Are Spiral Galaxies Evidence Against an Old Universe?

The movie “Is Genesis History?” (IGH), which premiered earlier this year in theaters and has since made accessible through Netflix, is perhaps the most polished presentation of the scientific case for young-earth creationism ever created. The movie, which has been previously covered by BioLogos several times, features interviews with a number of credentialed young-earth scientists (all have PhDs in relevant fields, mostly from respected universities). But the movie is clearly aimed not at fellow scientists but non-scientists.

The problem is that non-scientists within and without the Church—no matter their perspective on origins—cannot fully evaluate the validity of a scientific argument without having extensive background knowledge of the subject matter. The next best option is to consult with people who have a decent overview of the field of research in question. Even experts need others to scrutinize their lines of reasoning (that’s why we need the peer-review process of academic journals). Given the reliance on expert witness in IGH, it is necessary to call in “witnesses” with a scientific background to reflect critically on this movie. BioLogos and friends have already published such responses from the perspectives of geology and paleontology. Given my background in astronomy, I will make a contribution by addressing one of the claims of Dr. Danny Faulkner (PhD in astrophysics).

There are certain rhetorical patterns that are recycled across the spectrum of topics in IGH and the young-earth movement in general. In this case, we will see a mixture of three such problems:

1. Selective presentation of information: cherry-picking, not mentioning details of crucial importance.
2. Reliance on negative logic: focusing on arguments against the consensus age of the universe (13.6 billion years), without presenting actual evidence for a timeline of 6,000-10,000 years. It is like claiming that I must currently be in Tokyo, by arguing that I am not in Amsterdam.
3. Disregarding recent progress: not mentioning the recent answers scientists have found to legitimate questions in the past, a variation of problem 1.

Here’s the full transcript of the exchange between the movie’s host and narrator, Del Tackett, and Danny Faulker, a young-earth creationist astronomer:

Del Tackett: “Are there things that you see that would point to a young universe?”

Danny Faulkner: “I think so. For instance […] the Andromeda galaxy we talked about is a spiral galaxy, [and] our own is, and the inside of the galaxies should spin faster than the outside of the galaxies, so after a few rotations you ought to have wound up or smeared out those spiral patterns, and they would have to disappear after a few rotations. Now most astronomers think that spiral galaxies are 10 billion years old, so why do we still see spiral patterns? You should not see those. And it’s been long recognized as a problem.

I can see how this argument speaks to the lay reader. The universe is full of galaxies, each containing billions of stars. Many of them have beautiful spiral arms, as illustrated in the main image. Faulkner’s argument suggests that one might expect these spiral arms to coil up around the center of their host galaxy over time. This is not an unprecedented claim. There was a time when astronomers were indeed divided over how these structures could remain stable for more than a hundred million years. However, this does not mean that the claim is without problems.

First, note that Faulkner did not inform the audience about this humongous time scale. It was never anywhere near 6,000-10,000 years. If the problem Faulkner is highlighting had not been since resolved, astronomers might have concluded that such spiral structures are indeed at most 100 million years old. However, it is a huge leap from “this specific structure in the universe is at most 100 million years old” to “the entire universe is most likely 6,000-10,000 years old”. The claim is a combination of problems 1 and 2 above. It omits the crucial piece of information of the 100-million-year time scale and relies on negative logic: 100 million years does not get us anywhere near 10,000 years.

Two years ago, I was quite surprised when I encountered people using galactic spiral arms to argue for a young earth. At the time, I had spent almost a full year in a research group on galactic dynamics. With my own eyes, I had seen computer simulations of galactic discs in which spiral arms formed by themselves and persisted for billions of years. Yet, somehow, IGH confronts the viewer with Faulkner, someone with a PhD in astrophysics, claiming that spiral arms are not stable enough for an ancient universe. The main problem is that Faulkner’s account of scientific research is outdated (problem 3 above). Recent simulations have shown that these spirals form naturally and easily remain stable over the course of billions of years. In fact, under the current cosmological standard model, spiral arms are not just plausible, they are necessarily present in an ancient universe. Faulkner is therefore seriously mistaken in his statement that spiral galaxies still present a problem for mainstream astronomy. On the contrary, it would be a problem if we did not observe these structures abundantly.

How exactly do galactic spiral arms remain stable over hundreds of millions of years, without getting all jumbled up? As it turns out, spiral arms are actually “density waves” of stars, comparable to traffic jams. Individual cars enter and leave a traffic jam continuously, but the location of the traffic jam itself can remain surprisingly stable. The same applies to galactic spiral arms: they remain stable, even when individual stars move in and out.

The formation and stability of galactic spiral arms is not only possible, but necessary under the current standard model of cosmology, called Lambda-CDM. In the simulations mentioned previously, astronomers found that both the formation and stability of spiral arms are neatly explained by dark matter. This is an amazing feat of the standard model, given that dark matter was introduced for completely different reasons.^[1] In cosmological simulations of the Big Bang, many clumps of dark matter of different sizes form (most lead to “dwarf galaxies”). Their gravitational attraction can disturb large galactic discs, introducing differences in density that eventually lead to spiral arms. We can again compare this picture to traffic jams, which can be quickly triggered by a disturbance (e.g., a closed lane after an accident). After the initial formation of spiral arms, the more diffuse dark matter helps to stabilize their shape. As such, the observed abundance of spiral galaxies actually supports the picture of the Big Bang instead of undermining it.

The current Big Bang model manages to capture the universe in amazing detail: from the ever-present bath of radiation (the Cosmic Microwave Background), to the distribution of galaxies, down to features of individual galaxies, like stellar streams and the spiral structures we discussed here. In contrast, Faulkner’s argument for a young universe, based on galactic spiral arms, is demonstrably incorrect and outdated. That is unfortunate, because IGH aims to convince the viewer that there is a scientifically robust case to be made for a young earth. Time and time again, taking a closer look at the claims made in this movie leads to disappointment.