium in Zircon
Uranium can be found in zircon, which can be used for radiometric dating. Through radioactive decay, uranium produces lead. The amount of lead and uranium can tell geologists how old the mineral is. The half-life of the uranium 238 isotope is 4.5 billion years, which makes it ideal for dating the Earth. The oldest minerals were found in Australia, they were zircon and dated to be almost as old as the Earth itself.
Using Radiometric Dating on Zircon to Find the Age of the Earth
This discovery made during the 1900’s has greatly improved the ability to measure the age of the Earth. Radiometric dating gave geologists the ability to precisely date the Earth. Zircon allowed geologists to discover exactly how old some of the minerals on Earth are.Today, this form of dating is still the most accurate form of measuring the Earth’s age.
Ice Cores and Paleoclimates
Although no glaciers exist that were present from the Earth's beginning, ice cores can give insight to what past climate was like during the 1.5 million years.
Radiometric Dating in Ice Cores
Ice cores can be dated if they contain dust from radioactive isotopes. Ice from Antarctica has been seen to contain Uranium 238 in the form of dust. This allows researchers to date it the same way they would date a mineral, such as zircon, through radiometric dating.
Looking at ice cores can provide great insight to what the past on Earth was like. Glaciers build up by layers, and by drilling an ice core the layers will be exposed to see.
Thickness of an Ice Layer
The thickness of an ice layer can show the year's weather. A layer can show how much it had precipitated based on the thickness. It can also determine what that year's summer was like. A melt layer is a layer of ice that had been melted by summer, it is indicated by its lack of air bubbles inside.
Layers in an Ice Core
Air in the Ice
Bubbles of air from the atmosphere will be caught in the ice as it freezes. By analyzing these bubbles, researchers can determine what the atmosphere and climate were like. By measuring the changes in stable isotopes through the layers, one can measure the changes in temperature. The captured air can also detail what the atmosphere was made of. The gases in the air will freeze in the glacier, and can be reached once the core is removed from the glacial body.
Nearly all of the prevailing theories about the age of the Earth were only established in the last two hundred years, while many of the world’s religions have been around for millennia. The new discoveries made in geology have often created tension between science and religion. Some adherents refuse to accept these perceived challenges to their religious beliefs, while others have come to embrace the harmony between their beliefs and modern knowledge of the natural world. The following is a brief summary of the belief systems of four of the major religions and how that relates to their perspective on the age of the Earth.
a. The historical view was that the Earth’s age could be estimated by adding up the various chronologies in the Bible, and other historical records, which result in an estimated age of about 6,000 years.
b. Many of the scientific advances that led to the determination that the Earth is ancient were made by Christian scientists.
c. While the majority of Christians today accept the scientific evidence of an old Earth, there remains a sizable and vocal number of fundamentalists that insist on a literal interpretation of the Bible, claiming that science in fact does not give evidence of an old Earth.
a. Orthodox Jews hold to the view that the Earth is about 5,700 years old, based on the teachings of the Torah and the chronologies contained therein.
b. However, the majority of modern Jews agree with the scientific consensus on the age of the Earth.
a. The Quran does not explicitly describe how old the Earth is. It is similar to the Bible in that it claims that God created the Earth in six days, but Muslims believe this to be figurative language, leaving the actual answer a mystery.
b. Muslims do not quarrel about the age of the Earth, but they still largely reject the concept of biological evolution.
a. Among the major religions, Hinduism teaches an age of the Earth that is closest to that agreed upon by scientists.
b. They believe that the Earth goes through cycles of birth and rebirth over 8.64 billion year periods. These cycles are believed to have recurred numerous times over a 155.5 trillion year period.
c. Despite the somewhat-compatible time scales, the Hindu beliefs have no basis in science, and are only similar by coincidence.
A number of claims have been made by those who refuse to believe that the Earth is old, for either religious or other reasons, which attempt to demonstrate that the Earth cannot be ancient. The following are some of the most common objections used, and the scientific evidence that discredits these claims.
Amount of salt in the oceans.
It is argued that based on the current influx of salt into the oceans via runoff from the continents, the Earth must have a maximum age between 25 and 150 million years. However, these primitive calculations, while accurate, do not account for the processes that cause the removal of salt from the ocean. Salt, therefore, has its own cycle, and is generally in equilibrium, and therefore cannot be used as a “clock” for determining the age of the Earth.
Decay of the Earth's magnetic field.
It is widely understood that the magnetic field generated by the Earth has been diminishing in strength since it was first measured in the early 1800s. Some have argued that this downward trend can be exponentially extrapolated backwards in time, which would result a magnetic field so strong, that life would have been unable to exist only a few million years in the past. However, there is abundant evidence that the Earth’s magnetic field fluctuates, and indeed even reverses polarity, over time. This makes the argument that a decaying magnetic field disproves an old Earth an exceedingly simplistic notion with no basis in fact.
Recession rate of the moon.
In a similar fashion to a decaying magnetic field, it has been claimed that because the moon has been measured to be receding from the Earth at a known rate, it must have been impossibly close to the Earth’s surface only 1.4 billion years ago. Again, this is a simplistic “back of the envelope” calculation that disregards most of the other factors involved.
Erosion rates of the continents/sea floor sediment.
Another common claim made is that both the rate of erosion of the continents and the amount of sediment that has accumulated on the seafloor indicate that the Earth must have a maximum age of only about 15 million years. Once again, both of these measurements fail to consider all of the factors involved in these processes. The sediment on the seafloor is far from being evenly distributed, and rather than being deposited mostly in the wide ocean basins, sediment mostly accumulates on the edges on continents in deltas or continental shelves. Additionally, removal of sediment occurs along subduction zones, resulting in a negative flux, although occurring at non-regular intervals. For erosion of the continents, these calculations also do not take into account volcanism, accretion, or uplift of continents over time. Once again, failure to consider all components in a system results in an erroneous calculation.
Too much helium in the Earth’s crust.
The amount of helium found within the Earth’s crust is claimed to be too high if this rock is many millions or billions of years old. Helium easily diffuses out of rock due to its non-reactivity and exceedingly low density. However, helium is constantly being produced as a byproduct of radioactive decay in crustal rocks. As was the case with many of these examples, only considering one side of the equation (diffusion out of rocks) and not considering the other (creation of helium from nuclear decay) has resulted in erroneous estimations of the age of the Earth. In actuality, none of these processes, even when calculated correctly, can be used to measure the age of the Earth.
A number of false assumptions and approaches to geology are made by those trying to discredit modern science, or by those who have doubts in it. These mistakes are typically made by those with little to no scientific background, a fact that is often exploited by those trying to push a particular agenda. There are certainly still well-educated, qualified scientists that differ in a variety of ways with the most widely accepted theories of geology, but such dissention is always to be expected in science. The following are three of the most common erroneous ways that are used to either question or discredit established geology.
The one-sided equation.
The most frequent fallacious assumption made by those trying to prove the Earth is young is the consideration of only one component of a multifaceted system. Many Earth processes are cyclical, not cumulative, nor do they consist of processes of runway positive or negative feedbacks. This ultimately stems from an overly simplistic analysis of complicated systems that only calculate one component in the equation, and then extrapolate it backwards in time while disregarding all other related processes. This is known as the one-sided equation fallacy. While these arguments are not difficult to disprove, they are appealing to those with non-technical backgrounds who may be predisposed to doubting mainstream science for religious reasons. Therefore, they are frequently used to demonstrate “obvious” problems with the science, despite there being no problems at all.
Catastrophism vs. Uniformitarianism.
The contrast between these two interpretations of the geologic record has defined much of the debate over the past several hundred years on how the Earth was formed. Two hundred years ago, most scientists subscribed to the notion of either catastrophism or stasis as the two explanations for the Earth’s appearance. Catastrophism attributes nearly all geological features to a small number of large-scale or global catastrophes; stasis is the idea that the way the Earth is now is how it always has been either since its creation, or since eternity past. Such viewpoints were appealing explanations for how things like “drift” could be observed far from the oceans or how seashells could be found on the tops of mountains. However, once the processes that continue to form the Earth became better known, it became evident that the vast majority of the geologic record could be explained by the action of slow, gradual processes over vast periods of time. It is frequently either misunderstood or misrepresented by those who resist the notion of uniformitarianism that this principle precludes the possibility of catastrophes, which is untrue. Catastrophes are part of the normal geologic cycle, and their influences are evident in the geologic record, but aside from exceptional events (such as supervolcanic eruptions or asteroid impacts), their scale is typically never global.
Supernatural vs. Naturalistic.
The final dominant erroneous approach that has been taken towards science over the years, and still continues to some extent today, is the notion that some phenomena can only be explained by invoking a supernatural force that is not observable or repeatable. In the early days of the development of the science of geology, much resistance was given to the explanations being offered by scientists on the origins of the Earth. It had been long assumed by Christians that the only explanation for the physical world and all of its associated unexplained phenomena was that God created it that way. When geology began to offer explanations for many of these Earth processes, it was seen as an attack on the church, despite the fact that most of the scientists who introduced these theories were Christians themselves. As was seen in the summary of several of the world’s major religions, most people of a religious nature today have no issue with reconciling their beliefs with the discoveries of science.
Casey Niemiec: Resistance to the Concept of an Ancient Earth
Albritton, C.C., 1993. The Earth Sciences. Encyclopædia Britannica. vol. 17, p.618
Baker, V.R. 1998. Catastrophism and uniformitarianism: logical roots and current relevance in geology. Geological Society, London, Special Publications. vol. 143 p. 171-182.
Huda. Creation of the Universe. Accessed online 5/4/2015 http://islam.about.com/od/creation/a/creation.htm
Lienhard, J.H. 1998. The Age of the Earth: Science, Religion, and Perception. Shell Distinguished Lecture Series, University of Houston. Accessed online 5/8/2015. http://www.uh.edu/engines/shell.htm
McGillivray, R. Ocean Salinity as a Failed Scientific Clock. Accessed online 5/7/2015.
Mellem, K. Ocean Floor Sediment as a Creationist Clock. Accessed online 5/7/2015. http://apps.usd.edu/esci/creation/age/content/creationist_clocks/magnetic_field.html
Hinduism: Age of the earth according to Vedic chronology. Accessed online 5/8/2015. http://www.bhakti-yoga-meditation.com/hinduism-age-of-the-earth.html
Tiscareno, M. 1999. Is There Really Scientific Evidence for a Young Earth? Accessed online 5/4/2015. http://www.lpl.arizona.edu/~matthewt/yeclaimsbeta.html
The Five Periods
Universe is finite and spherical
The Earth had a stationary “earth” at the center
Believed the whole universe was enclosed by a sphere of “Prime Motion”, which was turned by the “First Unmoved Mover”
Unchanging planets, a moon and a sun where believed to be contained within transparent spheres.
Father of Aristotelian science
Clement and Origen
185- 254 AD
Originated from Alexandria, had the intentions of reconciling Greek wisdom
Beloved Aristotle’s views and thoughts could be over ridden with scriptural wisdom
Imagined what expanded to “five senses Concordism”, believed in separate moral, literal and spiritual Bible passages.
Accepted Van Bebbers view “this allegorical interpretation gave birth to a new brand of Christianity”
Mixed culture, philosophy, theology
Tried to change the equalization of the Church and written scripture, recognized in Catholic theology
Influenced Thomas Aquinas (1224-1274 AD)
Greek Philosophy was reborn and Aristotle's ideas on philosophy and science were reaccepted
Roman Catholic theology and tradition were reinforced
Acceptance of the idea of earth-centered cosmos
Erin Roberts: Modern Discoveries
Maddie Davidson: Age of the Earth Before 1900
Harter, Richard. "Changing Views of the History of the Earth" http://www.talkorigins.org/faqs/geohist.html 6/1/1998
What Were Galileo's Scientific and Biblical Conflicts with the Church?" GALILEO. ChristainAnswers.net, n.d. Web. May 2015. <http://christiananswers.net/q-eden/galileo.html>.
Before AD 1600
Relied heavily on the biblical account in Genesis
Genesis was used to date the Earth
Greek philosophers’ views such as Aristotle and Galileo, were accepted widely without question
Europe in 1600 AD- history of the Earth was explained and accepted by Genesis, the Earth was 6000 years old, compared to Europe in AD 1900- believed the Earth was ancient, the Noachian flood did not exist, and that Genesis was an allegory and not literal history.
In pre-scientific period there was largely questions about the Earths’ age. These questions were mainly theological. The rationality of Genesis was questioned due to its inclusion of miracles and acts of God. Ussher and Descartes required a rational explanation and in 1637, Descartes had a highly influential cosmogony. In 1640 Ussher calculated that the Earth was created in 4004 BC. Descartes understood the biblical date compared to Ussher who accepted the biblical date, but biblical genealogies and historical records were largely what he relied on for his evidence. Ussher believed the Earth had not changed much and was created as it is now, whereas Descartes believed in the physical history of the Earth and did not agree with the biblical timeline of creation in 6 days.
The Pre-Scientific Period
The Philosophers' Views
1473- 1543 AD
Very well educated in law, theology, math, metaphysics, languages, and astronomy
Changed the earth-centered cosmos views, and created cosmology with sun at the center
Also introduced the Earth rotating on a polar axis, and the Earth and planets orbit the sun
Renaissance period, educated in the classics
In 1610 he built his own telescope, he was 46
His focus was physics not astronomy
He studied the moon and saw valleys, mountains and various other change indicating topography
He challenged the foundations of the Aristotelian cosmos
Jupiter's’ moons are named Galilean moons, because he studied the motion of the four moons
He watched the phases of Venus, and through these discoveries he excluded the idea that there were heavenly bodies revolving around the earth
His ideas supported Copernican cosmos
The Era of Speculative Cosmogonies
Before 1600 AD
Cosmogony is a branch of science that focuses on the origin of the universe, specifically the solar system
The Earth was believed to be square and flat
Cosmogonies were believed to be “rational” thinking about the Earth
Relied on field geology rather than cosmogony
The evidence of Earth’s topographical changes began to be recognized
The Noachian Flood was largely proposed as an explanation for the topographical changes
It was suggested that strata was deposited by the sea and the land changing places over time
Earthquakes and volcanoes were evidence of crustal transformation
Erosion due to rain, wind and sea were observed in action, thus leading to the discovery that these actions were capable of creating valleys and carving mountains
The 1700s brought the depletion of the idea that the Earth is 6000 years old. Estimates were calculated and in 1774, Buffon thought it to be 75,000 years- to several billion years old. People began accepting the geological evidence of the changes in the Earth. They saw the Earth had been covered by land and then covered by seas, the degree of sedimentation, and mountains had a long history of slow deformation. Erosion was also accepted as the cause for shaping the Earth over time
The Disestablishment of Genesis
The Catastrophist-Uniformitarian Debate
The end of the 18th century brought the concrete idea that the Earth had varied over a long period of time
The idea of cosmogony was revived
Cuvier believed that the history of the Earth was caused by major catastrophic events
Uniformitarians such as Hutton and Lyell, believed that slow uniform changes in the Earth caused the history of changes of the Earth
Geology and Genesis were reconciled back into thought because spiritual geologists were prominent, but by 1830 they were overruled by the science community
Uniformitarians believed the Earth was indefinitely old.
Catastrophists disagreed with the rate of change and the kinds of change that occurred over time.
Uniformitarians persuaded the community with their evidence and ideas, and overstated the degree of gradualism
The importance of catastrophes was minimized
Massive expansion of knowledge on the history of the Earth
In the mid 1800’s sedimentation rates and other geophysical phenomena were studied to attempt to date the Earth. Estimates ranged from 100 million years to several billion years. Geological history was being reconstructed, making it harder to get accurate dates. As well as the rates of physical process were not understood deeply.\
The late 1800’s was a time of expansion through the physics world. Physicists made new estimates of the Earth’s and Sun’s ages. Two main questions asked among scholars:
-How long would it take for the Earth to cool from its initial heat of formation to its present temperature?
-How long had the Sun been shining, considering the energy sources at the time?
Kelvin made expansive discoveries and in 1862 dated the Earth at 98 million years old using a model of the rate of cooling. He estimated the minimum age that was consistent with the geology. In 1897, he revised his date to 20-40 million years, but because of his lack of knowledge in radioactivity and the heating of the Earth’s crust by radioactive decay, his dates were completely incorrect. He also had a small number to estimate the age of the Sun, these estimates did not match geology. Einstein's theory of relativity was eventually developed and explained how the sun had been shining.
1905 radiometric dating had been performed, and concluded the Earth was several billion years old. Currently the estimate is 4.55 billion years.
The Modern Period