Sunday, October 06, 2019

Geology Through Literature - Good Omens

Geology Through Literature: Good Omens

As I wend my way through the 100 Greatest Books of all time, I often come across geological references within them. This one was a bit of a different one, because of the nature of the authors, the geological reference is more comedic in spirit and not meant to be taken literally. 

The book starts off with the history of the Universe, or the history of the Universe as it needs to be for this book (keep in mind, the authors are not serious, this is entirely a joke).
"Current theories on the creation of the Universe state that, if it was created at all and didn't just start, as it were, unofficially, it came into being between ten and twenty thousand million years ago. By the same token the earth itself is generally supposed to be about four and a half thousand million years old. 
These dates are incorrect. 
Medieval Jewish scholars put the date of Creation at 3760 B.C. Greek Orthodox theologians put Creation as far back as 5508 B.C. 
These suggestions are also incorrect. 
Archbishop James Ussher (1580-1656) published Annales Vetoris et Novi Testamenti in 1654, which suggested that the Heaven and the Earth were created in 4004 B.C. One of his aides took the calculation further, and was able to announce triumphantly that the Earth was created on Sunday the 21st of October, 4004 B.C., at exactly 9:00 A.M., because God liked to get work done early in the morning while he was feeling fresh. 
This too was incorrect. By almost a quarter of an hour. 
The whole business with the fossilized dinosaur skeletons was a joke the paleontologists haven't seen yet."

The age of the Universe has been a work in progress for the the entirety of the Scientific Revolution and long before that. As Good Omens states, scientists do actually place the origins of the Universe between 10 and 20 billion years ago. The age of the Earth has also been a work in progress since people started to wonder about such things. There are multiple people who have been influential in determine the age of the Earth, both in good ways and in bad. The following is a list of people and their contributions to the age of the Earth.

- 1654: Lord Ussher - Lord Ussher used the Bible to determine the age of the Earth back dating the ages of the people mentioned in the book and calculated out that the Earth was born in 4004 BC. Ussher used the death of King Nebuchadnezzar as a reliable date from which to start and worked backwards from there using the Bible as his only "reliable" source of of information. He eventually worked backwards to get a final date of October 23rd (not the 21st as Good Omens proclaims), 4004 BC. The date itself was based on Ussher's assumption that since the Jewish calendar begins in Fall, and the week obviously started on a Sunday, he picked the first Sunday following the autumnal equinox in 4004 BC. The equinox itself has shifted through time on the calendar due to inaccuracies and adjustments, so that explains the October equinox and not the typical September one.

- 1788: James Hutton - James Hutton, often touted as the Father of Geology, developed the Principle of Uniformitarianism, which stated that the present is key to the past and that all processes happening on Earth today are the same ones that happened on the Earth in the past. This means that when we have ripples and mud cracks in modern day sediments, they can help us identify ripple marks and mud cracks in the rock record. Since everything happening today has happened in the past and erosion and deposition are incredibly slow processes then the age of the Earth must be very, very old. Although he couldn't be sure of an exact age of the Earth, one could easily assume the Earth was millions or even billions of years old based on the rates of modern day erosion and sedimentation.

- 1800's: Following Hutton several scientists tried to quantify the rate of sedimentation to calculate the age of the Earth from these rates. The ages produced ranged from several 100 million years to billions of year. Unfortunately though, the lack of constants, such as inconsistent rates of sedimentation, and limited knowledge of the entirety of the rock record at the time, made such estimates fraught with errors and miscalculations.

- 1862: Lord Kelvin - Taking a step back from Hutton's immensely old estimate, Lord Kelvin as an expert in thermodynamics, entered the picture. Lord Kelvin determined that the Earth must have formed from a molten state and slowly cooled through time. Knowing the size of the Earth and the rate of cooling, as well as the current estimated temperature of the Earth, he was able to determine that the age of the Earth was between 20 and 100 million years old. Lord Kelvin did have a significant blind spot in his calculations though because it wasn't discovered yet: radioactivity. The process of radioactivity releases heat as elements decay and the Earth is riddled with radioactive elements, which are able to slow the rate of cooling and also provide an internal source of heat for the Earth.

- 1897: Henri Becquerel - Not directly tied with the age of the Earth, Becquerel discovered one of the primary driving forces for future age dating research, radioactivity by the emission of x-rays from uranium salts.

- 1902: Marie Curie - Also not a person working directly on determining the age of the Earth, Marie Curie's work on radioactivity propelled Becquerel's discovery into the realm of future possibilities. Her work with radioactivity helped to explain the phenomena and enable scientists to use it for age dating. Radioactivity is the process by which unstable atoms (termed the parent elements) eventually decay down to stable atoms (termed the daughter elements). This decay, that takes place in the 1-to-1 ratio (1 parent decays to 1 daughter) enabled future scientists to count the number of parents and daughters and use the ratio to determine the age of rocks on Earth. The decay of these elements occurs over a set period of time known as a "half-life". The half life of a radioactive element is the amount of time it takes for half of the parent to decay to the daughter. These half-lives were determined to be very stable and are what makes radioactive dating possible. The discovery of radioactivity and the release of energy from these atoms invalidated the vaunted Lord Kelvin's predictions.

- 1904: Ernest Rutherford - Rutherford was one of the the first to recognize the potential of radioactivity to be used for dating, very shortly after Curie's discoveries. His calculations for determining the Earth's age dated the Earth using the decay of Radium to Helium, which produced results initially at 40 million years (Ma). His dates were then revised to 140 Ma (1905), and eventually to 500 Ma (1906).

- 1905: J.W. Strutt - Using similar methods to Rutherford, Strutt was able to produce results giving an age of 2.4 Ga (billion years). Although, by now it was recognized how poor an estimate the Radium-Helium dating methods was because Helium, being a gas, could leak out of the mineral. This would end up producing a caluclated age far less than what they likely were.

- 1907: Bertram Boltwood - Having realized the problem with the Radium-Helium decay pair, Boltwood suggested using Uranium-Lead, which would produce far less leakages. His age estimate of 2.2 Ga however was found to have problems since several elements also produce lead and would inflate the age estimate.

- 1920's: During the 1910's through the 1930's various scientists bounced around with the age of the Earth from several hundred million to a few billion years. Some by estimates based on other people's works and some on new methods of radioactive dating, but nothing concrete was able to be determined.

- 1929: Edwin Hubble - An astronomer focusing on the stars, Hubble came about the age of the Universe, not just the Earth, from a different direction. Hubble noticed that distant galaxies were all moving away from us, producing a shift in the light patterns that we see here on Earth. This shift in the light patterns was termed the "red shift", based on the pattern that the star's light produces. He also noted that the further the galaxy is away from us, the faster it was moving away from us. He determined that all the galaxies were moving away from each other, and if all of the galaxies were moving away from each other, then at one point in time they would all have to have been in the same location. This led to the Big Bang Theory that states that the entire Universe started as a great explosion some time in the past. Looking at the rate at which the stars were moving led Hubble to estimate that the age of the Universe was 2 billion years old. This was a problem, given the dates that have already been produced for the age of the Earth at the time were similar, if not older.

- 1941: Alfred Nier - Throughout the 1930's, Nier and his colleges determined that the different isotopes (isotopes are different weights of individual elements) of lead were produced from different sources. Some had no radioactive sources and others were produced by different isotopes of Uranium or Thorium, all of which have different half-lives. This allowed researched to determine the age of a rock just based on the average abundances of the different Lead isotopes. Using this information Nier produced an age of 2.57 Ga from the oldest known rock at the time, the Huran Claim Monzanite.

- 1946: Arthur Holmes and F.G. Houtermans - Holmes and Houtermans expanded upon Nier's research and developed plots showing how these Lead-Lead percentages could be used to calculate out the age of the Earth. From this information they were able to date the age of the Earth back 3.35 Ga.

- 1950's: Reevaluations of Hubble's luminosities in the 1950's corrected for Hubble's age dates, giving current astronomers an age range of 10-20 billion year age for the Big Bang. Which was a much longer time than the current estimated range for the age of the Earth. Many scientists were happy about this because it is difficult to find a case where the Universe could be younger than the Earth. Further refinements have narrowed that range to ~13.8 billion years for the Age of the Universe, based on improvements in the determination of this rate of expansion (

- 1953: Clair Cameron Paterson - While trying to figure out the age of the Earth, it had been determined that the oldest rocks on Earth were a problem to find. Over time the Earth eats its older rocks producing newer rocks, leaving fewer and fewer really old rocks behind. So, over time, the amount of rocks from the origins of the Earth became rare to the point of non-existent. It was also determined that if the Earth and the Solar System formed at the same time, then the date of the oldest material in the solar system would be the same as the age of the Earth. So scientists started looking outside the Earth for rocks that formed elsewhere. The perfect place to look came in the guise of meteorites, extraterrestrial rocks located right here on Earth. C.C. Paterson proceeded to calculate the age of the Earth using several different meteorites across the planet. Using the Lead-Lead age dating technique developed earlier, he determined an age for the Earth at 4.5 Ga. This is an age that has since been confirmed, and refined, by many other scientists using many other methods.


Possible Educational Activity

Calculation for the age of the Earth is obviously not limited to just Good Omens, it is a geological theory that has been around for some time and knowing the scientific age of the Earth is frequently a fact given out in grade school. However, the determination of that age is often overlooked by many people and I am sure there are not many people who can tell the process by which the age of the Earth was finally discovered, or even who was the scientist credited with the calculation. So for an educational assignment I suggest having people look up several of the people associated with calculations for the age of the Earth, what processes did they use, what were their limiting factors, and what assumptions were made that may limit their calculation's validity.  


Faure, Gunter. "Principles of isotope geology, second edition." (1986).

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