For nearly a century, cosmologists have been obsessed with the question of whether gravity will eventually cause the universe to collapse in on itself in a reversal of the Big Bang, or if it will expand forever until the stars burn out. Or as Robert Frost put it, end in fire or ice.
The discovery of dark energy seemed to have settled the question. If the universe is not only expanding, but accelerating in its expansion because a powerful force is overcoming gravity at large distances, then how could it ever reverse? Instead, the dispersion might be expected to happen faster and faster until the galaxies, and maybe individual stars, lose touch with each other.
In Physical Review Letters, however, two physicists have attempted to answer the still-unsolved question of what dark energy actually is. Their model suggests dark energy will dominate the universe shortly before a “turnaround,” leading to an eventual collapse. While they cannot set a date on when this turnaround will occur, a natural choice for the strengths of forces suggests it could be quite soon.
“A single, technically natural choice for the slope ensures that the collapse is imminent and is preceded by the current stage of cosmic acceleration,” write physicists Nemanja Kaloper from the University of California, Davis, and Antonio Padilla of the University of Nottingham.
While their solution is elegant, it is not clear whether Kaloper and Padilla are actually describing the universe we live in. "It's way too early to say if it will stand the test of time, but so far it has stood up to scrutiny,” Padilla told Phys.org.
The work relies on a previous paper by the pair, which tackled the question of why observations of the size of the cosmological constant are wildly out of keeping with modeled results. Their solution is vacuum energy sequestering, an idea they describe as a “very simple reformulation of General Relativity” where the energy that exists everywhere (vacuum energy density) in the universe is prevented from contributing to the curvature of the universe, and therefore influencing gravity. The work makes the cosmological constant equal to the average of all the matter energy density in the universe that has, or will, exist.
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I hope that s.
Statistics: Posted by Dagnamski — Wed Mar 25, 2015 6:30 am