In my previous article, I summarized how astrophysicist Ethan Siegel presented an argument against the universe having a beginning based on the cosmological model known as eternal chaotic inflation. I concluded by describing how Stephen Meyer dismantled Siegel’s argument in Return of the God Hypothesis.
Here I will address another desperate attempt to avoid a cosmic beginning, this one by astrophysicist Paul Sutter. He is a research professor at the Institute for Advanced Computational Science at Stony Brook University and the Flatiron Institute in New York City. He recently published at the website Live Science an article titled “What if the universe had no beginning?” Sutter argues that a cosmological model based on causal set theory demonstrates that the universe might not have had a beginning. His argument upon close inspection also collapses.
Causal Set Cosmology
Causal set cosmology (CSC) is founded on the application of causal set theory (CST) to unifying quantum mechanics with general relativity (aka quantum gravity). This approach postulates that space is not continuous, but it is composed of discrete granules with a size on the order of the Planck length (10-35 m). The spatial granules take the form of the elements in a causal set, and the relationships between the elements capture how space changes in discrete increments of time.
The causal set models the dynamics described by the mathematical relationships in Einstein’s field equations of general relativity in the quantum realm where general relativity breaks down. The causal-set framework has been employed by cosmologists in the context of universes emerging out of black holes. This context corresponds to a universe collapsing and then bouncing in a Big Bang event into a state of expansion.
Sutter references a preprint article employing CSC by physicists Bruno Valeixo Bento and Stav Zalel titled “If time had no beginning.” He summarizes their work as follows:
The paper examined “whether a beginning must exist in the causal set approach,” Bento said. “In the original causal set formulation and dynamics, classically speaking, a causal set grows from nothing into the universe we see today. In our work instead, there would be no Big Bang as a beginning, as the causal set would be infinite to the past, and so there’s always something before.”
…Their work implies that the universe may have had no beginning — that it has simply always existed. What we perceive as the Big Bang may have been just a particular moment in the evolution of this always-existing causal set, not a true beginning.
Confusing Imagination with Reality
Sutter asserts that Bento and Zalel’s article offers a credible response against the evidence for a cosmic beginning. Yet this claim is only based on what might be possible in the realm of the imagination. The referenced paper is a highly theoretical and entirely speculative cosmological model that is almost entirely divorced from physical reality. Sutter even acknowledges this point:
There’s still a lot of work to be done, however. It’s not clear yet if this no-beginning causal approach can allow for physical theories that we can work with to describe the complex evolution of the universe during the Big Bang.
His claiming that Bento and Zalel’s paper represents a credible refutation of a cosmic beginning is like a journalist interviewing a scientist who imagines a new possible rocket fuel and then claiming that the scientist demonstrated how NASA could establish permanent colonies on Pluto. Such sensationalist reporting is deeply irresponsible.
Oscillating Models and Entropy
Moreover, even if a mature version of CSC eventually described the Big Bang, it would not avoid a cosmic beginning. Proponents of CSC could assume an oscillating universe where Big Bang events correspond to a contraction stage transitioning according to causal-set dynamics to an expansion stage. In such a case, CSC is only needed to describe the bounces. Both the contractions and expansions would follow standard cosmological models for oscillating universes. Stephen Meyer explained in his book why an oscillating universe still requires an absolute beginning.
Specifically, Meyer summarized how cosmologist Alan Guth demonstrated that the oscillations could not continue indefinitely due to entropy:
Guth showed that, according to the second law, the entropy (or disorder) of the matter and energy in the universe would increase over time in each cycle. But such increases in entropy (or the disorderly distribution of mass-energy) would result in less energy available to do work in each cycle. That would cause progressively longer and longer cycles of expansion and contraction, since increasing inhomogeneities in the mass-energy density throughout space would decrease the efficiency of gravitational contraction. Yet if the duration of each cycle necessarily increases as the universe moves forward in time, then it follows that each cycle in the past would have been progressively shorter. Since the periods of each cycle cannot decrease indefinitely, the universe — even in an oscillating model — would have had to have a beginning.Return of the God Hypothesis, p. 105