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The hypothesis that the Big Bang was a symmetric event with an initially uniform expansion that caused the whole Universe to be isotropic on large scales, has today been put into question by a discovery made by Michael Longo, physics professor at the University of Michigan in Ann Arbor.
Determining the sense of rotation (spin) of 15,158 spiral galaxies with redshifts below 0.085 in the Sloan Digital Sky Survey (SDSS), Longo and a group of 5 students, found that in the northern Galactic hemisphere, that mostly accessible to the Apache Point telescope in New Mexico used for the SDSS, there is an excess of anti-clockwise rotation.
The effect, detected out to a distance of 600 million light years but less evident in the closer galaxies, is actually rather modest, with the number of anti-clockwise galaxies exceeding the clockwise galaxies by less than 8%. However, given the large numbers of galaxies studied, this difference is more than enough to put doubts on the "spherical" Big Bang, suggesting that it was actually rotating and that this rotation was inherited by the material that formed the galaxies.
The anisotropy of the spins of the galaxies could be the consequence of this primordial rotation.
Longo expects to find a similar effect in the southern Galactic hemisphere, something which seems already confirmed by the catalogue of galactic spins made by Iye e Sugai. In this case an excess of clockwise spins is expected.
As further work on this curious effect is carried out, some caution is perhaps wise. Many works have been carried out, and are still underway, that investigate the possibility of such asymmetry in the Universe, and not all agree as to the direction of the asymmetry or even its presence.
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