Notices
Results 1 to 21 of 21

Thread: Why does the Earth keep spinning?

  1. #1 Why does the Earth keep spinning? 
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    I am no scientist and thoughts are my own, please be gentle!

    For 4.5 Billion years our planet has been spinning, that is perpetual motion in my book.
    What i cannot understand is, yes it's in frictionless space but it has gravitational forces pulling at it in the shape of our moon, causing Trillions of tons of water to be displaced every second, its also pulling at Earth's molten core. I thought this would be a huge damping effect.

    To do this for 4.5 billion years with only a very small loss seems incredible.

    The whole crux of my thoughts were
    1. The Earth has been spinning for an awfully long time, thats a long time for anything to spin!
    2. What factors are retarding the earths spin and can these be quantified?
    3. Do the quantified factors add up to expected losses of spin over the Earths history.
    4. Is there another force present assisting spin?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,517
    There hasnt been a small lose 0.005 seconds per year per year (which means that 4.6 billion years ago the earth was almost spinning twice as fast as it is now) so it has been losing energy.

    The spin of the earth is quite complicated (even the winds effect it to a degree) so im not sure that we know about all the things that have an effect on it.


    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  4. #3  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    Sorry river_rat, i know i'm new here and all but i've just done the basic maths with your quoted figures and the don't add up!
    5 mS x 4.6Ga = 23Ms
    23 Ms / 60 = 383333.3 Mins
    38333.3 / 60 = 6388.8 Hours retardation in spin[/code]
    I have no 'box' to think out of!
    Reply With Quote  
     

  5. #4  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    told you i was new here, let me try that again


    Sorry river_rat, i know i'm new here and all but i've just done the basic maths with your quoted figures and the don't add up!
    5 mS x 4.6GYa = 23Ms
    23 MS / 60 = 383333.3 Mins
    38333.3 / 60 = 6388.8 Hours retardation in spin

    assuming linear slowdown
    I have no 'box' to think out of!
    Reply With Quote  
     

  6. #5  
    Forum Bachelors Degree The P-manator's Avatar
    Join Date
    Nov 2005
    Location
    Toronto
    Posts
    474
    Hehe, that is a problem. When figures don't add up bad things happen. If someone messed up, we could all believe that tomorrow Earth will stop spinning.
    Pierre

    Fight for our environment and our habitat at www.wearesmartpeople.com.
    Reply With Quote  
     

  7. #6  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,517
    Quote Originally Posted by tuggyman
    told you i was new here, let me try that again


    Sorry river_rat, i know i'm new here and all but i've just done the basic maths with your quoted figures and the don't add up!
    5 mS x 4.6GYa = 23Ms
    23 MS / 60 = 383333.3 Mins
    38333.3 / 60 = 6388.8 Hours retardation in spin

    assuming linear slowdown
    Um how do you get that answer if i tell you the rate as 0.005 seconds per year per year?

    The correct math is 0.005s * 4.6 billion years = 266 days/year (so we have lost 266 days in our year compared to then). So a year then had 631 days which means that the days were 57% of the length they are now.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  8. #7  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    By the fact you said "if i tell you the rate as 0.005 seconds per year per year" that's pretty linear to me"!

    the reason i said "assuming linear slowdown" is due to other factors ie. moons orbit was closer having greater effect on tidal gravity etc
    I have no 'box' to think out of!
    Reply With Quote  
     

  9. #8  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,517
    Quote Originally Posted by tuggyman
    By the fact you said "if i tell you the rate as 0.005 seconds per year per year" that's pretty linear to me"!

    the reason i said "assuming linear slowdown" is due to other factors ie. moons orbit was closer having greater effect on tidal gravity etc
    Do you agree that the numbers add up though?
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  10. #9  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    sorry you are quite correct, i am new
    i think im going to be an observer from now on, i realise my place in the great scale of things
    I have no 'box' to think out of!
    Reply With Quote  
     

  11. #10  
    Forum Professor river_rat's Avatar
    Join Date
    Jun 2006
    Location
    South Africa
    Posts
    1,517
    Quote Originally Posted by tuggyman
    sorry you are quite correct, i am new
    i think im going to be an observer from now on, i realise my place in the great scale of things
    Dont observe - feel free to comment and if the need be there to rant. We all make silly mistakes here, and no one can claim to have all the answers.
    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
    Reply With Quote  
     

  12. #11  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    i'm going to crawl under my metaphorical box!!
    I have no 'box' to think out of!
    Reply With Quote  
     

  13. #12  
    Forum Professor captaincaveman's Avatar
    Join Date
    Jul 2006
    Posts
    1,355
    Isn't it right also, that as the earth slows the magnetic field around it will slowly weaken as well, something to do with the inner and outer core?
    CAPTAINCAVEMAN


    I ANSWER TO NO-ONE - The wonders of athiesm

    that which does not kill us only postpones the inevitable
    Reply With Quote  
     

  14. #13  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    What the hell, lets go out in style

    Is there another force present assisting spin?


    Here a thought (just a thought)
    The planet spins on it axis and produces a giant gyroscope. The Earth is also in a rotational orbit around the sun, could this angular movement of the orbit impart more rotational spin in our planet?

    I suppose it a bit like the bicycle wheel experiment whilst sittng on a swivel chair but in reverse.

    Im now holding my breath and closing one eye with both hands in my ears inside my metaphorical box!!
    I have no 'box' to think out of!
    Reply With Quote  
     

  15. #14  
    Guest
    If you type 'why is the earth slowing down' into google you will get a whole list of sites explaining the reasons.

    It seems it's mostly to do with the moon...
    Reply With Quote  
     

  16. #15  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    Thank you 'billco'.
    Is that a polite way of not even having to answer my last question because its too riduculas.

    Thats it i've blocked up the air holes, put on large sticker on my 'box' saying "pork products" and posted myself to Iraq.
    I have no 'box' to think out of!
    Reply With Quote  
     

  17. #16  
    Forum Bachelors Degree
    Join Date
    May 2005
    Location
    London, England
    Posts
    405
    tuggyman, stop being so pathetic. And don't reply to this with a "Oh, no, I'm so stupid I'm going to hide away at the bottom of the ocean." It's getting very tiresome. Contribute, ask questions, or just stop posting. It's entirely up to you.

    The spinning of the Earth is not "perpetual motion" in the sense that you can't get any energy out of it without stopping the Earth moving. Perpetual Motion refers to machines that carry on moving although driving some other force which would ordinarily drain the energy - which is impossible of course.

    Likewise, the gravitational force which keeps the Earth orbiting the Sun does not count as perpetual motion either. I can't remember the book that claimed that all science was wrong because something could move forever if you drilled a hole through the centre of the earth, but that was entirely based on the same misconception.
    "It is comparatively easy to make clever guesses; indeed there are theorems, like 'Goldbach's Theorem' which have never been proved and which any fool could have guessed." G.H. Hardy, Fourier Series, 1943
    Reply With Quote  
     

  18. #17  
    Forum Professor captaincaveman's Avatar
    Join Date
    Jul 2006
    Posts
    1,355
    can anyone verify my statement or did i just imagine it, the one about as the earth slows the magnetic field weakens cause of something to do with the reaction of the inner and outer core
    CAPTAINCAVEMAN


    I ANSWER TO NO-ONE - The wonders of athiesm

    that which does not kill us only postpones the inevitable
    Reply With Quote  
     

  19. #18  
    Forum Freshman
    Join Date
    Sep 2006
    Location
    England
    Posts
    9
    silas : Quote "It's getting very tiresome. Contribute, ask questions, or just stop posting."
    I was not being pathetic the whiskey did not help!
    It was a i think good atempt of being humorous, even now i've reread and sobered up, i laughed again!

    Stop pontificating, and lighten up a bit, have drink, get a girl etc.

    Thank you for the rest of your reply about perpetual motion though.[/quote]
    I have no 'box' to think out of!
    Reply With Quote  
     

  20. #19  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,168
    Quote Originally Posted by captaincaveman
    can anyone verify my statement or did i just imagine it, the one about as the earth slows the magnetic field weakens cause of something to do with the reaction of the inner and outer core
    The Earth's magnetic field is generated by fluid motion in the outer, liquid, core. The conventional explanation for the field sees tt is a self exciting dynamo. The strength of the generated field is dependent, in part, on the rotation of the Earth. Logically, a reduction in the Earth's rotational speed would tend to reduce the magnitude of the magnetic field.
    Reply With Quote  
     

  21. #20 torque 
    New Member
    Join Date
    Jul 2006
    Location
    INDIA
    Posts
    3
    A\Q ME EARTH ROTATES DUE TO THE TORQUE EFFECT OF SUN
    Reply With Quote  
     

  22. #21  
    Forum Isotope Zelos's Avatar
    Join Date
    Jun 2006
    Posts
    2,755
    earth keeps rotating since it once started rotate and allways will rotate
    There is no frame where earth will not rotate. It will slowdown but it wont stop
    I am zelos. Destroyer of planets, exterminator of life, conquerer of worlds. I have come to rule this uiniverse. And there is nothing u pathetic biengs can do to stop me

    On the eighth day Zelos said: 'Let there be darkness,' and the light was never again seen.

    The king of posting
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •