In December of 2010, Dr. Amir Hajian from the Canadian Institute for Theoretical Astrophysics (CITA), produced a well-received study that refuted a claim made by Sir Roger Penrose and his colleague Vahe Gurzadyuan (PG) that the Universe is cyclical. PG reported the detection of low variance circles in the Cosmic Microwave Background (CMB) sky, which they believed, supported the Conformal Cyclic Cosmology (CCC) theory. Soon after their report was made public, Hajian published a study that clearly ruled out this theory.
Supporters of CCC believe the Universe is cyclical. It moves through cycles that last an extremely long time. At the end of a cycle the Universe undergoes a transformation that eventually leads to a new Big Bang, and a new Universe. PG claimed they had discovered anomalous low variance circles in the CMB sky, which they believed were left over from a previous Universe and further supported the theory that the Universe is cyclical.
For the greater Astrophysics community, including Dr. Hajian, the claim posed significant questions and concerns related to Inflationary Theory and to our understanding of the history of the Universe. Inflationary cosmology explains a number of questions surrounding the Big Bang. It posits that the Universe underwent a period of rapid expansion that allowed it to reach its current size. During this expansion the Universe became homogeneous and uniform, since any clumped matter was smoothed out as the Universe stretched.
PG’s claim did not hold up against the Inflationary theory and was quickly ruled out. If another Universe had previously existed, undergoing rapid expansion and subsequent uniformity, inflation of the current Universe would not have been necessary. When PG’s report was published Hajian had additional questions, such as: what would drive the Universe to transform and undergo another Big Bang?
In order to further understand the significance of these low variance circles, Dr. Hajian investigated the claim. He repeated PG’s study by comparing the observed CMB maps of the Universe to a series of simulations.
During the investigation Hajian detected the circles reported by PG, who had initially discover the rings using data collected from the Wilkinson Microwave Anisotropy Probe (WMAP).
Hajian, using realistic Monte Carlo simulations of the CMB sky, tested the statistical significance of the circles. In total he conducted 200 simulations. His study found the same low variance circles reported by PG, but when comparing the data and the Monte Carlo simulations, Hajian found nothing anomalous about the circles. The circles were “perfectly normal,” and could occur “in a universe consistent with inflationary theory.”
Hajian’s work is also supported by the results of two independent studies led respectively by Hans Kristian Eriksen and Ingunn Wehus from the University of Oslo, and Douglas Scott, Jim Zibin, and Adam Moss from the University of British Columbia. Each separate analyses arrived at the same conclusion – there was nothing odd about the circles in the observed maps of the Universe.
PG’s theory had been interesting and potentially ground-breaking, but Hajian’s work, along with other independent studies, highlighted that a more analytical understanding of PG’s model would be necessary if it wished to answer questions like: If the circles did belong to a previous Universe, how did they survive? And how do the claims account for the inflationary theory?
In a statement made to National Geographic, Hajian stated that “[i]n principle, it [PG theory] works on paper, but it’s still missing details and quantitative predictions” – some of which have already been answered by Inflationary Cosmology.
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Additional Sources and references:
Bangs big and small in cosmic origins debate
Space Circles Are Proof of a Pre-Big Bang Universe?
No evidence of time before Big Bang
Going round in circles