The embryonic Universe may have turned like a stately merry-go-round, completing one rotation every 13 billion years or so. This radical new idea may explain the curious relationship between the masses of stars and galaxies and their spin rates.
Astronomers believe the Universe has expanded since the big bang about 15 billion years ago. A problem with the big bang theory, however, is that it leads to the unrealistic idea that the Universe emerged from a "singularity"-a state of infinite density.
Cosmologists have come up with many more or less bizarre ways of evading the singularity, often by appealing to as-yet undiscovered laws of quantum gravity. Now Saulo Carneiro, a physicist at the Federal University of Bahia in Brazil, has come up with arguably the strangest yet: that the early Universe rotated.
The possibility of a rotating Universe has a distinguished pedigree: mathematician Kurt Gsdel dug the idea out of the equations for Einstein's general theory of relativity in 1949. Gsdel's Universe has similarities to the expanding model of the cosmos. Carneiro has now exploited these in a theory which says there was no big bang singularity, but that the early Universe had been rotating for an indefinitely long period.
This rotation could have suddenly changed into an expansion thanks to a "vacuum phase transition" involving the release of energy generated by quantum fluctuations, says Carneiro. Such phase transitions have become a standard part of conventional cosmological theory.
Carneiro has calculated that the early Universe would have had to complete one rotation every 13 billion years to fit in with estimates of the expansion rate of space. It would have stopped rotating and begun expanding around 11 billion years ago.
If his idea is right, conservation of angular momentum would ensure that evidence would be visible today. Carneiro suspects it is-in the form of a mysterious "law" discovered in the 1970s, when astronomers found that the angular momentum of a planet, star or galaxy is proportional to the square of its mass.
Why this should be has been unclear. But in a paper submitted to Classical and Quantum Gravity, Carneiro shows that the rotating Universe would give objects some rotation in the expanding phase. He calculates that it should leave each with an angular momentum proportional to its mass raised to the power 1.7, close to the observed value.
Astronomer Paul Wesson of the University of Waterloo in Ontario, Canada, says Carneiro's theory is interesting. But he can't see how the angular momentum would be inherited from the early phase: "I am not saying he is wrong, but it seems to me that there must be a simpler explanation."
Carneiro says his aim is not to overturn conventional cosmology: "The most important aspect of the paper is just that it calls attention to the possibility of alternative scenarios for the evolution of the Universe."
Author: Robert Matthews
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