Unlike the Flat Earth Society, which was founded millennia after scholars widely accepted the spherical Earth, a Flat Universe Society would support a valid theory. But a flat universe is just one of many possible universe shapes theorists are exploring.
Credit: George Grie
MASSACHUSETTS: Just as we experience the spherical Earth as flat, the shape of the universe is not necessarily as we experience it, said researchers who are comparing measurements of left-over Big Bang radiation with computer simulations.
The idea that the fabric of the universe might curve in various directions dates back to Einstein's General Theory of Relativity, suggesting that the Earth's two-dimensional (2-D) plane curves into a third dimension to form a sphere. Cosmologists believe that the 3-D ‘plane’ of the universe may likewise curve into a fourth dimension to form some as-yet unknown shape. But until recently, it wasn't possible to test that theory.
"Recently there have been some theories that said that the creation of the universe in the shape of a torus is much more probable, even more than an infinite universe," explained Grigor Aslanyan, a doctoral student at the University of California at San Diego.
A doughnut-shaped universe?
Those theories gave Aslanyan the idea of comparing data from the Wilkinson Microwave Anisotropy Probe (WMAP) - a 7-year NASA mission that measured radiation left over from the Big Bang that released its complete data set to the public in January 2010 - with simulations based on the shape of a torus.
A torus-shaped universe could take three forms. It could be finite in all three dimensions, curving back on itself in each dimension. It could be finite in only two dimensions, and infinite in the third. Or it could be infinite in two dimensions and finite in only one.
In each case, it could be a variety of sizes; Aslanyan must compare them all to the WMAP data. To do so, his program had to step through potential sizes and orientations in tiny increments, making calculations for each and comparing those with the WMAP data.
A thousand jobs at once
With so many calculations and comparisons to make, Aslanyan quickly discovered that the problem was far more computationally demanding than his workstation could accommodate. That's when his advisor, Aneesh Manohar, suggested he connect with Open Science Grid.
"What we're doing was pretty easy to parallelise," Aslanyan said. The calculations and comparison for each shape and orientation are independent. "So we can basically run a thousand jobs at the same time."
Aslanyan used the publicly available Fortran code, which calculates the cosmic microwave background radiation (CMB) spectrum for an infinite, flat universe, and then adapted it with code he wrote in C++ - a free-form, general-purpose programming language.
The entire analysis took approximately 500,000 CPU-hours on Open Science Grid. "So far it looks like the finite case agrees with the data better than the conventional infinite case," Aslanyan said.
Ruling out certain universe shapes
According to Aslanyan, his research could also shed light on a phenomenon cosmologists have whimsically called the ‘axis of evil.’ The phenomenon is a direction in the sky in which the CMB looks different from all other directions.
Aslanyan hypothesised that a long torus, infinite in the same direction as the phenomenon, might explain those differences. When he publishes his findings, they may rule out certain shapes, or provide bounds on the sizes of certain shapes.
"We might decide to try out also some other shapes," Aslanyan said. "And then there is also a new set of experimental data being expected in a year or so from the Planck satellite, and it will provide more accurate experimental data. And so it could be done again with that data."
Originally posted by the International Science Grid This Week
