Are The Galaxies In Our Universe More Right-Handed… Or Left-Handed?


It’s called mirror symmetry and it has everything to do with a recent study done by physics professor Michael Longo and a team of five undergraduates from the University of Michigan. Their work encompasses the rotation direction of tens of thousands of spiral galaxies cataloged by the Sloan Digital Sky Survey. What they’re looking for is the shape of the Big Bang… and what they found is much more elaborate than they thought.

By utilizing SDSS images, the team began looking for mirror symmetry and evidence the early universe spun on an axis. “The mirror image of a counter-clockwise rotating galaxy would have clockwise rotation. More of one type than the other would be evidence for a breakdown of symmetry, or, in physics speak, a parity violation on cosmic scales.” Longo said. However, there seems to be a certain “spin preference” when it comes to spiral galaxies toward the north pole of the Milky Way. Here they found an abundance of left-handed, or counter-clockwise rotating, spirals – an effect which extended beyond an additional 600 million light years.

“The excess is small, about 7 percent, but the chance that it could be a cosmic accident is something like one in a million,” Longo said. “These results are extremely important because they appear to contradict the almost universally accepted notion that on sufficiently large scales the universe is isotropic, with no special direction.”

On the other hand, be it left or right, Galaxy Zoo has done some very interesting research into mirror symmetry as well. In conjunction with the Sloan Digital Sky Survey, the team also involved the public for their input – a total of 36 million classifications for 893,212 galaxies from 85,276 users. The GZ study is absolutely fascinating and took every variable into account.

“We wish to establish the large scale statistical properties of the galaxy spins. Although there is some level of uncertainty in the overall number counts, it is still possible to look for a dipole, for example, in the spin distributions.” says Kate Land, et al. “Curiously, the dipoles from these two analyses are in completely opposite directions. The samples cover different amounts and parts of the sky, with SDSS mainly in the Northern hemisphere and the sample of Sugai & Iye (1995) predominantly in the Southern hemisphere. In both cases the dipoles tend to point away from the majority of the data but neither analysis fits for a monopole or takes account of their partial sky coverage in assessing the dipole. With incomplete sky coverage the spherical harmonic decomposition is no longer orthogonal and for a sample covering less than half of the sky it is hard to tell the difference between a monopole (an excess of one type over the other) and a dipole (an asymmetry in the distribution).”

So what’s the end result? Well, chances are good that our universe was born spinning… but like any family, there isn’t much evidence one way or another that says most members have to be right – or left – handed. It’s more about how we, as humans, perceive them…

Original Story Source: University of Michigan New Service. For further information, read Galaxy Zoo: The large-scale spin statistics of spiral galaxies in the Sloan Digital Sky Survey.

22 Replies to “Are The Galaxies In Our Universe More Right-Handed… Or Left-Handed?”

  1. If you look at a galaxy from the top and it spins clockwise, look it from under and it’ll be counter-clockwise.

    How do one determine the “top” or “bottom” of a galaxy in the void?

    1. Hi Dave, this was one of the things we explained a lot to people on Galaxy Zoo when we did this. Basically, you’re right – clockwise or counterclockwise is not an intrinsic property of the galaxy itself. But even so, if there seems to be a preferred direction (whichever it is) from one point of view, then something weird is going on. If we looked and found more counterclockwise in the northern sky, and more clockwise in the southern sky, then we’d be seeing a general bias across the universe. If we looked out in every direction and saw an excess, that would be about as worrying as looking around in the street and seeing that all people were facing left from your point of view – you would wonder what on earth was going on! Hope that makes some sense.

      1. Does the survey take into account spiral galaxies that we can’t accurately observe because they are edge on or are at a sharp enough angle that it’s rotation in relation to our observation isn’t possible. I understand what you are saying above but if there is a greater percentage, however small, of clock-wise galaxies that we can’t identify in that group then the 7 percent discrepancy shrinks to an even smaller percentage. Another observer in another galaxy, far, far away might see more of those galaxies that we can’t observe (which may or may not have more clock-wise galaxies) and by chance might see less of the, what we think of as more dominant, counter-clockwise galaxies and determine that there appears to be no dominance of handedness. Maybe the spirals we can’t categorize are such a small sample that it doesn’t have an impact.

      2. It is possible to determine the rotation of galaxies when seen edge-on by using Dopler shifts. If a galaxy is spinning counter-clockwise, the stars on the “left side” of the edge-on galaxy would be moving toward us, while the stars on the right-hand side would be moving away.

      3. Dave Tremblay got a point there.

        If Earth was located at a different position relative to the entire universe, our view of many galxy would be flipped .. and the left or right count would have been different.

        Nevertheless it could be something going on.

  2. The direction a galaxy rotates, clockwise or counter clockwise, is equivalent to the direction of angular momentum. These results indicate that in our local region galactic angular momentum is pointed mostly away from us. This does mean that at any distance from us these angular momentum vectors will not be so aligned. This is one of those oddities which probably reflects a statistical fluctuation.


    1. It’s a long way from Longo’s reported result and indicating that in our local region galactic angular momentum is pointed mostly away from us!

      Not only were only ~15% of the ~200,000 galaxies selected assessed as being “L” or “R”, but there are far more than ~200,000 galaxies in our local volume. Perhaps, after a few more years’ of work, it will be found that the apparent handedness of elliptical galaxy spins nicely cancels that of the apparent handedness of spirals’ spins (and that that of the most obvious spirals – per Longo – is opposite to that of all spirals). Such a result would be of considerable interest in its own right – saying something about galaxy evolution, perhaps – but it would also make thoughts of some sort of fundamental, galaxy-scale universal handedness look like wild speculation.

  3. Just a note that the quote featured here from the Galaxy Zoo team is from a 2008 paper, rather than a direct response to the new work.

  4. i am honored to see replies here from the galaxy zoo team. i found the 2008 paper absolutely fascinating and was highly impressed with how every variable was taken into account. that paper alone was worthy of its own news story!

    1. Thanks Tammy – I just wanted to make sure people realised we weren’t saying anything directly about this new work. I’ve said elsewhere that I have my concerns, but it would be discourteous to say any more without putting work in. Watch this space.

  5. Dave Tremblay got a point there.

    If Earth was located at a different position relative to the entire universe, our view of many galxy would be flipped .. and the left or right count would have been different.

    Nevertheless it could be something going on.

  6. This reminds of the recent claim on the finestructure constant, and in that case too the different N-S observatories had internal discrepancy.

    I am with LC on this. From the description, and the excellent Cosmic Zoo paper, there is room for systematic errors if sampling edge on galaxies or a lot of sampling bias if not. Somewhere else I read on this there is a diminishing effect with distance which would fit the former. However, it seems to me Longo shows the opposite, confirmation that you should always read the paper yourself!

    Lintott himself notes that the earlier paper is not a direct response. However I find it interesting that the fig 5 in that paper has a monopole that needs adjustment for, that is of the same order as the one Longo dismisses in his analysis unless I am mistaken. (And then the remaining dipole is statistically insignificant.) Maybe there is no need for a further response. 🙂

    Moreover there may be a problem with inflation regarding this. Inflation dilutes the heck out of preexisting vorticity as well as curvature.

    And of course in general WMAP doesn’t see anomalies in the CMB. I have run out of links, but UT had an excellent article on this: “Seven-Year WMAP Results: No, They’re NOT Anomalies”, by Jean Tate on February 9, 2010. [I haven’t checked Longo’s references, which are mostly quite young. If the WMAP group has tired of the game, I may be allowed.]

    Regardless, this is all is an extraordinary claim but we have no extraordinary confirmation as of yet. On the contrary, earlier work with its seemingly solid statistical underpinning goes a long way to make the claim problematical.

    A note: the paper from Longo’s group is just him (in the arxiv version).

    1. The universe as a whole is not rotating, or if it is then physics is “lost.” The rotating universe is the Godel universe and this has closed timelike curves. Under such conditions causality is not defined.

      The rotational directions of galaxies might suggest that somehow the earliest period of the universe was some sort of spin-glass. Nodes of spin, say quantum black holes, grow by absorbing of nodes by various interaction. It poses an interesting conjecture.


      1. LC, I’m curious if you could answer a question (assuming you check back here) The idea of a spinning universe brought me back to an idea I had once thought about long ago – and I’m sure I’m not the first.

        Since everything in the universe from the micro to the macro scale appears to follow similar models of smaller objects orbiting larger (electrons -> nucleus, moons -> planets, planets -> stars, stars -> galactic center), what would be the likelihood of the missing ‘dark matter’ being concentrated into a central mass beyond our cosmic horizon and ‘dark energy’ being the gravitational effects of such a mass?

        For instance, the Big Bang. What if the singularity that started it all didn’t blow everything away but instead a relatively small percentage, a few outer layers, that formed our current universe? The expansion and such that we see being the result of this matter blasted off as we move in further extended orbits around the core of the singularity.

        If what I ask is possible, and if a larger percentage of galaxies have the same general spin, it could be evidence of our shared rotation around this central mass as evidenced by our own solar system and the rotation of the planets around the Sun. In that, while there are exceptions due to influences by other objects and direct impacts, most of the objects that orbit the Sun have the same relative direction of rotation.

        Not trying to advance a pet theory so to speak, just curious if this is at all possible and I know LC has the calculating chops to give me a (mostly) straight answer.

      2. @Justin,

        The idea the ‘big bang’ –of inflation after that, of dark matter, dark energy –are all slightly different from what your question implies your knowledge of them to be. Read the (layman section of) the wiki starting at

        use the right pane navagation tools to jump around within the linked articles.

        I too am looking forward to LC math for your question, grin.


      3. Mary, I appreciate the response. I’m relatively familiar with the standard idea of the dark items. – Dark Matter being an amount of missing or just not visible matter for galaxies to be the way that we see them without flying apart and Dark Energy being the driving energy that is causing the observed acceleration of the expansion of the universe. I am no expert by any means, however, just a curious bystander.

        I guess what my question revolves around is if there is a way that the concept of a rapidly spinning, insanely massive blackhole that is at least as massive as all the visible matter of the universe if not more could be applied so as to explain away some of these needed place holders at least somewhat and still fit the current observational data. I’m sure there’s massive holes in such an idea, but I am curious nonetheless.

        Given an object of such absolute density and mass, I would think it highly probable that part of it would recollapse, though I know things may not have worked quite the same back then as they do now. There are the examples of supernova that we see today as the stars blow out massive amounts of matter, but the core still remains and my mind can’t help but ponder if it would be possible to draw a similarity there.

      4. @Justin,

        I have heard it stated –the original state of the ‘a priori’ universe can not be achieved by any re-condensation of our current matter & energy, dark or otherwise, and I am inclined that direction myself, due to the 2nd Law of Thermodynamics and a great increase in entropy in the ensuing time interval.

        My stated reason for ‘your question indicated your ideas might be at odds with currently accepted ideas on the origins’ is shown within that link I provided… a vast amount of enlightenment exists within that link, really, pun intended –they say if you have to explain the pun it was a poorly formed one though, so if you need my pun to be explainable just ask.

        “Our universe was once in an extremely hot and dense state that expanded rapidly” implies the loss of that density and heat –these are both types of energy unknown to us now before the physical laws as we know them condensed (as it were) along with the quark-gluon soup all origination can claim as a common ground.


      5. The initial singularity of the universe did not so much exist at a place or point in space, but is (or was) a spatial region at a boundary of time. It is similar to the singularity in a black hole, which is not a point but a three dimensional region of space where the Weyl curvature diverges. This is a classical description. There is some quantum mechanical reinterpretation of the singularity, but this gets into the whole topic of quantum gravity, which I will defer for now. So in effect the singularity was a spatial region with a huge vacuum energy (quantum gravity) that decayed into subsequent spatial regions. So the singularity no more remains in part that a bit of yesterday hangs around today.

        I will leave this on a non-technical level, for singularity theorems and quantum extensions of spacetime singularities are challenging topics.


  7. Rotating with respect to what? Wouldn’t that require some external frame of reference?

Comments are closed.