There's something exciting afoot in the world of cosmology. Last month, Roger Penrose at the University of Oxford and Vahe Gurzadyan at Yerevan State University in Armenia announced that they had found patterns of concentric circles in the cosmic microwave background, the echo of the Big Bang.
This, they say, is exactly what you'd expect if the universe were eternally cyclical. By that, they mean that each cycle ends with a big bang that starts the next cycle. In this model, the universe is a kind of cosmic Russian Doll, with all previous universes contained within the current one.
That's an extraordinary discovery: evidence of something that occurred before the (conventional) Big Bang.
Today, another group says they've found something else in the echo of the Big Bang. These guys start with a different model of the universe called eternal inflation. In this way of thinking, the universe we see is merely a bubble in a much larger cosmos. This cosmos is filled with other bubbles, all of which are other universes where the laws of physics may be dramatically different to ours.
These bubbles probably had a violent past, jostling together and leaving "cosmic bruises" where they touched. If so, these bruises ought to be visible today in the cosmic microwave background.
Now Stephen Feeney at University College London and a few pals say they've found tentative evidence of this bruising in the form of circular patterns in cosmic microwave background. In fact, they've found four bruises, implying that our universe must have smashed into other bubbles at least four times in the past.
Again, this is an extraordinary result: the first evidence of universes beyond our own.
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