Is the Universe Spinning?
The consequences of a spinning universe would be profound because a cornerstone of modern cosmology is that the universe has no preferred orientation.
In a study of over 15,000 galaxies by Michael Longo and co-investigators at the University of Michigan, the researchers report that spiral galaxies preferential spin clockwise or counter clockwise depending what hemisphere of the sky they are in.
Longo sampled over 15,000 galaxies in the extensive Sloan Digital Sky Survey. The galaxies extend out to little more than 600 million light-years from Earth, less than 1/20 the distance to the farthest observed galaxies to date.
Looking northward, above the plane of our Milky Way, he found that more than half of the spirals were spinning in a counterclockwise direction in the sky. This overabundance seems small, only seven percent of the total observed galaxy sample. But the odds of it being purely due to chance are a one in a million say the researchers.
If the whole universe is rotating, then an excess number of galaxies on the opposite part of the sky, below the galactic plane, should be whirling in a clockwise direction. And indeed they are according to a separate 1991 survey of 8287 spiral galaxies in the southern galactic hemisphere.
The Sloan survey is largely restricted to the northern galactic hemisphere of the sky. An important further test of these findings will be to confirm if there is indeed an excess of right-handed spiral galaxies in the southern hemisphere. This research is currently underway by Longo.
Galaxies spin, stars spin, and planets spin. So, why not the whole universe? The consequences of a spinning universe would be profound. The cornerstone of modern cosmology is that the universe is homogeneous and isotropic - it has no preferred orientation and looks the same in all directions.
On the face of it, the claim of a spin axis would seem anti-Copernican. In other words, the universe has a preferred axis, which means there is indeed a special direction in space.
A left-handed and right-handed imprint on the sky as reportedly revealed by galaxy rotation would imply the universe was rotating from the very beginning and retained an overwhelmingly strong angular momentum. This could imply that the primeval Big Bang universe had rotation energy on a vast scale. Or at least there were powerful vorticies in the primeval fireball. The galaxy spin direction is fossil evidence from these vorticies. Likewise, the rotation and revolution of our solar system's planets is a relic of the spinning gas and dust disk that encircled the newborn sun.
Such a "45-rpm" universe hasn't been predicted by any cosmology theory. In fact it would challenge inflation theory that strives to iron out any inhomogeneities in the universe.
The Sloan survey analysis could also be circumstantial evidence that what we see is merely part of a much larger and more homogeneous universe that extends far beyond our visible event horizon of our localized "spinning" universe.
This isn't the first time astronomers claimed to have observed a carousel universe. The cosmic microwave background from the big bang had suspected anomalies that were once suggested as evidence of rotation, but were later dismissed as instrumental effects.
This result might just be a statistical fluke. Or is it somehow biased because we are only looking at the local universe?
What is very curious to me is that the Milky Way's own spin axis roughly aligns to the universe's purported spin axis within just a few degrees, as deduced from the two galaxy surveys. That seems very anti-Copernican too. It has also been used to bolster biblical creationist arguments that we are at the "center" of the universe.
Invoking a familiar phrase from Carl Sagan, one cosmologist reminded me that: "extraordinary claims require extraordinary evidence."
Image credits: NASA, NSF