<p>The universe is uniform and not spinning or stretching in any particular direction, scientists using data from the European Space Agency's Planck satellite have confirmed.<br /><br /></p>.<p>Looking out into the night sky, we see a clumpy universe: planets orbit stars in solar systems and stars are grouped into galaxies, which in turn form enormous galaxy clusters.<br /><br />However, cosmologists assume this effect is only local: that if we look on sufficiently large scales, the universe is actually uniform.<br /><br />The vast majority of calculations made about our universe start with this assumption: that the universe is broadly the same, whatever your position and in whichever direction you look.<br /><br />If, however, the universe was stretching preferentially in one direction, or spinning about an axis in a similar way to the Earth rotating, this fundamental assumption, and all the calculations that hinge on it, would be wrong.<br /><br />Now, scientists from University College London and Imperial College London have put this assumption through its most stringent test yet and found only a 1 in 121,000 chance that the universe is not the same in all directions.<br /><br />To do this, they used maps of the cosmic microwave background (CMB) radiation: the oldest light in the universe created shortly after the Big Bang.<br /><br />The maps were produced using measurements of the CMB taken between 2009 and 2013 by the European Space Agency's Planck satellite, providing a picture of the intensity and, for the first time, polarisation of the CMB across the whole sky.<br /><br />Previously, scientists had looked for patterns in the CMB map that might hint at a rotating universe. The new study considered the widest possible range of universes with preferred directions or spins and determined what patterns these would create in the CMB.<br /><br />A universe spinning about an axis, for example, would create spiral patterns, whereas a universe expanding at different speeds along different axes would create elongated hot and cold spots.<br /><br />The results show that none were a match, and that the universe is most likely directionless.<br /><br />"This work is important because it tests one of the fundamental assumptions on which almost all cosmological calculations are based: that the universe is the same in every direction," said Stephen Feeney, from the Department of Physics at Imperial.<br /><br />"If this assumption is wrong, and our universe spins or stretches in one direction more than another, we'd have to rethink our basic picture of the universe," said Feeney.<br /><br />"We have put this assumption to its most exacting examination yet, testing for a huge variety of spinning and stretching universes that have never been considered before.<br /><br />"When we compare these predictions to the Planck satellite's latest measurements, we find overwhelming evidence that the universe is the same in all directions," he said.<br />The study was published in the journal Physical Review Letters.</p>
<p>The universe is uniform and not spinning or stretching in any particular direction, scientists using data from the European Space Agency's Planck satellite have confirmed.<br /><br /></p>.<p>Looking out into the night sky, we see a clumpy universe: planets orbit stars in solar systems and stars are grouped into galaxies, which in turn form enormous galaxy clusters.<br /><br />However, cosmologists assume this effect is only local: that if we look on sufficiently large scales, the universe is actually uniform.<br /><br />The vast majority of calculations made about our universe start with this assumption: that the universe is broadly the same, whatever your position and in whichever direction you look.<br /><br />If, however, the universe was stretching preferentially in one direction, or spinning about an axis in a similar way to the Earth rotating, this fundamental assumption, and all the calculations that hinge on it, would be wrong.<br /><br />Now, scientists from University College London and Imperial College London have put this assumption through its most stringent test yet and found only a 1 in 121,000 chance that the universe is not the same in all directions.<br /><br />To do this, they used maps of the cosmic microwave background (CMB) radiation: the oldest light in the universe created shortly after the Big Bang.<br /><br />The maps were produced using measurements of the CMB taken between 2009 and 2013 by the European Space Agency's Planck satellite, providing a picture of the intensity and, for the first time, polarisation of the CMB across the whole sky.<br /><br />Previously, scientists had looked for patterns in the CMB map that might hint at a rotating universe. The new study considered the widest possible range of universes with preferred directions or spins and determined what patterns these would create in the CMB.<br /><br />A universe spinning about an axis, for example, would create spiral patterns, whereas a universe expanding at different speeds along different axes would create elongated hot and cold spots.<br /><br />The results show that none were a match, and that the universe is most likely directionless.<br /><br />"This work is important because it tests one of the fundamental assumptions on which almost all cosmological calculations are based: that the universe is the same in every direction," said Stephen Feeney, from the Department of Physics at Imperial.<br /><br />"If this assumption is wrong, and our universe spins or stretches in one direction more than another, we'd have to rethink our basic picture of the universe," said Feeney.<br /><br />"We have put this assumption to its most exacting examination yet, testing for a huge variety of spinning and stretching universes that have never been considered before.<br /><br />"When we compare these predictions to the Planck satellite's latest measurements, we find overwhelming evidence that the universe is the same in all directions," he said.<br />The study was published in the journal Physical Review Letters.</p>