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Μοντέλα του σύμπαντος του Friedman. Το καθένα από αυτά έχει ως αρχή τη Μεγάλη Έκρηξη
Two physicists are trying to revive one of the great debates of twentieth-century science, arguing that the Big Bang may never have happened. Their work presents a radically different vision of the universe from the one cosmologists now work with.
The term Big Bang was created by astrophysicist Fred Hoyle as a way to mock the theory. Hoyle thought of the universe as like an endlessly flowing river, saying “Things are they way they are, because they were the way they were.” However, the weight of evidence—particularly the discovery of the cosmic background radiation—led the scientific community to overwhelmingly favor the idea that the universe came into being from a single, infinitely dense point.
Nevertheless, the problem of what, if anything, came before the Big Bang has continued to trouble many scientists, along with questions about how it actually occurred.
"The Big Bang singularity is the most serious problem of general relativity because the laws of physics appear to break down there," says Dr. Ahmed Farag Ali of Benha University, Egypt. In collaboration with Professor Saurya Das of the University of Lethbridge, Canada, Ali has created a series of equations that describe a universe much like Hoyle's; one without a beginning or end. Part of their work has been published in Physics Letters B, while a follow-up paper by Das and Rajat Bhaduri of Manchester University, Canada, is awaiting publication.
Ali and Das are keen to point out that they were not seeking a preordained outcome, or trying to adjust their equations to remove the need for the Big Bang. Instead they sought to unite the work of David Bohm and Amal Kumar Raychaudhuri, connecting quantum mechanics with general relativity. They found that when using Bohm's work to make quantum corrections to Raychaudhuri's equation on the formation of singularities, they described a universe that was once much smaller, but never had the infinite density currently postulated.
The quest to unite the two great theories of modern physics into quantum gravity has been one of the major projects of some of science's greatest minds in recent decades. Ali and Das are not claiming to have constructed a complete theory of quantum gravity, but think their work will be compatible with future paradigms.
In another proposal that harks back to a now-discarded theory, Das and Ali propose that the universe is filled with a quantum fluid made up of gravitons, particles that probably have no mass themselves but transmit gravity the way photons carry electromagnetism. The follow-up paper suggests that in the early universe these gravitons would have formed a Bose-Einstein condensate, a collection of particles that display quantum phenomena at the macroscopic scale. Moreover, the paper argues that this condensate could cause the universe's expansion to accelerate, and so explain dark energy, and might one day be the only surviving component of the universe.
Although Das and Ali's vision appears to resolve a number of problems with the dominant cosmological models, it still requires extensive elaboration to test whether it has even larger problems of its own.
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