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Thread: Precession confusion

  1. #1
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    Default Precession confusion



    Lately I've been trying to get a handle on precession of the equinoxes but I'm finding it a little tricky to understand. Is it due to a rotation of earth's rotation axis or is there something else involved? Maybe the something else is actually different precession by a different name. As you can see I'm just a little confused.
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    Default Re: Precession confusion

    I'll try to clarify the question. Something causes a change in which star is our north star. Right now it is Polaris. Over time that will change. Is that due to precession and what type of precession is that? Another thing that happens is that perihelion, I believe, will change seasons over time. Right now it is in January but will change over time. Is this another type of precession?

    Am I asking too much?
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    Default Re: Precession confusion

    From my understanding, earths rotation has a slight 'wobble' to it so over time the 'north star' will change. Someone else smarter than I will have to chime in for more details (or any corrections in my statement).

    https://en.wikipedia.org/wiki/Precession
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    Default Re: Precession confusion

    This explains it fairly well. Right omeek, It wobbles on its axis (23.5*) every 26 000 years
    https://www.youtube.com/watch?v=0qHjtp4cdCA
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    Default Re: Precession confusion

    Yeah I get that part. That's what I meant by the rotation of earth's rotation axis but the other thing is the change in perihelion over time. I think that's some kind of precession also.
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    Default Re: Precession confusion

    The Earths orbit is an ellipse. The perihelion and aphelion shift sligntly each year. Think of a spirograph....
    It's called Apsidal precession

    https://en.wikipedia.org/wiki/Milank....6_smaller.gif

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    Default Re: Precession confusion

    ... and yes, the precession of the perihelion point of the Earth's orbit is different from the precession of the Earth's axis/equinox.
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    Default Re: Precession confusion

    Ahhh. Apsidal precession. That helps. I just couldn't see how axial precession could have the effect of changing the season of perihelion. Hence, confusion.
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    Default Re: Precession confusion

    certainly the orbit has a slight mismatch and the northern star will change position over time

 

 

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