Our current scientific understanding places the age of the Universe since the Big Bang at 13.8 billion years, with a precision of about 1%. In addition, scientists can date the age of our Solar System and Earth to about 4.5 billion years. In this series of blog posts, we review the scientific data that underpins these conclusions.
However, there are small numbers of scientists who claim that both the Universe and the Earth are in fact more like 6,000 years old. As we point out, those numbers are based upon an insistence that various numbers and genealogies found in the Bible are literally true. These “Young Earth Creationists” further claim that their conclusions are supported by objective scientific assessment.
In this four-part series we summarize the extensive data from a number of independent sources that lead mainstream scientists to converge on the ages of the Universe and the Solar System. Then we contrast this with arguments by Young Earth Creationists. We go into considerable detail about several YEC “theories;” even though these theories are quite arbitrary and internally contradictory, we give them a thorough review to expose their flaws. Furthermore, we provide links to articles and data sets that can be accessed by those who wish to follow these issues in more detail.
Here is a ‘road-map’ to the organization of our series. In part I, section 1, we summarize our current understanding of the origin and evolution of the Universe since the Big Bang. Some major milestones in the Big Bang Scenario are summarized in Fig. 1.1. This is contrasted with the historical timeline advocated by Young Earth Creationists, given in Fig. 1.2.
In Part I, section 2 we summarize different methods that are used to determine the age of the Earth. The first method is radiometric dating, a technique that utilizes the fact that certain isotopes are unstable. They undergo radioactive decay leading to known isotopes of different elements. Once one knows the “half-life” of the radioactive decay, one can determine the age of the substance by comparing the amounts of the original “parent” isotope and the “daughter” product of the decay.
A second independent method of dating is the analysis of fossils embedded in rock strata. Not only does this technique provide us with estimates of the age of the Earth, but in addition it allows us to construct a detailed geological history of the Earth.
A third method, analysis of ice cores, does not allow us to go back as far as the Earth’s origin. However, ice cores from Greenland or Antarctica provide year-to-year deposits, in direct analogy to annual information from tree rings. Currently, these ice core samples can go back as far as 800,000 years. The existence of such ice cores provides a very strong counter-example to theories that claim the Earth is about 6,000 years old; it is also extremely difficult to square the existence of such ice cores with theories that posit a world-wide flood within the past 6,000 years!
In Part II (section 3) of this series we summarize methods for determining the age of the Universe, and we outline the Big Bang Scenario (BBS), our current model of the origin and evolution of the Universe. In this section we review methods for determining the distance of objects in the Universe. The experimentally determined Hubble Constant shows us that the Universe is expanding, and allows us to calculate the rate of expansion of the Universe. Discovery of the Cosmic Microwave Background (CMB) radiation, and measurements of fluctuations in the CMB, have revolutionized the precision with which BBS features can be measured and tested.
Part III (section 4) reviews five different pseudoscientific attempts to reconcile existing scientific data with an extremely short (~ 6,000 year) lifetime for both the Universe and the Earth. The first of these is “tired light,” the notion that light loses energy as it travels through the cosmos to Earth. The second pseudo-theory invokes the idea that the speed of light has varied enormously over time. A third effort attempts to place the Earth at the center of the Universe and to construct a cosmology based on this notion. A fourth ‘theory’ assumes that rates of radioactive decay were enormously accelerated during the Great Flood or other biblical “miracles.” And a fifth attempt assumes that the geologic strata and fossil evidence found throughout the world were the result of recent occurrences associated with Flood geology.
In every case we point out the serious disagreement of these theories with experimental data. In some cases the central pseudo-scientific notion has no basis in physical theory. In other cases notions that explain one set of data disagree completely with other evidence. We attempt to point out the contradictions in these ideas.
Part IV contains sections 5 and 6. In section 5 we review attempts by creationists to criticize the successes of the Big Bang Scenario (BBS). The first is the false claim that there have been no successful predictions from the BBS that have been subsequently validated by experiment. A second false claim is that the BBS contains so many variable parameters that it could agree with any experimental data. And a third common creationist tactic is to seize on any small inconsistencies in the BBS, and assert that these represent fatal flaws in the BBS. Creationist critics often rely on outlier data sets or inconclusive measurements to make these claims.
In section 6 we point out that creationist “science” is unfalsifiable, and thus fails a crucial requirement for a valid scientific theory.
Science tells us that our Universe has evolved from an extremely compact beginning as a dense and ultra-hot assembly of matter and radiation that expanded and cooled rapidly since its beginning. Fred Hoyle, a theoretical astrophysicist who believed strongly that the Universe had no beginning and would have no end, sardonically coined the term “Big Bang” to describe the alleged beginning in which energy was suddenly converted to matter and radiation. The cosmology based on the concept of a Big Bang, however, has had enormous and widespread successes in accounting for, and in predicting, astronomical observations of various types. From these accounts, scientists have determined the age of our Universe to be 13.8 billion years, with an uncertainty less than 1%.
The Judeo-Christian Bible agrees that the Universe had a well-defined beginning. But those who insist on a literal reading of the Bible count the generations of humans to determine an age of around 6000 years. In contrast, geological estimates of the age of the Earth and our Solar System – using techniques completely independent of those used to deduce the age of the Universe – place that age at 4.5 billion years.
How can one justify the fundamentalist religious answer of 6000 years in the face of these enormous discrepancies with scientific observation and modeling? Many people simply accept the biblical answer on faith. Some scoff at the idea behind Lawrence Krauss’ unfortunate labeling of the Big Bang as getting “something from nothing,” misunderstanding that Krauss’ “nothing” refers to a physical vacuum that can carry huge amounts of energy. But young Earth creationists go further: they seek scientific approval and aim to teach their beliefs as science to young students. They therefore insist that the science behind both the geological dating of Earth and Big Bang cosmology must be completely rejected, to be replaced by pseudoscience invented to justify the biblical account after the fact. It is that organized science denial that we will deal with in this post.
How do we justify labeling one approach as science and the other as pseudoscience? As in other posts on this site, we identify the scientific approach by its standard methodology: making reproducible observations; building models and eventually theories to correlate various observations; testing predictions of those models with subsequent experiments; refining the models; and finally arriving at answers that could not have been known a priori to basic questions. In contrast, the pseudoscientific approach declares the answer to be well known at the start, and accepts only that evidence – whether or not it can withstand scientific scrutiny and be replicated by independent observers – that is judged compatible with the predetermined answer. This distinction was emphasized, for example (see quotation at the bottom of this web page), by Judge William Overton in his 1982 court ruling against the teaching of “creation science” as science in Arkansas public schools.
In this post, we will discuss the science behind the determinations of the age of the Universe and of the Earth. We will also expose the flaws in arguments presented by young Earth creationists to reject that science and instead to accept “magical” scientific explanations that rely on abrupt supernatural changes to the laws of nature. Young Earth creationists also, of course, reject the concept of macroevolution of the species, but the extensive science concerning that case will be treated in a later post on this site.
The vast differences between the cosmological and fundamentalist treatments of the Universe are further illustrated by contrasting Fig. 1.1 (the standard cosmological timeline of our Universe) with Fig. 1.2 (the biblical timeline). Of particular note in Fig. 1.1 are the incredibly rapid developments leading to formation of the first nuclei within several minutes after the Big Bang, followed by the gradual formation of galaxies and stars only billions of years later, and the appearance of the first life forms on Earth about ten billion years after the Big Bang. There is an enormous amount of science that informs this timeline, some of which will be discussed here in following sections. In the literal biblical account of Fig. 1.2, the heavens, the Earth, humans and all other life forms on Earth appeared within the first six 24-hour days of supernatural Creation. In creationist pseudoscience, the Great Flood that occurred some 1650 years later also plays a crucial role, as we shall see.
Figure 1.1. A schematic timeline for the evolution of the expanding, cooling Universe in Big Bang cosmology, indicating various critical stages in the development. Figure credit: E.P.S. Shellard, University of Cambridge.
The very well tested Theory of General Relativity, and the finite speed limit (constant speed of light) for all matter and radiation moving through space. Although modern cosmological analyses are based on General Relativity, we will sometimes use consistent classical physics arguments in this post to simplify the explanations we offer.
Figure 1.2. Biblical timeline for the six days of creation (above, from https://answersingenesis.org/big-bang/does-the-big-bang-fit-with-the-bible/) and for the generations of man described in Genesis (below, from http://www.bible.ca). Young Earth creationists insist that days described in the Bible (including the first three days, before the sun appeared) are 24-hour periods, not the longer periods suggested by some who interpret the Bible less literally, and that early men lived for nearly a thousand 365-day years.
In attempting to come up with pseudoscientific explanations for all the measurements that support the timeline of Fig. 1.1 – in other words, explanations for how nearly 14 billion years of Universe evolution can have been accomplished in six 24-hour days – young Earth creationists have to overthrow much of what we know about physics, astronomy, geology and biology. They must assume that the speed of light and the lifetimes of various radioactive isotopes changed radically and abruptly during Earth’s early years. They have to discredit the theory of evolution and assume that humans coexisted with dinosaurs and earlier species, negating fossil evidence to the contrary. They have to produce alternative explanations from a chronological buildup to account for observed strata in geologic formations like the Grand Canyon and in ice cores drilled from the Antarctic or Greenland. They have to come up with explanations for why human life expectancy in the early years would have exceeded current life expectancy by an order of magnitude, despite the great advances in medicine and diet (not to mention evolution) that have occurred since.
The biblical fundamentalists’ rejection of science embodied in this belief extends, in many cases, to a rejection of any science that yields “inconvenient” results, such as that backing up climate change (Fig. 1.3) or evolution (Fig. 1.4). Figure 1.3 shows the results of a recent multi-faceted analysis (Shao 2016) of an extensive American National Election Studies survey that performed in-depth interviews with nearly 6000 U.S. respondents both before and after the November 2012 election. The analysis allows detailed modeling of the effects that political, religious, ethnic and socio-economic factors, in addition to recent local weather trends, have on people’s perceptions of climate science. Controlling for all other factors, one of the strongest correlations found in this study is that in Fig. 1.3 between evangelical fundamentalism and belief in the existence, cause and impacts of global warming. The evangelical fundamentalism scale in Fig. 1.3 is based on respondents’ answers to survey questions regarding how literally they take the Bible as the word of God, whether or not they have personally experienced a religious rebirth, and their attitudes toward Christian fundamentalism. The results demonstrate that the stronger the belief in evangelical fundamentalism, the less likely the respondent is to accept the existence, primary human causes or predominantly negative impacts of global warming.
Figure 1.3. Analysis by Shao (2016) of an extensive survey correlating acceptance of climate science with adherence to evangelical fundamentalism, among many other factors. The frames represent respondents’ answers regarding (a) acceptance of rising global temperatures, (b) attribution of causes of global warming, and (c) evaluation of the future impacts of global warming. Identification with evangelical fundamentalism ranges from very weak (-2 on horizontal scale) to very strong (+2).
This rejection of science by religious fundamentalists is more prevalent in the U.S. than in almost any other western country (see Fig. 1.4), and it threatens formulation of sensible governing policies.
Figure 1.4. Survey responses in many western countries to the truth of evolution of the species. Only 40% of U.S. respondents accept this truth, the second lowest fraction among all countries surveyed. The figure is reproduced from New Scientist, Vol. 198, No. 2652, April 19, 2008.
2. How is the Age of the Earth Determined?
Many ancient materials can be dated by taking advantage of the natural radioactive decay of certain isotopes, creating daughter isotopes that would not have been naturally present in the material at its creation. Such radioactive decay is illustrated for the case of carbon-14 in Fig. 2.1. Carbon-14, while it occurs naturally, is unstable to beta-decay to the daughter isotope nitrogen-14, by converting one of the eight neutrons in the carbon-14 nucleus to a proton, an electron (the beta particle) and an antineutrino. The decay is a random process, with each carbon-14 nucleus in a sample having identical probability to decay in any given second of its lifetime. The decay is characterized by a very well measured half-life of 5730 years. As indicated in Fig. 2.1(b), half of the originally present carbon-14 nuclei will still be present after one half-life, with the other half having been converted to nitrogen-14. After a second half-life, half of the remaining carbon-14 nuclei will have been converted, and so forth. By measuring the ratio of nitrogen-14 to carbon-14 nuclei in the material at any moment, one can determine the total time over which the decay has been proceeding.
Figure 2.1. (a) Schematic illustration of the nuclear and atomic composition of the carbon isotopes carbon-12, 13 and 14, and of the carbon-14 stable daughter nucleus nitrogen-14. (b) Illustration of the characteristic exponential decay curve of a radioactive isotope.
Such radiometric dating is the central method by which the absolute age of rocks and fossils has been determined on Earth, in lunar samples and in meteorites that have struck Earth. If carbon-14 were the only long-lived radioactive isotope available for such dating, it would be difficult to determine any ages beyond about 30,000 years, because by then most of the originally present carbon-14 nuclei would have decayed away. But in fact, there are several suitable radioactive isotopes spanning an enormous range in half-lives and thereby facilitating radiometric dating of materials up to billions of years. Figure 2.2 lists the isotopes most often used and the age ranges for which they are suitable. The overlap in age ranges accessible with various isotopes allows important cross-checks on age determinations for rocks and fossils. Despite claims to the contrary by some young Earth creationists (to be discussed in Sec. 4), there is no evidence that any radioactive decay lifetimes have changed significantly during the Earth’s existence.
Figure 2.2. The half-lives and useful age ranges for several radioactive isotopes that are used for radiometric dating of geological samples.
These radiometric techniques have by now been applied to hundreds of meteorites , which have the advantage, in comparison with Earth rocks, of having not suffered through the geological evolution of the Earth and its possible mixing and unmixing of various samples. The most precise age measurements that have been made extract the ratios of two lead isotopes (207 vs. 206) resulting from the radioactive decay chains starting from two different isotopes of uranium, with decay half-lives differing from one another by about a factor of six, as shown in Fig. 2.2. The abundance of these two lead isotopes is measured in comparison to that of other lead isotopes that do not result from radioactive decay, and the ratios are also compared to those in galena lead ores that are believed to represent the naturally occurring isotope ratios in the absence of any initial uranium. Furthermore, the isotope ratios are normally measured for several different mineral samples from the same meteorite, which may have started with quite different concentrations of uranium. The results from many meteorites fall within an age range from 4.53 to 4.58 billion years!
These lead isotope ratio measurements are confirmed, although typically with slightly worse precision, by radiometric dating based on different radioactive isotopes. The results suggest that the solar system must have started forming at least 4.56 billion years ago! Samples from the Moon returned from the Apollo space missions are also quite useful, as these have not been disturbed by eons of Earth plate tectonics or weathering, or material movement by living organisms. Radiometric dating of Moon samples has so far found a maximum age of around 4.51 billion years. The oldest Earth minerals analyzed to date were housed in small zircon crystals extracted from the Jack Hills of Western Australia, found by radiometric dating to be 4.40 billion years old. On the basis of all of these data, the best estimate for the age of the Earth is 4.54 billion years, with an uncertainty of 1%. That uncertainty encompasses a range of estimated time intervals from several million to a hundred million years for material to accrete to form Earth, after the birth of the solar system. In any case, it is not possible, absent magical thinking to be discussed in Sec. 4, to reconcile these radiometric dating measurements with a solar system and Earth that are only 6000 years old.
Figure 2.3. Sequentially deposited horizontal rock layers (strata) in the Grand Canyon.
When these radiometric techniques are combined with the analysis of fossils embedded in rock strata, the results provide a much more complete picture of the geological evolution of the Earth during its lifetime. The Grand Canyon in the western United States provides an excellent example of an ancient geological structure that displays clearly differentiated strata, as seen in Fig. 2.3. In analyzing such layers, geologists assume that they were initially deposited horizontally and sequentially, so that each layer is younger than those below it and older than those above. Occasionally such layers have been pushed up toward the vertical by subsequent tectonic plate movement or other geological shifts. But in any case, examining the rock and the fossils within each distinct layer provides a relative timeline for the geological and evolutionary history of Earth. The role of the fossils in such relative stratigraphic dating is illustrated in Fig. 2.4.
Figure 2.4. Schematic illustration of the stratigraphic analysis of fossil ages to aid in determining a relative timeline for depositing rock layers. The grey arrows in the right-hand illustration represent age ranges determined from worldwide radiometric dating on each given fossil species. When fossils with only slightly overlapping age ranges, such as the blue and red examples, fall within the same rock layer (such as the pink layer), the deposition of that layer is constrained to the overlap region between the two corresponding fossil arrows. Fossils that appear in deep layers but not in layers above represent species that became extinct before the deposition of the higher strata. © 2013 Nature Education. All rights reserved.
The absolute age of the rock and fossils relevant to different strata is determined by the sort of radiometric analysis described above, supplemented by other techniques that assess the accumulation of electrons released in radioactive decay over the years within imperfections in the crystal structure of minerals. Where multiple methods can be applied, the different techniques give consistent dating results. Some of the minerals analyzed within rock strata have an intrinsic magnetism that tends to preferentially align itself, like a compass needle, along the Earth’s overall magnetic field. By analyzing the preferential orientations of such magnetic materials in different strata, geologists have also revealed a series of historical reversals in the direction of Earth’s magnetic field, from pointing toward the north geographic pole to pointing toward the south, or vice-versa. Such reversals presumably reflect changes in convection currents within Earth’s core. When the radiometric, stratigraphic and geomagnetic data are combined, they provide a detailed geologic history of the Earth, reflected in the timeline shown in Fig. 2.5, stretching back over four billion years.
Figure 2.5. The standard geologic timeline of Earth, laying out the sequence of epochs and, where data are available, of Earth magnetic field reversals, deduced from the dating of very many rock and fossil samples worldwide. The record stretches backward some four billion years from the present. © 2009 The Geological Society of America.
It took hundreds of millions of years after Earth’s birth for the simplest life forms to emerge. The oldest dated fossils found in rocks at this point are of microbial mats discovered in 3.5 billion year old sandstone from Western Australia. Biogenic substances have also been reported in 3.7 billion year old graphite recovered from Western Greenland. Very recently, there has been a report of fossilized microorganisms discovered within 4.28 billion year old precipitates from hydrothermal vents in Quebec, Canada. The length of time it takes biomolecules to form from primitive organic materials is of great interest in formulating models of life’s origins, but in any case, the fossil samples again demonstrate that the Earth is far more ancient than a literal reading of the Bible would suggest.
There are also other, independent means for dating objects on Earth that do not stretch back in time to Earth’s beginnings, but nonetheless reveal that the age is far greater than 6000 years. An example that has become prominent in recent climate science experiments is provided by dating of ice cores drilled in the Antarctic or Greenland or Vostok. Such ice cores also display strata, as seen in Fig. 2.6. But in this case, each pair of darker and lighter strata reflects a single year’s snowfall, with the lighter snow of summer leading, after compaction into ice, to less optically dense layers with larger air bubbles. Hence, the age of ice cores can often be simply counted, as with tree rings. Such layer counting only works down to a certain maximum depth, below which one can no longer discern the bubbles. But that maximum depth already corresponds to an age of 55,000 years in the case of ice cores from Vostok, for example. At greater depths, one can still sometimes distinguish annual layers via seasonal variations in the accumulation of dust particles that make the ice cloudy, or one can use radiometric dating on trapped gases such as carbon dioxide. Using these techniques, ice cores have been successfully traced back for about 800,000 years.
Figure 2.6. A 19 cm long section taken from a depth of 1855 meters within an ice core drilled in Greenland. The section contains 11 annual layers revealed by illumination from below, with the lighter summer layers marked by arrows sandwiched between darker winter layers. Such layers can be individually counted to depths corresponding to ages of more than 50,000 years. Other techniques are used to date deeper ice. The figure is reproduced from here.