# How is it possible for the earth to rotate at different speeds at different latitudes? **URL:** \ **Category:** Factual Questions\ **Created:** [September 19, 2014, 2:52pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932 "2014-09-19T14:52:15Z")\ **Posts on this page:** 17\ **Page:** 2
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [September 20, 2014, 2:22am UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/21 "2014-09-20T02:22:10Z")
> [@Senegoid](#): > > Somewhere over the years, I read an explanation of Relativity that touched on exactly this point. Yes, the outer edge of a record ages more slowly than the inner-most track, and the amount of this difference is computable and measurable. It was some figure on the order of a small number of billionths of a second (per revolution, I take it). But the Earth is much bigger and spins much faster than a record. This is why people from the tropics are so much younger than Eskimos. 😉 ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [September 20, 2014, 3:52am UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/22 "2014-09-20T03:52:31Z")
And if you spin a long skinny thing like a propeller so fast that the far end starts going through the sound barrier, bad ju ju starts to happen. Much excitement soon ensues. 😃 ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [September 20, 2014, 7:38am UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/23 "2014-09-20T07:38:36Z")
> [@jtur88](#): > > If you mean precisely, if carried out to many decimal places, there is a difference in angular velocity at different latitudes. Which is why we have tides, which are, after all, on the surface of the earth. Wait, what? Tides aren’t caused by angular velocity differential. Coriolis force is, though. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [September 20, 2014, 8:37am UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/24 "2014-09-20T08:37:14Z")
Get together a bunch of drag queens (optional). Now have them do a kick line, with the guy on the left end as the “hub.” Have the others circulate around him like a pinwheel, with the guy on the right as the whip. All “Lefty” has to do is make tiny steps while standing still. “Righty” has to haul ass. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [September 20, 2014, 9:25am UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/25 "2014-09-20T09:25:56Z")
Didn’t we have some nutter here once who argued that the two hemispheres of the earth rotate in opposite directions? ---
**Author:** ![The\_Great\_Unwashed](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_great_unwashed/32/4791_2.png) [@The\_Great\_Unwashed](https://boards.straightdope.com/u/The_Great_Unwashed)\ **Post date:** [September 20, 2014, 10:12am UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/26 "2014-09-20T10:12:17Z")
> [@Mangetout](#): > > Didn’t we have some nutter here once who argued that the two hemispheres of the earth rotate in opposite directions? If we didn’t we should get one, because he sounds like a hoot. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [September 20, 2014, 12:36pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/27 "2014-09-20T12:36:16Z")
> [@Malacandra](#): > > Wait, what? Tides aren’t caused by angular velocity differential. Yes they are. If all parts of the fluid oceans rotated at all times with exactly the same angular velocity with the continents as an unvarying constant, there would be no tides. ---
**Author:** ![The\_Great\_Unwashed](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_great_unwashed/32/4791_2.png) [@The\_Great\_Unwashed](https://boards.straightdope.com/u/The_Great_Unwashed)\ **Post date:** [September 20, 2014, 12:43pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/28 "2014-09-20T12:43:52Z")
> [@jtur88](#): > > If you mean precisely, if carried out to many decimal places, there is a difference in angular velocity at different latitudes. Which is why we have tides, which are, after all, on the surface of the earth. Not what [NOAA have to say](http://oceanservice.noaa.gov/education/kits/tides/tides03_gravity.html), nor [HowStuffWorks](http://science.howstuffworks.com/environmental/earth/geophysics/tide-cause.htm), nor [Wikipedia](http://en.wikipedia.org/wiki/Tide), each of which attribute tides to the gravitational effects of the moon and the sun. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 20, 2014, 12:45pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/29 "2014-09-20T12:45:30Z")
> [@Mangetout](#): > > Didn’t we have some nutter here once who argued that the two hemispheres of the earth rotate in opposite directions? The hemispheres do rotate in opposite directions. You can see for yourself. Stand on the South pole you’ll see that it rotates clockwise. Stand on the North pole and you’ll see that it rotates counterclockwise. Logically you have to derive that at the Equator it doesn’t rotate at all. The really hard part is figuring out the rotation at the East and West poles. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 20, 2014, 1:10pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/30 "2014-09-20T13:10:06Z")
“Clockwise from the north” and “counterclockwise from the south” are the same direction. And tides are caused by the gravitational influence of other bodies, mostly the Sun and Moon. They, in turn, like all motions on the surface, result in slightly different angular velocities at different points. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [September 20, 2014, 1:15pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/31 "2014-09-20T13:15:54Z")
> [@Flywheel](#): > > [Obligatory Calvin & Hobbes link.](http://assets.amuniversal.com/d73efdd0dece013171ac005056a9545d) Great username/post/thread combo! > [@Chronos](#): > > “Clockwise from the north” and “counterclockwise from the south” are the same direction. Whoosh. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [September 20, 2014, 2:13pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/32 "2014-09-20T14:13:14Z")
> [@The\_Great\_Unwashed](#): > > Not what [NOAA have to say](http://oceanservice.noaa.gov/education/kits/tides/tides03_gravity.html), nor [HowStuffWorks](http://science.howstuffworks.com/environmental/earth/geophysics/tide-cause.htm), nor [Wikipedia](http://en.wikipedia.org/wiki/Tide), each of which attribute tides to the gravitational effects of the moon and the sun. Note that I did not say that the angular velocity causes tides. I said the tides, when observed, reflect a differential in angular velocity. Angular velocity is an observed metric of a phenomenon, not a cause of the phenomenon that is observed. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [September 20, 2014, 2:33pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/33 "2014-09-20T14:33:45Z")
> [@jtur88](#): > > there is a difference in angular velocity at different latitudes. Which is why we have tides, [Quote=me] Wait, what? Tides aren’t caused by angular velocity differential. [/quote] > [@jtur88](#): > > Yes they are. If all parts of the fluid oceans rotated at all times with exactly the same angular velocity with the continents as an unvarying constant, there would be no tides. > [@jtur88](#): > > Note that I did not say that the angular velocity causes tides. I said the tides, when observed, reflect a differential in angular velocity. Angular velocity is an observed metric of a phenomenon, not a cause of the phenomenon that is observed. I’m struggling both to understand what you’ve most recently said, and how it squares with the two previous quotes, where you seem to have said that the difference in angular velocity causes tides. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [September 20, 2014, 3:58pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/34 "2014-09-20T15:58:38Z")
> [@jtur88](#): > > Maybe even continental drift is a form of one part of the surface rotating at a different speed than another. Nope. This is not what causes plate tectonics (“Continental drift” is a very outdated term for the concept) ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [September 20, 2014, 4:10pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/35 "2014-09-20T16:10:23Z")
> [@Smeghead](#): > > How would it be possible for it NOT to do that? Strange eons, mate. On the great plains of Tindalos, in the folds of time, are triangular spheres and straight curves, all points of which rotate at the same relative speed. Iah ! Iah ! ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [September 20, 2014, 5:55pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/36 "2014-09-20T17:55:50Z")
> [@TriPolar](#): > > The hemispheres do rotate in opposite directions. You can see for yourself. Stand on the South pole you’ll see that it rotates clockwise. Stand on the North pole and you’ll see that it rotates counterclockwise. Logically you have to derive that at the Equator it doesn’t rotate at all. The really hard part is figuring out the rotation at the East and West poles. Yeah, im pretty sure this guy thought crossing the equator was like jumping off a train onto one going the other way. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [September 20, 2014, 6:49pm UTC](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932/37 "2014-09-20T18:49:20Z")
> [@Mangetout](#): > > Yeah, im pretty sure this guy thought crossing the equator was like jumping off a train onto one going the other way. I could have gone that way, but it seemed too ridiculous. Anyone convinced of that explanation is even nuttier than I am or just joking. I think the OP may have seen an inaccurate description that did say rotation at different rates and came here for an explanation. As Cronos pointed out, rotation direction is relative to the observer. Consider counter rotating objects on the same axis, they only seem to counter rotate based on a fixed position apart from the object. With either of the objects as the only reference the other one only seems to be rotating at a different rate, not a different direction. Or I suppose you could assume any object rotating at a different rate is counter rotating in that circumstance. [Previous page](https://boards.straightdope.com/t/how-is-it-possible-for-the-earth-to-rotate-at-different-speeds-at-different-latitudes/698932.md?page=1)