# Spiral galaxies clockwise vs. counter - what's the difference? **URL:** \ **Category:** Factual Questions\ **Created:** [October 13, 2007, 8:36pm UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609 "2007-10-13T20:36:33Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![happywaffle](https://avatars.discourse-cdn.com/v4/letter/h/ee59a6/32.png) [@happywaffle](https://boards.straightdope.com/u/happywaffle)\ **Post date:** [October 13, 2007, 8:36pm UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/1 "2007-10-13T20:36:33Z")
[Galaxy Zoo](http://www.galaxyzoo.org) is a neato project to classify different galaxies, but one part of it mystifies me; when you classify a galaxy as a spiral, it asks whether you think it’s rotating clockwise or counterclockwise. What difference does this make? Assuming all spirals are scattered in every different orientation, then any spiral galaxy can be said to be rotating clockwise or counterclockwise, depending on which way it happens to be facing you. (I _really_ thought about this before posting to make sure I was visualizing it correctly!) ---
**Author:** ![KlondikeGeoff](https://avatars.discourse-cdn.com/v4/letter/k/3e96dc/32.png) [@KlondikeGeoff](https://boards.straightdope.com/u/KlondikeGeoff)\ **Post date:** [October 13, 2007, 8:39pm UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/2 "2007-10-13T20:39:19Z")
Good question. I assume it is as seen from Earth. ---
**Author:** ![happywaffle](https://avatars.discourse-cdn.com/v4/letter/h/ee59a6/32.png) [@happywaffle](https://boards.straightdope.com/u/happywaffle)\ **Post date:** [October 13, 2007, 8:48pm UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/3 "2007-10-13T20:48:55Z")
Right, but why would they care, is my question. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [October 13, 2007, 8:54pm UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/4 "2007-10-13T20:54:14Z")
My WAG is that they want to see if they get a consistent answer from multiple people. If everyone thinks a particular galaxy is clockwise, that’s an indication of a very clear spiral pattern. If there is a lot of discrepancy, that’s an indication of an irregular or indistinct shape, and maybe it shouldn’t even be classified as a spiral. ---
**Author:** ![Omphaloskeptic](https://avatars.discourse-cdn.com/v4/letter/o/bcef8e/32.png) [@Omphaloskeptic](https://boards.straightdope.com/u/Omphaloskeptic)\ **Post date:** [October 13, 2007, 9:32pm UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/5 "2007-10-13T21:32:18Z")
There’s some recent preliminary [evidence (astro-ph preprint)](http://xxx.lanl.gov/abs/0707.3793) that spiral galaxies have a preferred rotation direction, and this classification will probably be used in extensions of that study. I don’t know how good this evidence is; the same author had another paper which made news recently, purporting to find a bias in orientations of elliptical galaxies, but that has been withdrawn with discovery of a sample bias. But it’s a cool idea, and only with the SDSS data it has become feasible to do really large-scale galaxy statistical studies like this. ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [October 14, 2007, 12:10am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/6 "2007-10-14T00:10:03Z")
[QUOTE=happywaffle] What difference does this make? Assuming all spirals are scattered in every different orientation, then any spiral galaxy can be said to be rotating clockwise or counterclockwise, depending on which way it happens to be facing you. [/QUOTE] If that assumption is true, then it follows that distribution is random. I think, actually, that’s the assumption they might test. If it turns out that there is a statistically significant bias towards either direction, that would indicate something to cause said bias. As a WAG, I’d hypothesize that if the universe has some net angular momentum, then you’d see a bias in spiral galaxy rotation. I’m sure someone will come along with a more informed hypothesis soon enough, though. ---
**Author:** ![Glazer](https://avatars.discourse-cdn.com/v4/letter/g/a88e57/32.png) [@Glazer](https://boards.straightdope.com/u/Glazer)\ **Post date:** [October 14, 2007, 12:20am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/7 "2007-10-14T00:20:34Z")
So they know if they are looking at the top or the bottom. 😃 ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [October 14, 2007, 12:28am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/8 "2007-10-14T00:28:15Z")
Paging **Angua**. ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [October 14, 2007, 1:09am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/9 "2007-10-14T01:09:12Z")
Okay, here’s my question. Are there any, (many?) spiral galaxies that we see ‘edge on’, so that the spiral isn’t clearly visible from our perspective, and if so, can we tell that they’re spirals in other ways? 🙂 ---
**Author:** ![IAmNotSpartacus](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@IAmNotSpartacus](https://boards.straightdope.com/u/IAmNotSpartacus)\ **Post date:** [October 14, 2007, 1:38am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/10 "2007-10-14T01:38:34Z")
[QUOTE=lazybratsche] As a WAG, I’d hypothesize that if the universe has some net angular momentum, then you’d see a bias in spiral galaxy rotation. I’m sure someone will come along with a more informed hypothesis soon enough, though. [/QUOTE] My further WAG would be that if there _were_ angular momentum, then perhaps a “center” of the universe could be found? ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [October 14, 2007, 4:09am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/11 "2007-10-14T04:09:51Z")
[QUOTE=chrisk] Okay, here’s my question. Are there any, (many?) spiral galaxies that we see ‘edge on’, so that the spiral isn’t clearly visible from our perspective, and if so, can we tell that they’re spirals in other ways? 🙂 [/QUOTE] There are plenty of them. For example, the stunningly beautiful [Sombrero Galaxy](http://terpsichore.stsci.edu/~summers/viz/hgast/hgast_imax_sombrero_galaxy_0510_1404x1024.jpg). It’s inclined just enough that you can see the spiral, but there are other galaxies that are so perpendicular that you can’t see anything but the edge of the disc and the bulge in the center. For example, [NGC 891](http://rao.150m.com/NGC891.html) in Andromeda. We know they are spiral galaxies because that’s the only way you can get a bulge in the center and a long line of dust and stars bisecting it. You don’t know what kind of spiral it is, how many arms it has, and the like, but you know it’s a spiral. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [October 14, 2007, 4:20am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/12 "2007-10-14T04:20:06Z")
In your link to the Galaxy Zoo, just look at the 2nd question of the FAQ. Here you go: [Zooniverse](http://www.galaxyzoo.org/faq.aspx) That is _very_ interesting. Very. ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [October 14, 2007, 5:53am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/13 "2007-10-14T05:53:36Z")
[QUOTE=KarlGauss] In your link to the Galaxy Zoo, just look at the 2nd question of the FAQ. Here you go: [Galaxy Zoo | Zooniverse - People-powered research](http://www.galaxyzoo.org/faq.aspx) [/QUOTE] > [@](#): > > Q. Why record the rotation of the galaxy when it depends on your position? A different observer on the other side of the galaxy would observe it rotating the opposite way. And shouldn’t they all be random? > A. Yes, they should be, but a recent investigation, involving many fewer galaxies, suggested that the odds of seeing a clockwise or an anticlockwise galaxy changed depending on where you look in the sky. If this is true, it suggests we’re missing something about how the Universe is organised on large scales, and so we decided - with your help - to see if the effect is real. Probably Coriolis effect. _::: d & r :::_ ---
**Author:** ![mnemosyne](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)\ **Post date:** [October 14, 2007, 6:15am UTC](https://boards.straightdope.com/t/spiral-galaxies-clockwise-vs-counter-whats-the-difference/422609/14 "2007-10-14T06:15:32Z")
[QUOTE=Sam Stone] There are plenty of them. For example, the stunningly beautiful [Sombrero Galaxy](http://terpsichore.stsci.edu/~summers/viz/hgast/hgast_imax_sombrero_galaxy_0510_1404x1024.jpg). [/QUOTE] WOW! Stunningly beautiful indeed. I was literally breathless when I first saw that image! Amazing that such a thing can exist! Sorry, nothing to really contribute to the thread, I just needed to thank **Sam Stone** for posting something so lovely!