Most current cosmological studies assume that the universe behaves identically in every direction. If this assumption were to fail, a large number of analyses of the cosmos and its content would be flawed.
Using data from the European Space Agency's Planck satellite, researchers have confirmed what cosmologists have assumed all along - our universe expands the same way in all directions. "We're very glad that our work vindicates what most cosmologists assume. For now, cosmology is safe," said study first author Daniela Saadeh from University College London.
‘Using data from the European Space Agency's Planck satellite, researchers have confirmed - our universe expands the same way in all directions.’
The new study, published in the journal Physical Review Letters, studied the cosmic microwave background (CMB) which is the remnant radiation from the Big Bang. "The finding is the best evidence yet that the universe is the same in all directions," she said.
"Our current understanding of the universe is built on the assumption that it doesn't prefer one direction over another, but there are actually a huge number of ways that Einstein's theory of relativity would allow for space to be imbalanced. Universes that spin and stretch are entirely possible, so it's important that we've shown ours is fair to all its directions," she explained.
The team used measurements of the CMB taken between 2009 and 2013 by the European Space Agency's Planck satellite. The spacecraft recently released information about the polarisation of CMB across the whole sky for the first time, providing a complementary view of the early universe that the team was able to exploit.
The researchers modelled a comprehensive variety of spinning and stretching scenarios and how these might manifest in the CMB, including its polarisation. They then compared their findings with the real map of the cosmos from Planck, searching for specific signs in the data.
"We calculated the different patterns that would be seen in the cosmic microwave background if space has different properties in different directions. Signs might include hot and cold spots from stretching along a particular axis, or even spiral distortions," Saadeh noted.
"We then compare these predictions to reality. This is a serious challenge, as we found an enormous number of ways the Universe can be anisotropic," collaborating author Stephen Feeney from Imperial College London added.
The researchers calculated the odds that "the universe prefers one direction over another at just one in 121,000".