February 26, 2018.
As was mentioned in the previous post, by the end of the 19th century, the vast majority of geologists were convinced that the earth was much older than a few thousand years, and even the majority of Christians had come to terms with an ancient earth. Many lines of evidence told geologists and paleontologists that the age of the earth was much older than what was once thought. With the advent of radiometric dating in the 20th century, timetables became even clearer. I would like to stress here again that these geologists did not start from an “atheistic” stance and set out to prove that the earth is much older than the bible says it is or that the Genesis flood didn’t happen. Many tried to reconcile the data with the flood model until it became all too apparent that the data simply did not fit the paradigm. Here, I would like to go over some of the evidence for why scientists believe in an old earth and an even older universe. We will start with non-radiometric methods since radiometric dating is heavily criticized by young-earth creationists, though their grounds for criticism are all but unfounded (we will explore some of the most common objections in the fourth section). Then we will move on to radiometric dating, which has decisively settled the question of the age of the earth before moving on to the evidence of the age of the universe. Again, all I ask is that you keep an open mind when looking at the evidence
Non-radioactive dating methods
It should be noted that these methods do not give an absolute age of the earth, only lower limits of what that age could be. For example, if I count 2,000 rings in a tree stump, this doesn’t mean that the earth is 2,000 years old, but rather the earth is at least 2,000 years old. Absolute dating will be discussed in the next section.
The first line of evidence will probably be the easiest to visualize. I would assume that most if not all of us know that we can count the rings on a tree stump to tell how old the tree was before it was cut down. This is due to annual bark growth cycles that leave a distinct record of years that the tree has been alive. So, what is the youngest age the earth could be based on tree rings? At least 11,400 years before present. The oldest known living bush is thought to be 11,700 years old based on ring estimation. Finally, there was a study done in Southern California that used tree rings to estimate one tree clone to be over 13,000 years old.
13,000 years might not seem that old when we are contemplating the age of the earth, but remember this method only tells us the lower limit of the earth’s age. Further, because trees are living entities, they can only survive for so long. To go back further, we must turn to other counting methods. Much like the rings on a tree, in regions that are very cold such as Antarctica and Greenland, annual layers of snow are deposited and form countable layers of ice. Ice cores can be drilled out and the annual layers can be counted to date the layers of ice. Many studies on ice cores have been done for various reasons and have consistently produced ice layers that are much older than 6,000-10,000 years. Ice cores have been dated to 42,000 years before present (bp), 110,000 years bp and 123,000 years bp.
Many lakes lay down annual sediment layers that vary from season to season in texture and composition, and because of this, they can be counted. Annual sediment layers are called “varves”. Both varves and tree rings are used in calibrating carbon-14 dating (see radiometric dating section), and thus have been often studied. One study counted varves from Lake Suigetsu in Japan and found that they were able to date back at least 37,930 years. This is not even the most impressive. Other studies have taken samples from Lake Baikal in Russia and were able to date cores back to 2.5 million years ago (ma), 3.5ma, and even up to 12ma.
This is just the tip of the iceberg for non-radiometric dating methods that have been found and put to good use to both verify and calibrate radiometric dating methods. These methods give us information about the climate and atmosphere at the time-based. Remember, these are methods of physical observation. There are many other methods, but for the sake of brevity, I am not including them. What’s more, these observations do not show any record of a recent worldwide flood, which would be expected to be seen in the record. The interested reader is invited to check out this article from the Journal of the American Scientific Affiliation for more information and sources.
1. What is radiometric dating and how does it work?
The dating methods listed above are used by geologists and paleontologist in various ways to gain information about different annual climate or atmospheric characteristics over the recorded past. However, they are not used very often for absolute dating of rocks or other ancient specimens. For absolute dating, the major method that scientist use is radiocarbon dating. If you are reading this, it is likely that you already know about or at least have heard about radiometric dating. If there is any point that is hotly contested by young-earth creationists about dating, it is radiometric dating. However, this kind of dating is bedrock (pun intended) to geology, much like the theory of gravity and mechanics is foundational to astrophysics. Much work has been done to confirm time and again that the dating methods work well and when there are issues with a given sample (such as isotope leaking), the methods/mechanisms that might render a radiometric date incorrect are well known and can be identified by trained professionals. But before we get into some of that, it is important that we go through a quick overview of radiometric dating to get familiar with the basics of this type of dating.
The theory and application of radiometric dating has been described in detail in a multitude of different sources, many of which will give a much better overview and deeper insight into the dating method than is my intention here. However, I will describe the theory briefly here. Radioactive decay is a physical property of radioactive elements that can be exploited as a built-in timekeeping mechanism in various samples of ancient matter that contain these elements. Elements are made up of atoms that contain a certain number of protons (which corresponds to the atomic number of the element), neutrons and electrons. The number of protons an atom has determines which element it is; for example, an atom of carbon always has 6 protons in its nucleus and an atom of gold always has 79 protons in its nucleus. Elements can have varying numbers of neutrons in its nucleus, which often gives rise to several different isotopes of a particular element. For example, there are three naturally occurring isotopes of carbon: carbon-12 (6 protons, 6 neutrons), carbon-13 (6 protons, 7 neutrons) and carbon-14 (6 protons, 8 neutrons). Some isotopes are stable and do not change over time, such as carbon-12 and carbon-13. Other isotopes are unstable and undergo stochastic (random) radioactive decay in which the element spontaneously changes into an element with a different number of protons and neutrons. This decay can happen through several different mechanisms such as alpha decay (the loss of two neutrons and two protons) and beta decay (such as electron emission or electron capture). This change is recorded in the ratio of parent isotopes (the original element) to the daughter isotopes (the element that has been formed during the decay process) in a given sample. The time it takes for half of the parent isotope to decay into the daughter isotope is called the half-life of the element. Though the decay of a single atom of an element is random, the decay rate for any given isotope can be statistically modeled (since there are millions of atoms in a very small sample) with great accuracy, and the half-lives of many different elements have been precisely determined.
Each element has a different decay constant, which gives a first-order rate law of
where N is the number of daughter isotopes, N0 is the number of parent isotopes, k is the decay constant and t is time. The rate constant is determined by the half-life via the equation t1/2=ln(2)/k. The half-lives of different isotopes have been experimentally determined, and the rate constants of many different isotopes have undergone many tests that have shown them to be constant even under extreme environmental conditions, and even when there have been shown to be slight variations in the decay constant, the variations are very small (not enough to even remotely reconcile the ages in a young-earth framework) and occur via known mechanisms. Further, Young and Stearley have reported that “to date, no evidence for perturbation in the decay constant of any geologically important radioactive isotope has been found.”
Radiometric dating, then, can be used to determine the date of formation (or death, in samples of organic matter) based on the half-lives and ratios of different elements found within the sample. There are a multitude of different radiometric dating methods that are employed in geologic, archaeologic and paleontological dating depending on the type and estimate age of the material being tested, and often multiple methods are used on the same sample to determine the precision of the dating.
2. Types of radiometric dating
There are many different types and methods of radiometric dating that have been developed over the years. Some of the choice of method has to do with the estimated age of the sample that you are testing. For example, the half-life of carbon14 is about 5,730 years. For dating methods to be accurate, there needs to be enough parent and daughter isotope in the sample that is able to be precisely quantified. For this reason, after 8 or 9 half-lives (or ~50,000 years), there would not be enough carbon-14 in a sample to reliably date the sample. Thus, carbon-14 dating cannot be used to date samples that are older than 50,000 years old. The there are other dating methods that use isotopes that have much longer half-lives, such as uranium-238 which has a half-life of 4.47 billion years.
If you have been in this discussion for very long, you probably have either seen or heard the obvious problem in this dating. How does anyone know the original number of parent isotopes in the sample, especially since these samples are claimed to be very old. This was actually the way my younger self easily dismissed the issue of radiometric dating out of hand. However, I assure you that if a high school Walter with very little knowledge of radioactive decay and dating methods is astute enough to point out this “obvious” problem, then the people who do this dating on a regular basis are well aware and equipped to deal with it. And so they have (which should really be expected, since radioactive dating is one of the foundational principles their discipline). Some of the dating methods, such as carbon-14, are easy to estimate the amount of parent isotope in the sample because it is correlated with the amount of carbon-14 in the atmosphere today. When an organism is alive, it continuously takes in all the carbon isotopes in the ratio that they are present in the atmosphere. When the organism dies, it stops replenishing the amount of carbon-14 and the clock is started as the amount of carbon-14 in the organism begins to decay. Thus, if we take the amount of carbon-14 the sample has left and compare it with the amount it would have had when it died, we can get an accurate time frame for when the organism lived.
You might say, “Well, how do we know that the amount of carbon-14 in the atmosphere hasn’t gone through changes over the years?” This too was one of my early key dismissal points. However, the carbon-14 levels have been calibrated for the past 50,000 years based on data from tree rings, plant macrofossils, speleothems, corals, and foraminifera. The studies listed above in the non-radioactive dating methods are not typically done in order to ascertain the old age of the earth (geologists are already convinced on that point), but rather to gather data to calibrate radioactive dating methods. Further confirmation can be done by comparing radiocarbon dating for materials of known dates. We can also compare radiometric dating methods on the same sample. Contrary to some rhetoric espoused by people who are not in the field, radiocarbon dating has been well established and can be trusted.
Scientists have even gone further and developed methods of radiometric dating that do not rely on any assumptions of the original value for a parent isotope, but rather derives that initial value mathematically. This method of dating is called isochron dating and actually assumes that we do not know the original ratio of parent to daughter isotopes in the original formation of the sample. Isochron dating uses the ratio of radioactive isotopes to non-radioactive isotopes of the same element, from which a straight line can be drawn to determine the initial ratio of parent to daughter isotope. It is not my goal here to explain the details of this, or any other dating method, only to say that geologist have developed many ways to deal with the real world problem of dating old samples. For a much more detailed account of isochron dating, see this article from talkorigins.com. Suffice it to say here that radiometric dating has proven to be very reliable and there are different methods of addressing the natural problems that arise in dating.
3. Convergence of different methods
Now that we have a very, very basic understanding of how radiometric dating works (the interested reader is encouraged to check out the listed sources for more detailed descriptions), let me make a couple of observations and reasons for why we know the age of different samples and of the earth with a good amount of certainty. From the information above, I hope I have made it clear that scientists have adequately addressed all the “problems” of radiometric dating, and their precision has been confirmed time and again. But perhaps one of the most telling lines of evidence for this is when many different dating methods converge on the same date. I have said before that the technique of using multiple dating methods with different isotopes is routinely used to cross-check the estimated dates of samples. Thus, we can be confident when multiple lines of evidence converge, agree with other lines of evidence (such as stratification and non-radiometric dating methods), and even with other lines of evidence from other disciplines (such as paleontology and genetics), that we are ascertaining a very reasonable truth of the age of a sample. I contend that if there weren’t a priori reason that people had to reject the concept of an old earth, the matter would be more settled than many other scientific questions that have even less evidence backing them up, yet have overwhelming support from the public.
But what does this say about the age of the earth? Dating rocks on the earth cannot give us an absolute date for when the earth was formed since we don’t know which rocks are the oldest on earth, if there are any rocks older than those that have been dated at present, and because the earth constantly recycles and reforms rocks. However, dating rocks can give us a lower limit for the age of the earth. Rocks on earth have been dated back to 3.8 billion years, and the oldest rock that has been found on earth currently is dated to just over 4 billion years ago. On the basis of dating meteorites that are reasonably assumed to have been created at the same time that the earth was created (which is further confirmed by an isochron plot of terrestrial and meteorite samples), scientists have dated the formation of the earth to be around 4.5 billion years ago.  Many different measurements and dating methods have been used to date these rocks, and all the methods and measurements converge on the same answer. This gives us more than ample reason to believe that the measurements are trustworthy.
Dating the Universe: Light from afar
Beyond the question of dating the age of the earth, another claim that has been made from the discipline of astrophysics and likewise hotly contested by young-earth creationists is that the universe is about 13.7 billion years old. It would be very difficult to go into the physics of the evidence that the astronomers put forth to give a compelling case that the universe is this old, and the interested reader is directed to reference 30 for a full, detailed account of the evidence. We will hit on some high points here, as I don’t think it’s as hard to swallow a very old date for the universe once one has come to terms with the concept of an old earth, discussed above.
Before I briefly summarize the astronomical evidence of an old universe, think with me for a moment about light and stars. When we look up at the night sky and see the wonders of creation, we are looking at stars and are millions, if not billions, of light years away. We know the distances to stars based on tools from geometry (such as the trigonometric parallax) and such measurements as apparent and absolute brightness of the stars. If these stars are millions of light years away, the logical conclusion is that the universe is at least as old as the time it has taken for the light to travel the vast distance.
To summarize the evidence that David Weintraub gives in his book How Old is the Universe?, four overall, completely independent lines of evidence indicate that the universe is 13-14 billion years old: cooling times for white dwarfs in the Milky Way, turn-off points for globular star clusters, the expansion rate of the universe and the cosmic background radiation power spectrum analysis. There is no way I could briefly explain the reasoning here as there is not ample space (Weintraub writes a whole book on these topics) nor am I well versed in astrophysics. However, I do want to stress that these are four completely independent measurements than all yield the same answer. Weintraub concludes his book with this thought:
Now we have four independent methods for deriving an age for the universe, and all four yield a consistent answer. If the age derived by any one of these methods were presented by itself, we might reasonably wonder whether to believe the claim. Taken together, however, we now have extremely strong evidence that the universe is indeed 13.5 to 14 billion years of age.
The strong evidence is why most astronomers (who do not have an a priori reason to reject an old universe) agree that the universe is around 13.7 billion years old. It did not come from a malicious spirit to try to distort the truth. Quite the opposite. Astronomers are led to this answer because that’s where the evidence takes them.
1. Created with the “appearance of age”
Perhaps one of the biggest reconciliation of the data and young-earth creationism is to say that God created the universe and the earth with the “appearance of age”. This was my answer for a long time, as it seems to nicely explain geological formation and biological data (if God created a tree on day three, and I chopped it down on day four to count the rings, I might easily count 200 years’ worth of rings- but the tree would actually only be one day old). However, this line of logic starts to break down upon further examination.
First, let’s point out something that this argument automatically concedes: the evidence of an old earth and old universe are assumed to be correct. This actually could be a good compromise for those who want to hold to a young-earth model to get along with those who hold an old earth model. But the problem comes when they still get mad and try to teach that the data points to a young earth. If the universe was created with the “appearance of age”, then a young-earth creationist should have no problem with an astrophysics saying the universe is 13.7 billion years old. They should actually agree that that’s what the data say. They just choose a different paradigm as to why the data say that. However, this is not typically the case (probably for good reason, as we will soon see).
Secondly, at the surface level, this seems like a good answer to the data. However, if you truly take this position, you can’t really prove much of anything in terms of the “actual” age of the earth. It is theoretically possible that God created the earth and the universe last Thursday, complete with all of our history and memories. There is no way you can falsify that claim. It could be true, just as God could have created the earth 6,000 years ago, complete with all the fossils and geologic structures in place. However, this is not a scientific idea, but one that would be taken on faith or philosophical grounds. Just like the first point, there is no reason to argue with science if this is the case.
However, the final point here I think is the key (and one we will return to and flesh out more in a later post): If God created the universe with the appearance of age, yet expects us to deny the observable evidence for the age of the earth, then it would seem that God is a deceiver. There was a heading in Francis Collin’s book The Language of God that first hit me with this idea, and it made a lasting impact. Why would God make it look like what all the scientific evidence points to if that is not actually what happened? Why would he plant false evidence (knowing that we would find it!) and expect us to reject it? Why would he make us rational beings and then expect us to throw off rationality? Under this idea, God would have had to plant fossils of animals who never lived in the ground, create light in mid-flight (and from stars that never even existed for us to observe supernovas) and sediment layers in lakes that were never actually laid down. Perhaps this doesn’t amount to a dilemma in your mind, but it certainly does mine. I do not believe, on theological grounds, that this is the character of God. Instead, I celebrate the evidence he has given us of his good creation, even if it didn’t fit my preconceived notions (based on traditional interpretations) of how he did it.
2. Changing decay rates
Many young-earth creationists do not push the appearance of age idea because of the known problems and theological dilemmas that come with it. It is more often that young-earth creationists attack the science. One of the main attacks on the dating methods is the proposition that radioactive decay rates are not constant, or had not always been constant. If this were the case, it certainly would pose a problem for radiometric dating. However, as I said above, the decay rate has been tested under many different, very harsh environments, and shown to be constant. In cases where the rate has been shown to vary, the variation is extremely small and would not account for a 6,000-10,000 year old earth by a long shot. Further, these very slight variations have not been shown in geologically relevant isotopes. However, it has been said before that the proof is in the pudding. If the decay rates of radioactive isotopes did not remain constant, then consistent answers would not be routinely given for dating using different methods. Cross checks with other dating methods (such as tree rings) would not show consistent results. Isochrones wouldn’t fall on a straight line. In short, there are easy ways of checking the dates given by radiometric dating, and these have shown consistent results. Further, I described methods in this article that do not use radiometric dating to show the earth is older than a few thousand years old. For more information about the reliability of radiometric dating, see this article by G. Brent Dalrymple.
3. The flood challenges all assumptions
A common rhetorical method that I used when I was in the young-earth camp was to say that our interpretation of the data depends on our starting assumptions. If we started with the big-bang, evolution model assumption of the universe, we would explain the data in one way, whereas if we started with the creation, flood model, we would interpret the data in another way. Many young-earth creationists us the flood to “fix” all the problems that geologic data give. However, this cannot be the case. First, as we have seen, even under enormous amounts of pressure, radioactive decay rates do not change. Secondly, a year-long catastrophic worldwide flood cannot explain sediment and ice layers that were laid down slowly over thousands or millions of years. Third, why about all the trees that would have died being under a very large amount of water for a full year? How would we find living trees that date back before the time period of the flood based on their rings? I contend that you can’t point to an event and vaguely say “well, the flood could have changed the assumptions of the data,” without at least a mathematical theory that would explain the data in light of a world-wide flood. That’s not an argument from science.
4. Other objections
There are many other objections that young-earth creationists throw out confidently why the entire science of chronological dating is wrong. I do not have the time or the expertise to deal with them here. Fortunately, however, they have been addressed over and over by the people who do have the expertise to do so. Often the claims made by young-earth creationists are simply rhetoric designed to make the non-technical reader believe there actually is much doubt in the scientific community about the claims of an old earth. Let me be clear: there is not. The only people who make this claim are those who have an a priori reason to do so, which should at least give you pause. Often, they take scientist’s quotes out of context and make it seem like they are saying the exact opposite of what they actually said. Finally, many of their claims are just straight false. I don’t mean to imply that they are purposefully saying false statements (at least I certainly hope not), but it must be said that much of the rhetoric from the young-earth camp that comes with the science and religion debate is absolutely false statements that get said over and over again. I hope these statements are based on a misunderstanding (or ignorance) of the science, and not on deliberate deceptive grounds.
Overall, I think the evidence for the earth being much older than 6,000-10,000 years is conclusive. I must state here, however, that this does not mean that I don’t believe the bible or that I think God was lying in the Bible or any other similar line of thought. I will explain what I think to be the solution to the conflict/tension towards the end of this series. I think there are better answers than denying the evidence or rejecting reason, but these answers are harder and take more effort. But we should know that if it was easy, it probably wouldn’t be worth it. I think it’s time we face these questions and evidence head-on, and develop a more robust theology that is able to stand times of great trial. It’s not like God is surprised that we are finding all these pieces of evidence- he created them! It has been said that God authored two books, scripture and nature. It is when we attempt to understand both books that we get closer to the truth. I hope you are enjoying our walk through the discussion between science and religion, and are considering the evidence. The age of the earth has historically been easier to swallow than our next topic, but I hope you consider the evidence in both cases fully before coming to a decision.
 See Young, D. & Stearley, R. The Bible, rocks and time: geological evidence for the Age of the Earth. (IVP Academic, 2008) p.132-134.
 This post does not contain the vast amount of evidence that has lead scientists to believe in an old earth/universe, it is only a beginning. It is not intended to be comprehensive.
 Whereas some anomalies might occur in tree rings, a trained eye can see the anomalies if they have multiple grown cycles in a year. The more likely discrepancy in tree rings and years, however, is that sometimes trees do not display a ring for a given year, which would make the estimate of age younger than it actually is- not older. See http://www.talkorigins.org/faqs/hovind/howgood-yea2.html#proof27 for further information.
 Becker, B, Palaeogeography, K.-B., Palaeoclimatology & Palaeoecology. The continental tree-ring record—absolute chronology, 14C calibration and climatic change at 11 ka. Palaeogeography (1993).
 Vasek, F. C. Creosote bush: long-lived clones in the Mojave Desert. American Journal of Botany 67, 246–255 (1980).
 May, M., Provance, M., Sanders, A., Ellstrand, N. & Ross-Ibarra, J. A Pleistocene Clone of Palmer’s Oak Persisting in Southern California. Plos One 4, e8346 (2009).
 Andersen, K. et al. The Greenland Ice Core Chronology 2005, 15–42ka. Part 1: constructing the time scale. Quaternary Sci Rev 25, 3246–3257 (2006).
 Meese et al. The Greenland Ice Sheet Project 2 depth‐age scale: Methods and results. J Geophys Res Oceans 1978 2012 102, 26411–26423 (1997).
 High-resolution record of Northern Hemisphere climate extending into the last interglacial period. Nature 431, (2004).
 Kitagawa, H. & Plicht, J. van der. Atmospheric radiocarbon calibration to 45,000 yr BP: Late Glacial fluctuations and cosmogenic isotope production. Science 279, 1187–1190 (1998). This study was actually able to calibrate the radiocarbon dating to 45,000 years ago by making some assumptions. I gave the more conservative number.
 Kashiwaya, K., Ryugo, M., Sakai, H. & Kawai, T. Long‐term climato‐limnological oscillation during the past 2.5 million years printed in Lake Baikal sediments. Geophys Res Lett 25, 659–662 (1998).
 Kashiwaya, K., Sakai, H., Ryugo, M., Horii, M. & Kawai, T. Long-term climato-limnological cycles found in a 3.5-million-year continental record. Journal of Paleolimnology 25, 271–278 (2001).
 Kashiwaya, K., Ochiai, S., Sakai, H. & Kawai, T. Orbit-related long-term climate cycles revealed in a 12-Myr continental record from Lake Baikal. Nature 410,35065057 (2001).
 See Young, D. & Stearley, R. The Bible, rocks and time: geological evidence for the Age of the Earth. (IVP Academic, 2008). p. 400-404.
 The word “theory” in no way implies that the process cannot be trusted. This theory is the mathematical basis for radioactive decay. To dismiss anything out right because it carries with it the term “theory” is to even reject the existence of gravity, which is itself a theory (one of which has been heavily modified over the years).
 For further reading, see hyperphysics overview: http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/raddat2.html#c1, the Wikipedia article, Young, D. & Stearley (IVP Academic, 2008). p. 388-442, Zumdahl, S. S. & Zumdahl, S. A. Chemistry. (Houghton Mifflin Company, 2003). p.840-873 (PDF here), and Weintraub, D. How old is the universe? (Princeton University Press, 2011). p.18-23.
 Zumdahl, S. S. & Zumdahl, S. A. (2003), p. 846-847.
 See Falk, D. Coming to peace with science: Bridging the worlds between faith and biology. 235 (IVP Academic, 2004), chapter 3.
 See Emery, G. T. Perturbation of nuclear decay rates. Annual Review of Nuclear Science 22, 165–202 (1972).
 Young, D. & Stearley (IVP Academic, 2008). p. 398.
 See Falk (2004), chapter 3, Giberson, K. & Collins, F. The language of science and faith: Straight answers to genuine questions. 251 (IVP Books, 2011), chapter 2.
 Reimer, P. IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0–50,000 Years cal BP. Radiocarbon 55, 1869–1887 (2013).
 See Young, D. & Stearley (IVP Academic, 2008). p. 407-414.
 Also see this article on radiometric dating in general: http://www.talkorigins.org/faqs/dalrymple/radiometric_dating.html
 Or to go talk to an actual geologist/paleontologist, or read any introductory textbook on the subject.
 Weintraub, D. How old is the universe? (Princeton University Press, 2011) p.22.
 See Weintraub, D. How old is the universe? (Princeton University Press, 2011).
 Ibid. p. 360-363.
 Ibid. p. 363.
 This philosophical point is actually referred to as “last Thursdayism”.
 See these resources for ample refutations of young-earth claims: http://www.talkorigins.org/faqs/dalrymple/creationist_age_earth.html#h32, http://www.talkorigins.org/faqs/hovind/howgood.html, http://www.oldearth.org/youngministry.htm