INTRO BY DEB: While much of our work at BioLogos is about presenting the case for evolutionary creation, we also take the time to analyze scientific proposals made by Christians who oppose evolution and an ancient universe. Today we continue a blog series focusing on a proposal from young-earth creationist scientist Jason Lisle to explain how distant starlight could have reached Earth if the universe were created roughly 6,000 years ago. Our guide through the topic is Casper Hesp, a graduate student in astrophysics and a gifted science writer. This series is intended for readers without any background in astronomy who want to learn more about God’s creation and how to think carefully about issues of science and faith.
For any newcomers to this series, I will first recap the conclusions of our previous posts. Distant starlight poses a challenge for young-earth creationism, because if the Earth is only six thousand years old, it’s difficult to explain how we are able to see stars that are millions of light years away. Astrophysicist Jason Lisle (a young-earth creationist) acknowledged the seriousness of this problem and has put forward a novel solution called the Anisotropic Synchrony Convention model (ASC model). This proposal involves a way of synchronizing clocks such that the speed of light is infinite towards every observer (see also our first installment for more details). As such, it is aimed at explaining how light could have reached Earth instantaneously during a six-day Creation event. As we have seen, this proposal suffers from some serious issues, both in theory and in practice.
In the second and third posts of this series, we discussed serious theoretical problems which are specific to the ASC model. Most notably, this model does not respect the physical limitations of light, it actually stretches Creation across billions of years, and it places the Earth at the center of the universe. After the theoretical issues, we went on to discuss observations which are problematic both for young-universe models in general and for the ASC model in particular. In the fourth post, for example, we looked at relativistic jets which can stretch 1,000,000 light years across the sky. The fifth post focused on how the galaxies in the universe are arranged in a way which appears to record billions of years of cosmic history. Young-universe models require the assumption that God created these phenomena with the mere illusion of event history. Today, we will discuss an observation which is presumably the most problematic of all. It concerns the Cosmic Microwave Background (CMB), low energy radiation which is literally present everywhere.
Introducing the Cosmic Microwave Background
Our universe is literally bathing in light, what scientists call the Cosmic Microwave Background (CMB). These light rays (photons) are so low in energy that they are invisible to the naked eye. To get an idea of how numerous they are, consider that every cubic centimeter is filled with about 400 of them. And every single second, as many as 20 trillion of these photons pass through the tip of your finger alone. The word microwave refers to the typical wavelength of this light (~2 mm). Its intensity curve across wavelengths follows a very distinctive shape (see the image below).
The CMB was discovered accidentally by radio astronomers Penzias and Wilson in 1965. They were trying to measure radio signals bouncing off of weather balloons. However, their measurements were disturbed by background noise which appeared to be coming from all directions. After going over their equipment many times, they excluded the possibility of any technical faults. It puzzled them greatly. Then, by mere chance, Penzias got to know that a group of astrophysicists over at Princeton had been making preparations to look for cosmic radiation as a remnant of the Big Bang. This specific theoretical prediction concerning the “afterglow” of the Big Bang had already been made 17 years earlier, in the year 1948.
It was at this point that Penzias and Wilson started to come to terms with the significance of their discovery. Their observations were within the exact predicted range aimed for by the Princeton astrophysicists (more about that below). To compare the explanatory power of the young-universe paradigm with that of “mainstream” modern cosmology, we will first look at the place of the CMB in a young universe. It appears the CMB cannot be accounted for in way that leaves young-universe models unscathed.
The (Lack of) Place for the CMB in a Young Universe
How might a young-universe model, such as the ASC model, deal with omnipresent radiation coming from all directions? This is a tough job, given the size of the observable universe (billions of light years) and a time restriction of about 10,000 years. In fact, no one has managed (or attempted) to give a physical description which might explain all the features of the CMB in a young universe.
Of course, a young-universe model could simply include a clause saying that the universe was initially created already filled with these light rays. A young-universe proponent might argue that this feature could be an integral part of creating a fully mature universe. Unfortunately, that assertion would still leave all those light rays without any physical source. All of the trillions of CMB light particles that are passing through us every second would have been created already “on their way” towards us. This argument is essentially saying that God created light in transit (with only an illusory connection to a physical cause). However, that same argument has been rejected completely by young-earth ministries such as Creation Ministries International. They have generally argued it would render Creation unintelligible. The rejection of this idea led to the necessity of new solutions to the distant starlight problem, which motivated Lisle to construct his ASC model. After investing so much effort in circumventing the light-en-route issue, it would be disconcerting if one were to reintroduce it by filling the universe with sourceless radiation. This point cannot be overemphasized.
Is there a more insightful way to interpret the CMB? Yes there is. In fact, as described above, Big Bang theorists predicted the existence and exact features of the CMB almost two decades before it was first discovered.
Resolving a dispute of cosmic proportions
The famous Soviet physicist Lev Landau (1908-1968) once said, “Cosmologists are often in error, but never in doubt.” It’s understandable that statements such as these give people the impression that cosmology is more like a belief system than an actual field of scientific inquiry. There were times when things were not as clear-cut as they are today. During the first half of the 20th century, cosmologists were roughly divided into two camps. Those of one camp (including big names such as Albert Einstein) subscribed to Steady State Theory, which involves an eternal universe without beginning or end. The other camp considered the notion of an expanding universe to be more convincing. To decide between these two, theorists have long determined their most important observational differences. Every one of these tests has favored the Big Bang model over alternatives. Of these, we only discuss the CMB today.
Young-earth creationists often claim that cosmology is more like a belief system than like a science. However, that neglects the fact that serious advancements in both theory and technology have been made after Landau’s time. Over the last 50 years, modern cosmology has earned its place among the sciences through rigorous empirical research. As I said in the previous post, the amazing (though not perfect) fit of the current cosmological standard model (Lambda-CDM) is one of the greatest achievements of modern science. In fact, the 2011 Nobel Prize in Physics was awarded to two teams of astronomers whose work accurately established the parameters of the current cosmological standard model (Big Bang). Nevertheless, the myth that cosmology is more like a religion than like a science is still being perpetuated in young-earth circles. This is unfortunate and completely dismisses the scientific work of cosmologists.The prediction of the CMB and its precise properties is an excellent illustration of how the field of cosmology has become the empirical science it is today.
The CMB as a baby picture of the universe
In 1948, the Big Bang model led to the prediction of the CMB by cosmologists. They reasoned that if the cosmos is expanding, there must have been an era in the past when it was too dense for light to travel freely. All matter was so hot and densely packed that protons and electrons were unable to form stable hydrogen atoms. These free charges were constantly interacting with the available light rays. Because of this constant interaction, the light was in balance with the energy of the hot material which filled our baby universe. As the universe kept expanding further, a time came (~300,000 years after the singularity) when the universe was cold enough for protons and electrons to combine and form neutral hydrogen atoms. From that point on, the available light rays could finally start traveling without scattering off free charges all the time. The intense flash of light which was released at that point in cosmic history reflected the properties of the universe back then, extremely hot and almost uniform. Envision this as a baby picture of the universe. The nicest part is that we know when the picture was “taken” because we know at which temperature protons and electrons become able to form stable hydrogen atoms (at ~3000 degrees Kelvin).
Now, over 13 billion years later, the expansion of the universe has stretched out the baby picture by a factor of 1000. This stretching has reduced the temperature by the same factor (~3 degrees Kelvin, close to the temperature predicted in 1948), but all its other properties are still the same. Around 1900, the great physicist Max Planck (1858 - 1947) developed an equation which later turned out to be perfectly applicable to the early universe. Planck’s law describes what light would be radiated by a “perfect emitter”, a source which can be completely described in terms of its temperature. Somewhat counterintuitively, physicists call such a source a “black body”. An old-fashioned light bulb would be an everyday example that approximates a black body. Stars provide a better approximation of the black body spectrum, although still relatively rough. It turns out that the CMB is the most ideal approximation to a perfect black body ever observed in nature. Below is a plot of the CMB light spectrum, comparing the theoretical black body to the actual observation. Actually the main plot includes error bars, but they are so small that they are invisible! I’ve included a double zoomed-in version to give you an idea of how ridiculously small the errors are.
The “brightness” (actually flux density in MJy per steradian) of the CMB plotted as a function of wavelength (in cm). Image made by me using data obtained from: http://lambda.gsfc.nasa.gov/product/cobe/firas_monopole_get.cfm
Pebbles in a pond: ripples in the CMB
We’ve just seen how the Big Bang model straightforwardly provided the exact shape and temperature of the CMB, to extraordinary precision. If you consider that to be amazing, then brace yourself, because there’s more. Besides the general shape of the CMB which is the same in all directions, it also has extremely small fluctuations in temperature. This was first measured in 1992 by the COBE project for which the 2006 Nobel Prize in Physics was awarded (see the main image). In some directions, the CMB is just a tiny bit hotter than others (the difference is about 0.0005 degrees Kelvin). Those small differences in density have been interpreted as the earliest “seeds” from which all the galaxies we see in the universe today formed. With a specific set of parameters for a cosmological model, specific predictions can be made concerning the distance between these seeds (measured in degrees on the sky). One analogy that is often used is that of a small pond in which many small pebbles are thrown. If we understand how the ripples travel and interact, we can predict the typical distance between the peaks on the water surface. For the CMB, this theoretical analysis results in a very precise prediction of the typical angular separation of the hot “seeds”. To give you a taste for the specificity of this analysis, see below for a plot of the theoretical prediction (green line) compared to the data points (blue points with error bars) gathered by the recent Planck telescope. Don’t break your head on the particular units, as it’s more meant for illustrative purposes.
The power in μK2 versus the angle in degrees. This plot indicates that the strongest “ripples” in the CMB are between 0.5 and 1 degree in size on the sky. Plotting done by me, using data from ESA/Planck, 2015 Cosmology products of the Planck Legacy Archive.
All of this work was effectively done using that single baby picture of the universe, the CMB. As a final step, we can link it back to what the universe looks like today. The size of the separation between the “seeds” in the CMB can be extrapolated to modern times by taking into account the cosmological expansion. The resulting scale of separation has been shown to correspond with typical present-day distances between galaxy clusters, providing further confirmation. It all connects. The current cosmological standard model combines these and many other findings in coherent ways. Despite having its own shortcomings, this level of elegance is currently surpassing all alternative models by far. There is currently no alternative in sight that might have the potential to integrate all the available findings. This is why most modern-day cosmologists aren’t constantly aiming to overthrow the whole paradigm. Instead, they’re working with the best we have.
The universe has a belly button
At the beginning of this post, we discussed how young-universe models such as Lisle’s ASC model have a tough job in explaining the CMB. One way or another, those models would require postulating the existence and properties of the CMB without any physical explanation. If one would posit that the CMB was “included” in the initial act of creation, this would revive the idea of light being created in transit (without a physical source). That is precisely the premise which Lisle aimed to avoid by constructing his ASC model. He argued that God would be a deceiver if he would create light that gives us the illusion of having been emitted by a source.
In the second part of this post, we have seen that the CMB has, in every way imaginable, the appearance of being a picture of the early universe. Both its overall shape and temperature, as well as its minuscule fluctuations correspond exactly with the predictions of the current Big Bang model. In a way, one could compare the CMB of the universe with the belly button of a human being. It’s a sign of your birth that you always carry with you. The CMB signifies the birth of the universe. Young-universe models either have to argue convincingly against this conclusion or to draw upon the Omphalos hypothesis. As we finish this empirical journey, it should have become abundantly clear that framing cosmology as a belief system, rather than a rigorous science, is a gross mistake. Frankly speaking, that is a myth perpetuated by those who disagree with the conclusions of mainstream cosmology. It completely defies the recent history of this scientific field, which happens to include the 2006 and 2011 Nobel Prizes in Physics.