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Is The Earth's Rotation Changing?

Posted by Hemos on from the moving-slowly-along dept.

Roland Piquepaille writes "We all know about the current controversies associated with the ozone layer or the global warming phenomenon. Now, the NASA's Earth Science Enterprise (ESE) is warning us that atmospheric changes or El Niño events can affect the Earth's rotation. During El Niño years, for example, the rotation of the Earth may slow ever so slightly because of stronger winds, increasing the length of a day by a fraction of a millisecond. David A. Salstein, an atmospheric scientist from Atmospheric and Environmental Research, Inc., led a recent study about this possible effect. Salstein looked at meteorological and astronomical measurements from different sources and found they were in good agreement. Check this column for a synthesis. For technical explanations, images and animations, please read this NASA paper, Changes in the Earth's rotation are in the wind."

24 of 372 comments (clear)

  1. well known by lovebyte · · Score: 5, Funny

    This has been known since 1951.

    --

    I'll do it for cheesy poofs.

    1. Re:well known by trotski · · Score: 5, Funny

      Pfffff..... how can the earth rotate if the earth is flat?!?! The realities of the earth have been established a long time ago; it is a plane board, sort of like a game board mounted on top of an infinate tower of turtles. All this stuff about the earth being round? Reactionary bull shit. Check out the truth:

      A flat earth, it's not just a good idea; it's the truth.

      --

      "Entropy is the bad-guy, and he is everywhere"
  2. Days getting longer? by kaszeta · · Score: 5, Funny

    The days are getting longer? Cool, I could use an extra five minutes each day to read Slashdot...

  3. SUPERMAN! by Acidic_Diarrhea · · Score: 5, Funny

    I wish Superman would get off his ass and do that whole 'spin-the-world' backwards so we could go back in time and prevent the term 'El Nino' from being invented - which so many bad stand-up comics have used to no end. Also, I would not buy my Voodoo 3 card.

    --
    I hate liberals. If you are a liberal, do not reply.
  4. Wait a second... by Anonymous Coward · · Score: 5, Funny

    this is really just a fake news to hype up "The Core", isn't it?

  5. OK, there's only one way to solve this ... by BabyDave · · Score: 4, Funny

    Everybody run east as fast as you can, to speed the Earth up again!

    /me waits for hundreds of pedantic comments explaining why this wouldn't work

    1. Re:OK, there's only one way to solve this ... by unicron · · Score: 4, Funny

      This wouldn't work. The majority of /. readers, myself included, upon running would either have a heart attack, puke, or just get bored and go home.

      --
      Finally, math books without any of that base 6 crap in them.
    2. Re:OK, there's only one way to solve this ... by pclminion · · Score: 4, Informative
      Sorry, I'm going through this article trying to correct as much bad physics as I can, even though I know you meant this as a joke. So here's my pedantic comment:

      Everybody run east as fast as you can, to speed the Earth up again!

      Disregarding the honest mistake (you need to run West, not East)... This would actually work, as long as everyone *keeps running*. As soon as they stop running, the angular momentum which was transferred to the Earth will be transferred back to the runners. You can't change the total angular momentum of the system.

      In order to speed up the Earth you would have to use a rocket or some kind of cannon which is capable of flinging material *clear off* Earth's surface, never to return. Even then, the amount of energy contained in the rotation of the Earth is *astonishingly huge*. It's doubtful we'll ever come up with anything that could make even the slightest impact on it.

  6. Old news? by AuraSeer · · Score: 4, Interesting

    I'm sorry, but isn't this widely known? I learned about this effect in my 9th grade science class. Uneven heating of the surface can cause uneven wind resistance blah blah blah... and several million years from now, the day might be a few seconds longer.

    Does simply adding the words "El Nino" makes people think this is a new, important idea? The planet's rotation speed is also affected by the impact of meteors and space dust, but I don't see anyone publishing studies to measure that infinitesimal effect.

  7. But what about the moon? by OldAndSlow · · Score: 5, Interesting

    It seems to me that whatever changes strong winds make in the earth's rotation must be temporary because of the conservation of angular momentum. When the wind pick up, the earth slows down. Wehn the winds die down, the earth speeds up again.

    If you really want to get agitated about the earth's rotation slowing down, consider the moon. Tides act as a brake on the earth/moon system. So the rotation of the earth slows, and the moon (to conserve angular momentum) moves ever so slowly away from the earth.

    1. Re:But what about the moon? by tbmaddux · · Score: 4, Informative
      whatever changes strong winds make in the earth's rotation must be temporary because of the conservation of angular momentum.
      This would be true if you neglected dissipation/friction, which you shouldn't.
      If you really want to get agitated about the earth's rotation slowing down, consider the moon.
      Most studies of this sort of thing do have to account for the moon and its tidal coupling to the earth as a leading-order effect on the earth's rotation. The linked article is exploring atmospherics as a second-order effect. Another important second-order effect on the earth's rotation is glacial isostatic adjustment, the viscoelastic response of the earth to loading/unloading from the different mass distributions of glaciers and oceans on the earth's surface. As the earth changes shape, its spin rate changes.

      This adjustment also important to us because it is of the same order at many locations as the change in sea level due to the temperature of the ocean.

      --
      Can't you see that everyone is buying station wagons?
    2. Re:But what about the moon? by pclminion · · Score: 4, Informative
      It seems to me that whatever changes strong winds make in the earth's rotation must be temporary because of the conservation of angular momentum. When the wind pick up, the earth slows down. Wehn the winds die down, the earth speeds up again.

      No. Friction is a non-conservative force. The energy is irreversibly transformed into heat. *Total energy* is conserved, but there is no physical law saying that kinetic energy must remain kinetic, or rotational must remain rotational.

      Imagine a bathtub full of water, with the water sloshing around in the bathtub. As the sloshing water rubs against the sides of the tub, it transfers energy to the tub in the form of heat. Eventually the sloshing ceases, and all the kinetic energy the water had is now converted to heat. The process is irreversible -- you don't suddenly see the bathtub *cooling down* as the water spontaneously starts sloshing again.

      I mean, this is basic thermodynamics.

  8. Re:Hey, subscriptions aren't working... by arnie_apesacrappin · · Score: 4, Funny
    cause I don't have one, and the title is a red-bar

    Try moving towards the screen really fast. It should look green then. Of course, make sure you stop before you run into the screen, because a collision with a monitor at speeds close to the speed of light might hurt.

    --

    Still, with a plan, you only get the best you can imagine. I'd always hoped for something better than that. -CP

  9. Short Term? by Acidic_Diarrhea · · Score: 5, Insightful
    When you're dealing in matters of planets, short-term is a thousand years.

    And what are you talking about with your statement about the change being "unmeasurable"? The point of the article is that it is being measured.

    --
    I hate liberals. If you are a liberal, do not reply.
  10. Re:Oh great, by stinky+wizzleteats · · Score: 5, Funny

    This is clearly a problem with SUVs. A vehicle as heavy as an SUV puts down a trememdous amount of torque when it moves, and this action, combined with the great suburban conspiracy of living to the East of their workplace (you go faster going home, so more torque to slow down the Earth), are creating this problem.

  11. Mountains do the same thing by silvaran · · Score: 4, Informative

    When snow collects on mountains, it increases the earth's radius ever so slightly... so the actual day span increases by a fraction of a second. It's a small fraction though, but it still exists. This happens more during the winter when the earth is farther away from the sun. Anyways, it's nothing to get worried about. We've been dealing with rotational inconsistencies for awhile.

    What's the average length of a day? Something like 23 hours, 59 minutes and 56 seconds or something like that. Which is why we have a leap year:

    If the year is divisible by 4
    Unless it's divisible by 100
    But always if it's divisible by 400

    So hey... leapYear = ((year%400)==0)||(((year%4)==0)&&((year%100)!=0));

    Can someone answer this though: Do we manually synchronize our clocks every once and awhile (say every few years anyways) just to make sure? I heard a rumor about it (most people have to reset their clocks after the power goes out anyways, and PC clocks are horribly inaccurate), so is this true?

    1. Re:Mountains do the same thing by pclminion · · Score: 4, Informative
      When snow collects on mountains, it increases the earth's radius ever so slightly... so the actual day span increases by a fraction of a second.

      True, but when the snow melts in spring the rotation will speed back up again (rotational inertia decreasing as mass moves downward).

      This is fundamentally different from wind friction, which is a non-conservative force which *irreversibly* slows the Earth's rotation. The only way it might speed up again is if the wind started blowing the opposite direction with equal force.

      This happens more during the winter when the earth is farther away from the sun.

      The Earth is *nearer* the sun in the Northern Winter. It is the tilt of the rotational axis which produces winter, not distance from the sun. The moment of closest approach (perihelion) actually precesses very slowly (arcseconds per year). In short, there is utterly no relationship between distance to the sun and the seasons we experience on Earth.

      Do we manually synchronize our clocks every once and awhile (say every few years anyways) just to make sure?

      It depends what kind of clock. The cesium clock is the scientific *definition* of a second, therefore it doesn't need to be calibrated since everything else is calibrated to *it*. How often you need to synchronize your clock depends on how accurate it is (usually measured in parts per million, or parts per trillion for accurate clocks).

  12. Re:Well, duh by Jugalator · · Score: 4, Funny

    In two months.

    http://www.poleshiftprepare.com/poleshift.htm

    "I myself have outstanding personal knowledge and conviction that the cataclysms will occur in May 2003, which is why I am openly stating this on the Internet, and appealing to similar individuals who wish to take steps in preparing for it."

    IT MAY SEEM FUNY NOW BUT U THANK HIM & HIS OUTSTNADING CONVICTION TO TELL US ON TEH INTRANET WHEN TEH POLE SHFITS MAY 2003!!!11 PREPAR URSELF!!!

    ^-- How my IQ dropped after reading his article... I guess it's the Internet we love and hate. :-) Don't forget to visit the main page either, complete with pictures of his Survival Tents. This sure is stuff for Something Awful. =)

    --
    Beware: In C++, your friends can see your privates!
  13. since 1900 by peter303 · · Score: 4, Insightful

    Well-known branch of astronomy called "LOD" or length of day measurements. Changes up to a millisecond or so each year. Atomic clocks and satellites allowed microsecond precision now. Weather, magnetic storms, earthquakes, ocean currents all tought to affect LOD.

  14. This story is a plant advertising a movie by goombah99 · · Score: 4, Insightful
    This smells a lot like a planted science article advertising the movie The Core ( opening march 28) .

    Just like the last one planted by the same folks. Who? its a promo for the movie "the CORE" about what? the slowing rotation of the earth's core (caused by a secret weapon project).

    the last one was also in slash dot too. its was on drilling to the earths core with advanced materials. (sorry I cant locate the slashdot article right now, though I did see the last one about the mars core

    in that case the movie distibuter's publicity folks were using real science and real information. They were just responible for planting news articles about it strategically. this smells the same, and the timing makes it clear.

    --
    Some drink at the fountain of knowledge. Others just gargle.
  15. Main topic. by Fastlane · · Score: 4, Insightful

    It seems everyone here is missing the main topic. (And not just the ones modded Offtopic)
    The main cause of the earth's rotation slowing _during EL Nino years_ is the change in the angular momentum of the earth. This means, that as some point, the angular momentum will change BACK!! Hence, CONSERVATION of momentum. The net effect in the long run is no change in the earth's rotational period due to this phenomenon.
    However, it has been a well known fact that the earth's day will gradually grow longer. One of the causes of this is the earth becoming tidally locked with the moon, the way the moon is now. It's just a function of relative gravitational force.
    And offtopic: The geologic record does indicate the magnetic poles reversing every 10k-12k years. You'll have to research the 'why' on your own though. I only remember from my astronomy classes that it does...

    The truth is out there, but the server is down or not responding.

  16. Karma to burn, baby by Quila · · Score: 4, Insightful

    It appears the link between warming and rotation is pretty good. What is not good is the link between man's action and what appears to be part of the Earth's normal warming and cooling cycles.

    Besides, I thought we were to all have died from Global Cooling by now, at least that was what they were saying in the 1970s. How did cooling switch to warming so fast?

  17. All together now... by Anonymous Coward · · Score: 5, Funny

    Ok, everyone, all over the planet...

    Face east, and...

    BLOW...

    now face west and...

    SUCK
    ...and ... EAST ... BLOW! ... WEST ... SUCK! ... EAST...

  18. Every week by rgf71 · · Score: 5, Funny

    I've known this for eons. The earth's rotation slows down to a crawl every Monday, and then speeds up really really fast on Saturday/Sunday. Then it slows down again come Monday morning.