“The first models were based on a very simple approximation where the universe is uniformly smooth and featureless, evolving the same way in all directions. Looking at the huge numbers of observations such as supernovae distances, cosmic microwave background radiation fluctuations and galaxy clustering statistics, and thinking about the many anomalies standard dark energy does not solve, I thought we had to be much more careful in the way we interpret the observations,” Dr Wiltshire said.
He said that the present universe was very lumpy and that galaxies were not uniformly distributed with huge voids hundreds of millions of light-years across.
Long before galaxies formed, matter was smoothly distributed and clock rates were the same everywhere. Now that it was “lumpy”, it was necessary to account for where the observer was when calibrating cosmic clocks.
A common analogy is that space curves around a massive object - just as a rubber sheet on a trampoline will stretch around a heavy cannon ball - and time slows down there.
“The flat edge of the rubber sheet is the reference point for our clocks. It is only the space beyond this flat edge that is expanding. Clock rates and the curvature of space can both vary gradually as you move across an expanding void.”
And, since mass slows down time, the clocks of observers in voids, where most of the empty space in the universe is, will appear to be ticking faster than the clocks of observers in galaxies.
It was this last feature, he said, that explained why dark energy was unnecessary.http://www.comsdev.canterbury.ac.nz/news/2008/080125c.shtml
