Circular patterns within the cosmic microwave background suggest that space and time did not come into being at the Big Bang but that our universe in fact continually cycles through a series of “aeons”. That is the sensational claim being made by University of Oxford theoretical physicist Roger Penrose, who says that data collected by NASA’s WMAP satellite support his idea of “conformal cyclic cosmology”. This claim is bound to prove controversial, however, because it opposes the widely accepted inflationary model of cosmology.
Penrose takes issue with the inflationary picture (inflation after a big bang) and in particular believes it cannot account for the very low entropy state in which the universe was believed to have been born – an extremely high degree of order that made complex matter possible. He does not believe that space and time came into existence at the moment of the Big Bang but that the Big Bang was in fact just one in a series of many, with each big bang marking the start of a new “aeon” in the history of the universe.
Central to Penrose’s theory is the idea that in the very distant future the universe will in one sense become very similar to how it was at the Big Bang. He says that at these points the shape, or geometry, of the universe was and will be very smooth, in contrast to its current very jagged form. This continuity of shape, he maintains, will allow a transition from the end of the current aeon, when the universe will have expanded to become infinitely large, to the start of the next, when it once again becomes infinitesimally small and explodes outwards from the next big bang. Crucially, he says, the entropy at this transition stage will be extremely low, because black holes, which destroy all information that they suck in, evaporate as the universe expands and in so doing remove entropy from the universe.
Penrose now claims to have found evidence for this theory in the cosmic microwave background, the all-pervasive microwave radiation that was believed to have been created when the universe was just 300,000 years old and which tells us what conditions were like at that time. The evidence was obtained by Vahe Gurzadyan of the Yerevan Physics Institute in Armenia, who analysed seven years’ worth of microwave data from WMAP, as well as data from the BOOMERanG balloon experiment in Antarctica. Penrose and Gurzadyan say they have clearly identified concentric circles within the data – regions in the microwave sky in which the range of the radiation’s temperature is markedly smaller than elsewhere.
The circles, they say, are the marks left in our aeon by the spherical ripples of gravitational waves that were generated when black holes collided in the previous aeon. And they say that these circles pose a problem for inflationary theory because this theory says that the distribution of temperature variations across the sky should be Gaussian, or random, rather than having discernable structures within it.