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I Eclipse path question

  1. Aug 21, 2017 #1
    Hi there,

    I've watched this video: . I have been curious the whole day why the eclipse path seems to be curved and obviously in our latitude. Is it because of both the moon's orbital plane and the tilt of the earth's axis? If it went across the US, that is a lot more than 5 degrees (moon incline) so I was just wondering about the geometry. I've done some research and that video was the best I found.
  2. jcsd
  3. Aug 21, 2017 #2


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    because the earth's surface is curved ! :smile:

    you are not a flat earther are you ? :wink:
  4. Aug 21, 2017 #3
    Absolutely not. I'm more asking about the north to south direction. I'm also asking about latitude. The video itself goes into what I'm asking but I want to know why the location changes. I understand that the moon has its own orbit causing the zigzag shape. How NASA calculate the exact route? I understand what a geodesic is and I'm pretty sure that this is more complex. I'm not asking why it goes west to east either. That's based on the speed on the moon relative to earth. I'm asking why the latitude changes.
    Last edited: Aug 21, 2017
  5. Aug 21, 2017 #4

    jim mcnamara

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    @davenn humor is oblique sometimes, but we get posters on PF that have agendas that have little to do with Science. So I understand why he asked the question. No harm no foul.
  6. Aug 21, 2017 #5


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    I still stand by my first part

  7. Aug 21, 2017 #6
    I mean it's all making spherical representations on a piece of flat paper but I'd like to know the calculations. I'm maybe not 100% on geodesics but a helpful discussion would be welcomed! I guess I'm confused on why Oregon to Charleston. Is it because of great circles? It's the shortest distance between two points. If it followed the same latitude, it wouldn't make any sense?
    Last edited: Aug 21, 2017
  8. Aug 22, 2017 #7


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    If you neglect the rotation of Earth, the eclipse center follows a circle on a sphere. A great circle is only a special case of this. As seen from the Sun, the Moon crosses the Earth, where the circle has an angle somewhere between 18° and 28° relative to the equator as both the Earth's equator and the orbital plane of the Moon are not aligned with the orbital plane of Earth.
    The rotation of Earth makes things more complicated and leads to deviations from the simple circle. Its effect is larger when the shadow of the Moon is closer to the subsolar point, especially if it is at the equator, as the direction of the rotation is orthogonal to the Earth/Moon/Sun axis in this case.
  9. Aug 22, 2017 #8

    Ok this is what I thought. Thank you very much!
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