Results from the most stringent test performed to date shows that the universe is not stretched in any particular direction, nor is it spinning.
Cosmologists assume that the clumpy universe we see when we look up into the sky at night is only local. The chunky effect is created by planets orbit stars in solar systems. The stars are in turn grouped into galaxies, and galaxies form enormous galactic clusters. Cosmologists assume that if we were able to see the galaxy on a sufficiently large scale, the universe would actually appear uniform.
This assumption is used in virtually all calculations made about our universe, i.e. whatever your position and in whichever direction you look, the universe is broadly the same. If the universe were however spinning about an axis in a similar way to the Earth rotating, or stretching preferentially in one direction, all the calculations that hinge on the basic assumption would be wrong.
Scientists from Imperial College London and University College London have tested this assumption more stringently than ever before and concluded that there is only a 1 in 121,000 chance that the universe is not uniform in all directions.
The test was done by using maps of the oldest light in the universe created shortly after the Big Bang, called the cosmic microwave background (CMB) radiation.
The European Space Agency’s Planck satellite measured CMB between 2009 and 2013 and the research team used these measurements to create the maps. For the first time, a picture of the polarization (orientation) and intensity of the CMB across the whole sky is available.
Previous studies tried to find patterns in the CMB map that might indicate a rotating universe. The new study took the opposite approach by determining what patterns the widest possible range of universes with preferred directions or spins would create in the CMB. Elongated hot and cold spots will for instance be created by a universe expanding at different speeds along different axes, while spiral patterns would indicate a universe spinning about an axis.
Working with a team led by Daniela Saadeh at University College London, Dr Stephen Feeney from the Department of Physics at Imperial, searched for these patterns in the CMB that had been observed. The results were published in the journal Physical Review Letters and show that none were a match, resulting in the conclusion that the universe is probably directionless.
Feeney noted that if the assumption that the universe is the same in every direction is wrong, our basic picture of the universe will have to be relooked. This study is important in that it has shown that our universe does not spin or stretch in one direction more than another, and our current cosmological calculations seem to be correct. He added that during the study a huge variety of spinning and stretching universes that have never been considered before were included. This has tested the basic assumption more stringently that it has ever been tested before. When the study’s predictions are compared to the Planck satellite’s latest measurements, overpowering evidence is found that the universe is the same in all directions.
The results were published the journal Physical Review Letters.