Penrose’s idea of a conformal cyclic cosmology hypothesizes that our Universe arose from a pre-existing Universe that would leave imprints on our cosmos today. This is a fascinating and imaginative alternative to inflation, but the data doesn’t support it, despite Penrose’s dubious claims that it does. (SKYDIVEPHIL / YOUTUBE)

No, Roger Penrose, We See No Evidence Of A ‘Universe Before The Big Bang’

Despite the claims of one of Earth’s newest Nobel Laureates, the data doesn’t lie.

Ethan Siegel
Starts With A Bang!
9 min readOct 15, 2020

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One of the greatest scientific successes of the past century was the theory of the hot Big Bang: the idea that the Universe, as we observe it and exist within it today, emerged from a hotter, denser, more uniform past. Originally proposed as a serious alternative to some of the more mainstream explanations for the expanding Universe, it was shockingly confirmed in the mid-1960s with the discovery of the “primeval fireball” that remained from that early, hot-and-dense state: today known as the Cosmic Microwave Background.

For more than 50 years, the Big Bang has reigned supreme as the theory describing our cosmic origins, with an early, inflationary period preceding it and setting it up. Both cosmic inflation and the Big Bang have been continually challenged by astronomers and astrophysicists, but the alternatives have fallen away each time that new, critical observations have come in. Even 2020 Nobel Laureate Roger Penrose’s attempted alternative, Conformal Cyclic Cosmology, cannot match the inflationary Big Bang’s successes. Contrary to recent headlines and Penrose’s assertions, there is no evidence of “a Universe before the Big Bang.”

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Ethan Siegel
Starts With A Bang!

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.