Why Can't the Universe Be Cyclic? Part 1: The Lure of the Eternal Universe

A look at why a cyclic, eternally repeating universe is such an appealing idea, and why the first serious attempt to build one, Richard Tolman's 1930s model of endless big bangs and big crunches, collapsed under the weight of entropy. The science-journalism coverage adds useful context, while the strongest evidential footing still comes from the underlying data, papers or institutional documentation.

It is relevant because astronomy does not advance on single detections. The field builds confidence by accumulating independent observations across different wavelengths, instruments and epochs until isolated signals become defensible conclusions. What looks convincing in one dataset can dissolve when a second instrument looks at the same target, and what looks marginal can solidify when follow-up campaigns confirm the original reading. The current standard requires that a result survive this triangulation before the community treats it as settled. It has lots of drama, good action, a dying inflation field flooding the young cosmos with light and particles, and the grand central mystery of the singularity sitting right there. Sure, the next one might not come around for another 14 trillion years, but the point is that it comes around at all.

It was born, it has already sailed past its glory days, and from here on out there is nothing but expansion into the deepening cold of the vacuum. This linearity is a big part of what made the Big Bang so aggravating to so many people when it first arrived.

So it is no surprise that in the century or so since it was first scribbled down, people have kept trying to bend our cosmology back into a circle. The first person to really go for it was Richard Tolman, working all the way back in the 1930s, right as the standard Big Bang picture was itself just swimming into focus.

Tolman pictured a universe of big bangs followed by big crunches followed by more big bangs (nobody was using those names yet, but it's the same idea). No first one, no last one, just the eternal heartbeat of a universe that breathes in and breathes out.

What gives the story weight is not just the object itself, but the way the measurement trims the range of plausible physical explanations. Astronomy has accumulated enough cases to know that the most interesting results are rarely the ones that confirm expectations cleanly; they are the ones that confirm some expectations while complicating others, or that open a parameter space that previous instruments could not reach. The scientific community evaluates these contributions by asking whether the new data constrain a model in a way that older data could not, and whether those constraints survive systematic review.

Until, inevitably, you arrive at a first one. In a crunch, all of that entropy gets crushed back down into a tiny volume with absolutely nowhere to go.

Because this item comes through Universe Today as science journalism, it should be treated as contextual reporting rather than primary evidence. Good science reporting can identify why a result matters, connect it to the wider literature and make technical work readable, but the decisive evidence remains in the original paper, dataset, mission release or technical record. That distinction is especially important when a story is later repeated by aggregators, because repetition increases visibility, not evidential strength.

The next step is to see whether other instruments and other wavelengths tell the same story. Campaigns with JWST, the VLT, the forthcoming Extremely Large Telescopes and radio arrays will provide the spectral coverage and spatial resolution needed to move from detection to physical characterization. The timeline for that kind of confirmation is typically measured in years, not months, which is worth keeping in mind when reading the current result.

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