What if the Earth suddenly stop revolving around its axis?

Discussion in 'Physics & Math' started by Saint, Sep 4, 2017.

  1. Xelor Registered Member

    Messages:
    42
    AFAIK, the OP-er has not indicated that his/her question is to by responders be construed as a "thought experiment." (see below) Is there a convention that applies here on Sciforums (or in the Physics & Math subforum of it) whereby questions are automatically taken to be thought experiments?

    I love cats; I have five of them. LOL

    I read the OP and the OP-er's subsequent question just as you did....
    ...What element of of the OP indicates that readers are to construe the questions posed be so for the purpose of establishing a thought experiment? (https://plato.stanford.edu/entries/thought-experiment/)

    To wit, contrast the language of the OP with that found when reading the paper containing one of the archetypical thought experiments in modern physics. In section five of "The present situation in quantum mechanics" ("Die gegenwärtige Situation in der Quantenmechanik"), Schroedinger "officially" introduced the world to his "cat" by writing, "One can even set up quite ridiculous cases." [Translation --> Trimmer, Proceedings of the American Philosophical Society, 124, 323-38]

    One does not need any understanding of physics, math or anything other than English (German, if one reads the paper in its original language) to recognize that what follows that sentence, the scenario in which one ends up with Schroedinger's cat as both alive and dead, is a hypothetical situation the man presented to illustrate a point. In the text of the OP, one finds no indication that the OP presented his/her question as a "thought experiment." Moreover, insofar as there is no dearth of non-hypothetical discussion about the matter of what would happen if Earth suddenly stopped rotating about its axis, not the least of which includes the discussion published on NASA's website (that's the one for which I, in post 33, provided a hyperlink), absent some sort of phrase/clause/heading that indicates the OP-er's questions are indeed presented as a thought experiment, construing it thus as such but an instance of one's succumbing to counterfactual speculation.



    At the risk of seeming while not aiming to be pedantic, billvon, I strongly suspect you meant "gedankenexperiment." A "gendanken" is a member of Sciforums (http://www.sciforums.com/encyclopedia/Gendanken & http://www.sciforums.com/members/gendanken.9309/), and almost certainly not a thought experiment -- LOL -- though his/her parents may declare otherwise. One'd need to ask them to be sure. LOL

    I would never have known that "gendanken," rather than "gedankenexperiment," is anything at all; however, I am not aware that "gedankenexperiment" had been shortened and, in any case, "gedankenexperiment" is not a word that's so frequently used in "my word" (management consulting) that I didn't need to confirm its spelling and possible revision to "gedanken" to make sure what I thought you likely meant was indeed what you meant. Upon bothering to confirm whether the word I was aware of is spelled as you spelled it or whether "gendanken" was a spelling variant of "gedanken," I discovered the existence of "gendanken."

    Well, sure, "Gandalf." When "Glenda the Good Witch" waves her magic wand, whatever she wills can and does happen. LOL

    Forgive me for not recognizing that I find myself engaged in discourse with "LaPlace's Demon." LOL
     
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  3. river

    Messages:
    9,793
    Think of the moon , its gravity is 0.16 g . The moon still rotates . Without the astronaughts weight , they would have floated off the moon .

    So then if the Earth stopped revolving , if hopped , skipped and jumped , you would just drift off .
     
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  5. DaveC426913 Valued Senior Member

    Messages:
    7,243
    The OP asked what would happen if the Earth suddenly stopped spinning - and then in the same paragraph, asked about how that would affect gravity. I interpret that to mean the OP's interest is in clearing up their base confusion between the spinning Earth and gravity - and not so much in the confounding side effects of the real world.

    Granted, the OP's follow-up question was about whether we would be carried off into space.
     
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  7. timojin Valued Senior Member

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    At the high spin that we are going, is there a contribution of centrifugal forces ?
     
  8. river

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    9,793
    Of course .

    But size , or volume of Earth , minimizes the centrifugal force , to the point of being not experienced , by anything .
     
  9. Xelor Registered Member

    Messages:
    42
    I interpreted it as the OP was aware that his/her conception of such an event may be amiss and merely posed the question here to get an answer to it, perhaps not realizing that simply typing the question into Google's search field would provide an abundance of accurate answers.

    One would need to ask the OP-er why s/he chose to pose the question as s/he did and here rather than research the answer on his/her own. Unless and until s/he attests to deliberately intending to effect a thought experiment, I'm not buying that line. LOL To concur with that notion, particularly on the basis of some assumed/implied, as you put it, "magic" is to open the door of physics and math to all manners of absurd notions that don't presently merit exploration under even the rightly and deliberately intellectually-liberal auspices of theoretical physics and mathematics conjecture.
     
  10. river

    Messages:
    9,793
    Yet the question is valid .

    If the Earth did stop rotating , gravity on Earth would be minimized . Gravity is a very , very , very , weak force .

    As I said , the moon rotational force is a good example .
     
  11. origin Trump is the best argument against a democracy. Valued Senior Member

    Messages:
    9,998
    It looks like that would be about 0.3% at the equator. So the centrifugal force would make a 100 kg person weigh 300 gm less.
     
  12. RADII Registered Member

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    97
    And causes Venus to spin clockwise (opposite all the other planets).
     
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  13. river

    Messages:
    9,793

    Does this make sense to you , origin ?
     
  14. Janus58 Valued Senior Member

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    1,811
    Earth's angular speed (w) 7.29e-5 rad/sec
    Radius at equator(r) 6378000 m

    Centripetal acceleration = w^2*r = .0339 m/s^2
    Acceleration due to gravity 9.8 m/s^2
    .0339/9.8 =~ .0034 = 0.34%

    .0034*100kg = 0.340 kg = 340 g.

    Depending on how accurate you want to be, 300 g is a "in the ballpark" figure.
     
  15. Janus58 Valued Senior Member

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    1,811
    I wouldn't exactly call one rotation per 24 hrs (7.29e-5 rad/sec)a high rate of spin.
     
  16. river

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    Thats not my point , it doesn't matter .
     
  17. DaveC426913 Valued Senior Member

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    What? What do you mean by minimized? Are you suggesting that if I were standing on a non-rotating Earth I would weigh significantly less than I do now?
    How do you rationalize this?
     
  18. DaveC426913 Valued Senior Member

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    Yes - the confusion was about gravity. The OP specifically pointed that out.
     
  19. river

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    Yes

    Well the Moon gives a hint .
     
  20. DaveC426913 Valued Senior Member

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    Don't be coy; defend this.

    By what method do you assert that decreasing rotation to zero reduces gravity?
     
  21. river

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    Being coy ?

    I was merely trying to get anybody to think of the moon of an example of gravity through the rotation of a solar body .

    Look think about it , stop thinking about the messenger , and think upon the idea .
     
  22. DaveC426913 Valued Senior Member

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    Yes. Don't hint. If you have something to say, please say it.

    I'm asking you to explain it. How do you think rotation affects gravity? And how does the Moon play into this?
     
  23. river

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    9,793
    Rotation is a force , notice that gravity in scifi is based on rotation . 2001 does this etc.

    The moon gives an example where rotation matters .
    "Weight" is a measure of that gravitational pull. ... The Moon's mass is about 1.2% of theEarth's mass (1/80th), so the Moon's gravity is much less than the Earth's gravity: 83.3% (or 5/6) less to be exact. Other related facts: the Moon is 1/4 the size of the Earth by diameter, and 1/50 the size by volume.

    But try to find the comparison between the Earths rotation and the moons rotation . Can't find it .
     

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