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Is The Earth's Rotation Changing? 372

Posted by Hemos
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."
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Is The Earth's Rotation Changing?

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  • well known (Score:5, Funny)

    by lovebyte (81275) <lovebyte2000NO@SPAMgmail.com> on Monday March 10, 2003 @10:18AM (#5476683) Homepage
    This has been known since 1951 [imdb.com].
    • since 1900 (Score:5, Insightful)

      by peter303 (12292) on Monday March 10, 2003 @10:37AM (#5476870)
      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.
    • by trotski (592530) on Monday March 10, 2003 @11:13AM (#5477162)
      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: [talkorigins.org]

      A flat earth, it's not just a good idea; it's the truth.
      • Simple (Score:3, Funny)

        by jabber01 (225154)
        The Earth rotates at the "and you turn yourself about" point, when the turtles do the Hokey Pokey.

      • 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.

        Obviously, you are not nearly up to the state of science in Earthism. Of course the world is both flat and round (think a round piece of cardboard). And it rotates around the earth axis, which is mouted under the temple rock in Jerusalem (you did know that the middle of the earth is in Jerusalem, right?).


        Now, in El Nino years, all the scientists move to South America to study the phenomenon. South America is on the outermost fringe of the flat world (as is North America), hence they move mass from near the center (Europe) to the fringe. So to maintain angular momentum, rate of rotation has to slow down.


        Now since this information is out, more scientists are going to study El Nino, of course, making the problem worth. And once the US scientists (being slightly slower and always behind) notice this and flock to Peru to, we can even expect the world topple over. If George Bush were slightly smarter, he would move troops to South Korea, to balance things. Moving them to Iraq helps with the rotation problem, but not with the toppling problem...

    • Yeah, but at least it's not a dupe. . .

  • by kaszeta (322161) <rich@kaszeta.org> on Monday March 10, 2003 @10:19AM (#5476691) Homepage
    The days are getting longer? Cool, I could use an extra five minutes each day to read Slashdot...
    • And I just thought that life was just getting more boring - no, the days ARE getting longer!
    • the Earth may slow ever so slightly because of stronger winds, increasing the length of a day by a fraction of a millisecond.

      Ill bet my bastard boss is gonna try and get that time outa me too!
    • Conservation of angular momentum.

      1. I stand up, it slows down.
      2. I sit down, it speeds up.
      3. I stand up, lift up my glass, it slows down.
      4. I pour a beer, beer goes down into glass, Earth speeds up.
      5. I lift beer to mouth, Earth slows down.
      6. I drink beer, beer goes down gullet, Earth speeds up.
      7. I drink much more beer, previous steps repeat.
      8. I drink too much beer, I fall down. Earth rotation speeds up. Earth now spinning very, very fast. It must have been a long way down.
  • by Txurlo (555886)
    Maybe it's because of all the people holding their breath over the PS3 coming out this year?
  • Beans! (Score:2, Funny)

    by skaffen42 (579313)
    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

    And I thought the day only felt longer after eating at a Mexican restaurant.

    • Re:Beans! (Score:2, Funny)

      by rabiteman (585341)
      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

      And I thought the day only felt longer after eating at a Mexican restaurant.

      I think it's clear that the real culprit is windmills. If wind pushing on the Earth makes its rotation slow down, it logically follows that the more surface area to be pushed on, the greater the effect, whether or not you eat Mexican food. This means that those giant canvas sails on windmills aren't just grinding grain for Dutchmen in their clogs, they're lengthening the day! I've seen many other posts here lauding the extended day for a variety of reasons, but a longer day is simply no good, as Sealab 2021 is already shown on TV far too infrequently, and those fractions of a millisecond add up over the course of a week! Our only possible course of action: demolish all windmills, so we can see our delicious animation seven fractions of a millisecond sooner every week. Yup, no choice but to destroy all windmills... and that damn Sydney opera house.

  • SUPERMAN! (Score:5, Funny)

    by Acidic_Diarrhea (641390) on Monday March 10, 2003 @10:20AM (#5476700) Homepage Journal
    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.
    • Well, I think you miss the point of the article. Maybe you should read it first next time.

      What they're saying is that now, we don't NEED a mythical being like superman to accomplish time travel. Now, we can just release some really fucked up greenhouse gasses and eventually mess with air currents enough that time travel will be easy and real.

      I wouldn't buy my voodoo 3 either.
    • haha voodoo 3.

      I would buy all of microsofts stock, do a nasty hostile takeover, and then bankrupt it

      Just to stop the the terminator-like future which comes as a result of the current microsoft
      • I would just go back to Bill Gates' first chance encounter with an electronic calculator and exchange it for a Matchbox car so he grows up to be a gas station attendant or Nascar technician.

  • Oh great, (Score:2, Insightful)

    by Quila (201335)
    Yet another thing the greens can attach to (supposedly man-made) global warming.
    • by stinky wizzleteats (552063) on Monday March 10, 2003 @10:29AM (#5476808) Homepage Journal

      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.

      • by Anonymous Coward
        But given a random distribution on the direction of movement of all the SUVs, it'd balance itself out.

        I mean if 25% are going due north, 25% due south, 25% east, 25% west then the net effect would be 0.

        I'm more worried that people in North America are getting fatter, making the earth lopsided. So far it's just USA and Canada putting on the weight. Luckily those earth-conscious Mexicans are starving themselves to counter the effect.
    • Re:Oh great, (Score:2, Flamebait)

      Oh no! Scientific experiments revealing the truth! The horror of having to deal with the consequences of spitting toxic shit at unnatural rates into the air for centuries! Let's burn their textbooks, lest they try to save the environment!
      • by Quila (201335) on Monday March 10, 2003 @10:52AM (#5476982)
        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?
        • by gowen (141411)
          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?
          You did think that. Allow me to correct your (extremely popular) misconception. http://www.wmc.care4free.net/sci/iceage/ Executive Summary : No peer reviewed journal printed a single paper predicting an anthropmorphic global iceage. Not one. Anywhere. Really.
  • by Anonymous Coward on Monday March 10, 2003 @10:20AM (#5476705)
    this is really just a fake news to hype up "The Core", isn't it?
  • ...since the poles flip/shift every few million years, it should be no surprise that rotation would suffer in the mean time.

    By the way...when is the next pole shift due?
    • by Jugalator (259273) on Monday March 10, 2003 @10:35AM (#5476845) Journal
      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 [poleshiftprepare.com] either, complete with pictures of his Survival Tents. This sure is stuff for Something Awful [somethingawful.com]. =)
  • Superman? (Score:3, Funny)

    by sporty (27564) on Monday March 10, 2003 @10:22AM (#5476717) Homepage
    Just so long as it doesn't start spinning backwards. I dont' feel like going through my childhood again, especially not in reverse.
  • This is news? (Score:2, Insightful)

    by hottoh (540941)
    Physics tells me that a gas and a fluid have many similar characteristics. The most significant difference of course is a liquid is approximately 1000 times more dense than a the atmosphere.

    Consequently the oceans slow the rotational period of the earth. I read about the physics of the tides twenty some years ago. The physics was clear then.

  • I thought my work week was getting longer...
  • by BongoBonga (317728) on Monday March 10, 2003 @10:22AM (#5476727)

    It seems like a reasonable enough argument that the rotation period of the earth would change during an el nino period. But once this the el nino effect had ended the rotation of the earth would have to return to normal, so any effect that might occur would be only short term. Also due to the large difference in the mass of the solid earth and the earths atmosphere, the change in the earths period of rotaion would be so small as to be unmeasurable and therefore unimportant.
  • by LittleGuy (267282) on Monday March 10, 2003 @10:23AM (#5476730)
    Shuttle crashing, earth's rotation affected....

    When did life turn into a Hilary Swank action flick? [imdb.com]
  • by BabyDave (575083) on Monday March 10, 2003 @10:23AM (#5476740)

    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

    • OK, so don't slow down...
    • Well, actually we all need to run WEST if we want to speed the Earth up a little. And it would work, just not as well as some giant rocket engine (think cartoon villian plots sized giant rocket). You work on running, I'll build the rocket.
    • 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.
      • Well, let's see. If you run one way and then run back, you're cancelling out your effect. Except, if you run one way and then puke, when you run back you're exerting less force. So that's good so far.

        If you run one way and have a heart attack, you're still fine as long as they don't bury you back where you started.

        Getting bored and going home is bad though unless you start by going the wrong way, and then pick up a big juicy burger before oozing back.

        So really, I think there's enormous potential in the /. crowd. Typically little kinetic, but good potential...
    • by pclminion (145572) on Monday March 10, 2003 @11:45AM (#5477432)
      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.

  • Old news? (Score:4, Interesting)

    by AuraSeer (409950) on Monday March 10, 2003 @10:24AM (#5476753)
    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.
  • by OldAndSlow (528779) on Monday March 10, 2003 @10:24AM (#5476756)
    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.
    • by tbmaddux (145207) on Monday March 10, 2003 @10:52AM (#5476981) Homepage Journal
      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, [slashdot.org] 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.

      • Momentum isn't energy, and is conserved by itself. In fact, the numeric value of momentum depends entirely on the reference frame, and therefore can't tend towards zero due to non-conservative forces, because there's no zero, since there's no absolute reference frame.

        There are two ways the earth's rotation can change: keep the same angular momentum by moving mass away from the axis, and throwing mass out into space with a more easterly velocity than it would have sitting where it started.

        The study mentioned in the article isn't talking about a non-conservative change in the Earth's rotation, in any case, but rather a conservative change due to permanent (or, at least, long-term) climate change. If the winds blow harder, the Earth slows down; if the winds blow less hard, the Earth speeds up. If the winds continue to blow hard for the next millenium, it'll be a long millenium.
    • by pclminion (145572) on Monday March 10, 2003 @10:59AM (#5477046)
      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.

      • No. Angular momentum is conserved. Rotational energy is not necessarily conserved -- if you heat up the Earth, the athmosphere will expand, the earth's rotation will slow down, and the total rotational energy will increase -- but the angular momentum remains constant.

        That is, it remains constant in a closed system. The only long-term changes to the earth's rotation come from the earth's angular momentum being transferred to the moon.
        • Rotational energy is not necessarily conserved

          I didn't say it was. I said *total* energy is conserved. This includes heat.

          if you heat up the Earth, the athmosphere will expand, the earth's rotation will slow down, and the total rotational energy will increase -- but the angular momentum remains constant.

          The effect they're talking about isn't due to increased rotational inertia from an expanding atmosphere. They are talking about fast winds exerting friction on the surface. You're correct in that the angular momentum transferred from the Earth ultimately ends up in the atmosphere, but the point I was making is that this transfer is not reversible. The angular momentum appears in the atmosphere as heat, and all the well-known efficiency theorems from thermodynamics apply to it.

    • You've got your basic laws of thermodynamics down pat, my friend, but you're forgetting one thing. Conservation of energy is true in any closed system, but the winds of the Earth are fueled by sunlight. That means the energy comes in as heat, then turns into kinetic energy, so it would actually be possible for the effect to change the speed of the earth's rotation.

      Now, why milliseconds a year are important? I couldn't tell you; if this effect got bad enough to have a noticeable impact on any of us, the planet would be uninhabitable. It would take a lot of wind to speed up a planet.

      Let's pay attention to the important news here, people. Like, will Sony ship a reasonable number of PS3s?

      ~SL
  • by silvaran (214334) on Monday March 10, 2003 @10:31AM (#5476817)
    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?
    • I hope you live in the southern hemisphere because the earth is actually closer to the sun during the winter in the nothern hemisphere.
    • by Ctrl-Z (28806) <tim@timcolTEAeman.com minus caffeine> on Monday March 10, 2003 @11:03AM (#5477079) Homepage Journal
      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?

      Are you referring to leap seconds [navy.mil]?
    • The bulshit detector almost reached full-scale. Note that in the winter the earth is not farther away from the sun as you think, but one hemisphere gets lower/higher sun path because of the inclination of earth's rotation axis.

      For all that matter to our daily lives, earth's rotation is a almost round circle, that is, we don't get close/far away from the sun.
      • The earth revolves around the sun in an elipse. It's close to being a circle, but not quite. In the northern hemisphere, during the winter, the earth is actually at it's closest distance from the sun. In summer, it's further away. In the southern hemisphere the opposite is true.

        What causes seasons is not distance from the sun. It is length of day and angle (and consequently concentration) of the suns rays on the surface. In winter time, the northern hemisphere is tilted away from the sun, therefore receiving more indirect rays. During the same time, the southern hemisphere is tilted towards the sun, making the rays hitting the surface more direct and concentrated.

        Remember that when you are experiencing winter, the other half of the earth is experiencing summer.
    • by pclminion (145572) on Monday March 10, 2003 @11:38AM (#5477376)
      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).

    • You're thinking of leap seconds, which are used to synchronize the time of day with the number of seconds elapsed. These get applied to the readouts of atomic clocks, and the time gets distributed from there.
  • In what way is this a "warning". I can't think of any ill effects which could occur as a result of a day taking a few milliseconds longer.

    I'd say its more of a "curiosity".
  • by little1973 (467075) on Monday March 10, 2003 @10:34AM (#5476838)
    ...due to the Moon and the Sun. On one day the rotation of the Earth will stop and as we only see one side of the Moon, only one side of the Earth will face the Sun. Once I calculated the time when the rotation will stop and I got about 5 billion years (assuming a linear slowdown). It's quite strange because that's about the remaining life of the Sun, too.
  • by goombah99 (560566) on Monday March 10, 2003 @10:39AM (#5476881)
    This smells a lot like a planted science article advertising the movie The Core [thecoremovie.com] ( 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 [slashdot.org]

    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.

  • by alnapp (321260) on Monday March 10, 2003 @10:39AM (#5476885) Homepage
    and other climatic changes certainly make the day seem longer
  • Main topic. (Score:4, Insightful)

    by Fastlane (449058) on Monday March 10, 2003 @10:42AM (#5476912)
    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.
    • 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.

      I don't think the conservation argument applies, because the Earth is not a closed thermodynamic system. There is energy coming in from the Sun. If that energy is converted into ocean currents that cancel each other out all well and good, but if the currents start to flow more westwards than eastwards or vice versa, then the rotation can be affected in such a way that there's no guarantee that it will be reset.
  • Is the climate changes of el Niño slowing down the earth, or is the slowing down of the earth the origin of el Niño? Or maybe have both the same common cause?

    If you two related things don't mean that the first named is the cause and the second one the effect, even if in theory one could make some impact in the other.

  • by Spacelord (27899) on Monday March 10, 2003 @10:43AM (#5476921)
    Okay ... so the days are getting longer, but what I want to know is: does this mean that I get to sleep a bit longer every night or do I have to work a bit longer every day??
  • by RamsÚs Morales (13327) on Monday March 10, 2003 @10:45AM (#5476932)
    If I recall correctly, earth rotation, in the beginning, was just 12 hours, and it's been slowing down mainly due to the tides.
  • 1. The rotation of the Earth decays slowly because of interaction with the moon, i.e. the friction of the tides.

    2. The interaction between Earth (solid ground plus oceans) and atmosphere can only exchange each participant's orbital momentum; it does not change the total orbital momentum.

    3. Therefore, large-scale atmospheric phenomena can accelerate/decelerate the rotation of the earth on slow timescales (months/years). They have no influence on the long-scale deceleration (cf. point 1). The main point of the article is that one can use this short-time correlation as a test of measurements of the atmosphere and numerics: The fact that the two vastly different systems, namely the meteorological and the astronomical, are in good agreement according to the conservation of angular momentum gives us assurance that both these types of measurements must be accurate.

  • What about wobble? (Score:2, Interesting)

    by prestidigital (341064)
    Some months ago I saw an episode of NOVA which postulated that the moon has been gradually drifting out of Earth's orbit for many hundreds (thousands? millions?) of years. This causes the Earth's spin to be less uniform, to wobble. The more drastic the wobble, the more extreme are the changes in weather. I haven't seen anything else on this since, so perhaps it is not a theory that holds much credibility with scientists. On the surface, it seems to make sense.
  • by JoeRobe (207552) on Monday March 10, 2003 @10:53AM (#5476997) Homepage
    First, I'm curious (maybe someone out there has a link?) about how solar wind affects affects day lengths. It's known and been imaged that bursts of solar wind cause the earth's atmosphere to swell, and I'm curious what this redustribution of mass does to the moment of inertia and rotational speed of the planet.

    Second, I find it kind of interesting the change in the way we percieve time. Centuries ago, the earth made a great clock. 24 hours was defined as a day, and if all of the sudden the day became longer, that longer period of time was defined as 24 hours. Now, we see that the earth makes a pretty bad clock (by today's standards), and rather than relying on the earth as our ultimate timepiece, we rely on atomic clocks. It seems strange: we have all of these time units like hours, days, months, years, etc., all defined first by astronomical methods, but now because of our (technological) ability to be more regular than the cosmos, the hour, day, month, year, etc. have sort of lost their origins.
    • Yes, we still rely on those old and arbitrary divisions. But you know what? There /is/ a reason we kept them: they're good. An hour is a good amount of time to wait for something to happen. You could give or take a few minutes off of it, but an Hour really is a good length- much shorter, and you wouldnt be waiting long enough, much longer and you dont want to wait so long [for example, /three/ hours]

      See, these original divisions are based loosely on astronomy, sure. But it was /man/ who decided how much to divide up.

      People who want to use a decimal-based system for dividing time are morons.

      Obviously the above post is phrased quite poorly, but I do hope that I managed to get my point accross.
  • all orbits have to have their own irregularities, I mean there's all kinds of gravitational fields that act on the the earth. not to say that the scientists are totally full of shit, but I'd say that it's a lot more likely that the rotation and orbit is changing the weather than weather changing the planet.
  • Doesn't sound very impressive. If the change progressed much faster and the day got say, 1 minute longer in 10 years, would we notice anything?
  • Great (Score:2, Funny)

    More time for me to work on my TPS reports.
    g
  • So if the earth's rotation has decreased, then there will be less centripetal motion acting to reduce the effects of gravity. That explains it. I thought I had just put on weight, glad to see there's a scientific explanation.
  • Oceans (Score:3, Interesting)

    by barakn (641218) on Monday March 10, 2003 @10:59AM (#5477041)
    The Earth's oblateness (as measured by changes in the gravity field) has been increasing since about 1997 [nasa.gov]. Speculation points to net movement of water from rapidly melting mountain and subpolar glaciers to the equator. One would suspect this would change the Earth's moment of inertia more than would changes in wind, but it is not mentioned in this most recent article.
  • The slowing rotation may also be affected by a change in the Earth's center of gravity. I recall from my calculus based physics class that if the mass of a rotating object is translated from near the center of rotation further away from that center of rotation, an object slows its rotation. This is known as conservatin of angular momentum. Taking all that crude oil from the ground and burning it in our cars over 100 years has shifted some the Earth's mass from below the surface to the atmosphere. And since there was a phase change in moving this material from the ground to the atmosphere, this should make the effect a little more noticable as the CO2 can be further displaced high in the atmosphere. This may contribute to a thousands of a second decrease in the Earth's rotation. Of course, I'm sure this guy also didn't take into account the umpteen million metric tonnes of star dust slamming into the Earth every year, adding mass to the Earth and further decreasing the rate of rotation.

    I don't know, I just a geeky chemist with wild ideas.
    • Earth weighs about 6 x 10^24 kg. We take about 4.5 x 10^12 liters of oil from a distance of 6,376,660, from the center of the Earth to about 6,378,160m from the center of the Earth (average oil well depth is roughly 1500m), that's .02% of the radius.

      Somebody please do the math of how that would affect angular momentum.
  • Don't fart in a general direction, fart West.
  • by Anonymous Coward on Monday March 10, 2003 @11:16AM (#5477190)
    Ok, everyone, all over the planet...

    Face east, and...

    BLOW...

    now face west and...

    SUCK
    ...and ... EAST ... BLOW! ... WEST ... SUCK! ... EAST...
  • At the top of the page in the radio.weblogs.com column:
    How new technologies are modifying our way of life
    I never new the El Nino was a new technology ;-)
  • by slipstick (579587)
    These guys seem to have forgotten that scientific data has two requirements. Accuracy and precision. Since they refuse to show the precision of their measurements, any statement as to their accuracy is right out the window.

    Give us those error bars guys, than we can talk.

  • Root Cause (Score:3, Funny)

    by scott1853 (194884) on Monday March 10, 2003 @11:21AM (#5477225)
    El Nino isn't the root cause of the problem. It's that damn butterfly over in China again that's causing El Nino.
  • hmm.. (Score:2, Insightful)

    by C21 (643569)
    for that matter what about the minute changes that our orbit undergoes when we acquire more space dust (pounds and pounds a day) or send people/spacecraft into space. Losing or gaining mass effects orbit, too, in addition to meterological events.
  • by at10u8 (179705) on Monday March 10, 2003 @11:28AM (#5477287)
    The fact that the earth's rotation is slowing down has been known for most of a century. That its speed varies seasonally has been known since the 1930s. That the speed varies daily under the influence of the winds and tides has been known since the 1980s. That its speed varies daily due to the oblateness of the solid inner core has been known since the 1990s. That its speed varies on a timetable of decades under the influence of core/mantle currents is still being measured.

    All of these measurements are made under the purview of the International Earth Rotation Service [iers.org]. There are models for all manner of astrophysical and geophysical effects considered in the Conventions [navy.mil] that are used when reducing the data.

    The way that solar noon is kept at civil time noon is by inserting leap seconds. In most places civil time is offset directly from UTC [iers.org]. When a leap second is inserted the day is 86401 seconds long.

    This irregularity upsets some kinds of timekeeping systems, and as a result there has been discussion that leap seconds should be abolished. That would cause noon to drift away from noon. That may not be a good thing [noao.edu].

  • by Vietomatic (520138) on Monday March 10, 2003 @11:35AM (#5477348)
    Another important factor that contributes to the slowing down of Earth's rotation is definitely space dust. Every year, the Earth gains at least 30 million kilograms of space dust. This added mass will indeed reduce the time it takes for the Earth to complete a rotation by fraction of a second.

    We need a space vacuum to suck up all of the dust before it gets here...wait a minute, space is already a vacuum!
  • Every week (Score:5, Funny)

    by rgf71 (448062) on Monday March 10, 2003 @11:37AM (#5477362) Journal
    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.
  • People need to realize that there is no such thing as a constant when we are talking about planetary physics.

    Ice age(s) anyone?
  • Rotational speed matters not.

    Consider precession [cornell.edu], where the Earth's north axis slowly moves along the celestral plane like a slowing top, which changes what star we consider to be our "North Star." I believe Vega was closer to being the North Star some 15,000 years ago.

    A more dire event: When the magnetic poles shift or trade places. That probably wasn't an event way back when except for migratory animals, but today with all of our electronics, it could be interesting to see what effect a shift would do to a computer or compass.

    Or, maybe we should worry more about the Mets or the Cubs. Or if our martinis were shaken and not stirred...
  • by Dr. Zowie (109983) <slashdot@@@deforest...org> on Monday March 10, 2003 @12:04PM (#5477579)
    The day is slowing down because of tidal drag from the Moon. Tides stretch the Earth along the Earth-Moon line; the Earth's rotation drags the axis of stretch around (about 45 degrees away from the Earth-Moon line, if I remember right). The asymmetrical shape pulls the Moon forward a little in its orbit, and the equal-and-opposite reaction (remember Newton's 3rd law?) slows down the Earth's spin by the same amount.

    The Moon was certainly closer at one time -- Robin Canup, who works down the hall from me, has done some fabulous simulations of the formation of the Moon (thought to be from a giant impact of two planetoids; the larger fragment evolved into the Earth, while the smaller one became the Moon). She claims that Moon must have formed right around the Roche limit (the distance at which it would just barely not be pulled apart by tides). If that's so, then it would have had an orbital period of about 6 hours. Meanwhile, the Earth would have been rotating faster yet.

    The ongoing tidal drag is evident in the "leap seconds" that some international committee periodically adds to atomic time to get coordinated universal time. The leap seconds are becoming more frequent, because (surprise) the day is slowing down a microscopic but measurable amount compared to its speed in 1951. (One leap second per three years corresponds to a proportional change of only 1 in 10^8 [100,000,000], so no wisecracks about sleeping in late, please!
  • ... that time is defined by the vibrations of a cesium atom [eu.com] instead of being just a certain fraction of a day.
  • Yeah, well... (Score:4, Interesting)

    by jd (1658) <imipak@nOSPam.yahoo.com> on Monday March 10, 2003 @12:30PM (#5477792) Homepage Journal
    Tomorrow: NASA discovers Navier-Stokes Equation!


    Sadly, the fact that gasses (identically to liquids) can create drag on any body within them is far from new, startling or amazing.


    In fact, here are a few other trivial points:

    • Off-axis volcanic eruptions will also alter the Earth's spin, by some miniscule amount, by acting as a simple rocket.
    • The tides alter the centre of mass and centre of gravity, so ergo must continuously vary the Earth's rotation.
    • In winter, the mean radius is lower than that in summer (because of the loss of a lot of vegetation). Because angular momentum is preserved, winter days must really be shorter than summer days (where the mean radius is greater).


    None of this stuff is outside the scope of an A-level student taking maths and physics. The chances are, though, they won't get 5-figure paychecks for coming up with such trivia.

  • by Junior J. Junior III (192702) on Monday March 10, 2003 @12:37PM (#5477847) Homepage
    is to attach giant rocket engines to the side of the planet, facing due west and due east. We can fire them periodically to recalibrate the length of our days. Then the environment will be safe!
  • by mangu (126918) on Monday March 10, 2003 @01:30PM (#5478310)
    Have you ever worried about who is responsible for making sure the Earth is rotating? Check the International Earth Rotation Service [iers.org] website.
  • by jonadab (583620) on Monday March 10, 2003 @04:52PM (#5480095) Homepage Journal
    Sheesh, this is NEWS? The earth is an open system: that's been
    established _repeatedly_ now. The energy coming in from the Sun
    (and trace amounts from other sources) is not without effect, duh.
    So of _course_ stuff changes. Yeah, the earth's rotation changes,
    its inclination to the eccliptic changes, it's orbit changes, its
    mass changes, the distance to the moon changes, the composition
    of the atmosphere changes, the chemical content of any given
    rock changes, et cetera. Uniformitarianism is an interesting
    idea, but it doesn't jive with the real world.

    Next they'll be reporting that the English language changes too...

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