Some theorists suggest that the universe grows and contracts endlessly in an effort to comprehend the nature of the cosmos. The cosmos should have no origin or finish, just endless cycles of expanding and contracting that reach into the past and the future indefinitely because this behavior is assumed to be everlasting.

It’s an enticing idea in part because it does away with the requirement for the singularity, which in other theories represents the “beginning of time.” However, a recent study by physicists Will Kinney and Nina Stein from the University of Buffalo reveals one weakness in cyclic or “bouncing” cosmologies.

According to the research, the most recent iteration of this theory—a cyclic model that addresses long-standing entropy-related concerns—increases the likelihood of a new issue (or rather, returns to an old one). Kinney and Stein draw the conclusion that the cyclic worlds described by this model must have a beginning.

According to Kinney, Ph.D., professor of physics in the UB College of Arts and Sciences, “People hypothesized bouncing universes to make the cosmos endless into the past, but what we show is that one of the newest varieties of these models doesn’t work.” “Even though the cosmos has cycles, it still needs to have a beginning in this new form of model that deals with entropy problems.”

The desire to know what came before is a natural human trait, according to Stein, a physics Ph.D. student at UB. “There are a lot of reasons to be curious about the early universe, but I think my favorite is the importance of study,” she adds. “People have long wanted to know their origins, and stories about creation and “in the beginning” have been told throughout human history and across all civilizations. The National Science Foundation-funded work was released in the Journal of Cosmology and Astroparticle Physics in June. “Cyclic cosmology and geodesic completeness” is the title of the essay.

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How did the universe start, if it had one?

An Infinity of Worlds, written by Kinney in 2022, chronicles the epic tale of cosmic inflation, a competing theory regarding the birth of the cosmos. According to this theory, the early universe consisted of a period of quick expansion from a singularity, followed by the superheated Big Bang, which created the primordial elements that later gave rise to galaxies, stars, and planets as well as the atoms that make up our bodies and all other living things.

One popular notion is cosmic inflation. However, it concentrates on what transpires during and after the period of fast increase. It doesn’t detail the circumstances surrounding the initial singularity or explain what came before it.

A really circular universe would avoid the following issues: It is unnecessary for the cosmos to have a beginning if it is always expanding and contracting. But as Kinney points out, these bouncing models also pose a number of unanswerable issues.

“Unfortunately, these cyclic theories have been known to be ineffective for almost a century because entropy, or disorder, accumulates in the cosmos through time and causes each cycle to differ from the one before it. It isn’t actually cyclical, “Kinney asserts. “A recent cyclic model proposes that the cosmos expands significantly with each cycle, reducing the entropy, in order to circumvent the problem of entropy build-up. The universe is stretched out to remove cosmic formations like black holes, which brings the universe back to its uniform state before the next bounce starts.”

But, he continues, “To cut a long story short, we demonstrated how the entropy problem has to be solved in order for the cosmos to exist. Our justification demonstrates in general that any cyclic model that reduces entropy through expansion must have a start.”

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According to Stein, “We want to know what there was before that. Scientists included. The concept that there was a period in time before which there was nothing, no time, troubles us. However, from what we can determine, there had to be a “first.” What came before that is a question for which there is no satisfactory response.”

Of course, there are more research problems, according to Kinney: “Our argument does not hold true for Roger Penrose’s cyclic model, in which the cosmos grows exponentially once every cycle. On that, we’re concentrating.”

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