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Thread: Declination of planet Earth

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  1. #1
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    Declination of planet Earth

    Has this changed in the past 7-8 months?

    I only ask because for 23 years (more than two solar cycles) the Sun has risen over the island in the middle of the lake I live on and come beaming in through the S.E. facing window. Summer to Winter would see it move a few degrees left and right, meaning I would see it rise directly over the island during Summer months and a little to the left of the island during the Winter.
    Considering I live in CT, not far South of that 45* latitude, I would anticipate a reasonable swing in location of sunrise, but expect it to stay within about 15* of arc.

    This year, however, since the Winter Solstice the Sun has not reversed its travel and continues to rise further and farther to the left instead of returning to it's Summer point. Where the Sun always rose directly in front of the house it is now rising on the left side of the house. This mean I'm viewing the sun rise almost North East from my location.

    Sunset is hidden from me and difficult to keep track of so I don't have true bearings on a complete path, sun rise is when I take the dog out for a walk by the lake. The lake itself gives a panoramic view and easy to tell where the sun is coming up over distinguishable landmarks like an island or a cell phone tower visible in the distance.

    For what it's worth, an astrolabe in the garden still shows noon at 12:00. At that point, degree of declination has no meaning - it would be the same at the Equator as it is at 45* North. It's the rising and setting that show how far the Earth is tilted towards the Sun in it's Northern hemisphere.

    On a similar note, I always used to stand out my front door in the evenings and see Orions Belt right in front of me. That familiar constellation is now almost straight up over the house, when it used to be right above the treeline it's now almost directly above.

    This is a case where I know what I've seen in the past, and know what I'm seeing now. And I can not explain the discrepency without involving tipping the Earth beyond normal limits and literally changing the North/South pole locations.
    Even in my madness I can't imagine this happening without someone else noticing.

    So why does the Sun now rise almost 30* North of where it has for the past two decades?

    Or am I completely wrong and nobody else can see this?
    CT Co-ordinator, Paintball Marshals

  2. #2
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    I can only assume Halb will know why things have changed.

  3. #3
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    im quite sure you're right. though i havent been alive long, i have noticed drastic changes in the seasons and weather. it's never consistant anymore. the timing of the earth has been thrown off.

  4. #4
    I'm pretty sure other people with PH.D's and Doctorates would have noticed this type of thing by now.

  5. #5
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    So the pyrate needs to lay off the RUM

  6. #6
    Have you done much research? Maybe this is somewhat common knowledge in the scientific community, and nothing really new, so its not in the publics eye.

  7. #7
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    The azimuthal location of the sunrise can vary quite a bit throughout the year, depending on where you live. You're at about 45 degrees north latitude. Believe it or not, at that latitude you can expect a 55 degree swing in sunrise location over the course of the year, from about 67 degrees east of north on the summer solstice to about 122 degrees east of north on the winter solstice.

    Here's a bit of an explanation:

    http://curious.astro.cornell.edu/que...php?number=186

    Here's a calculator where you can enter your latitude, longitude, and give it a date and a time of day, and it will calculate the azimuth and elevation of the sun at that point in time.

    http://www.srrb.noaa.gov/highlights/sunrise/azel.html


    Constellations appear to slowly move across the sky from night to night. This is because the earth is moving around the sun. At each sunset, the portion of the night sky that is directly overhead differs from the previous sunset by a little less than one degree. So while Orion was on the horizon at sunset during one part of the year, during other parts of the year it will appear directly overhead at sunset or may not be visible at all.

    For the past few years, near the summer solstice the sun has appeared to rise through a gap between two mountains in the distance, as viewed from my kitchen window. It's doing the same thing this year. I think you might be noticing things at different times throughout the year, and perhaps mixing them together in some way.

    BJJB

  8. #8
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    Quote Originally Posted by bjjb99
    Here's a calculator where you can enter your latitude, longitude, and give it a date and a time of day, and it will calculate the azimuth and elevation of the sun at that point in time.

    http://www.srrb.noaa.gov/highlights/sunrise/azel.html
    I'm going to give that a try.
    I'll go out on the beach and mark a compass in the sand and see if I'm actually imagining things. (things that have nothing to do with too much rum, I never hallucinate during a hangover) I could probably get a 30' circle which should get me to less than 2 degrees of error. Then compare that to NOAA.

    But I have asked neighbors "Where does the Sun come up?" and they invariably point to the island that has been my benchmark for a quarter-century.
    Yet the Sun still rises off my left shoulder when I face the island in the morning and it's only been during this calendar year that this has ever happened.

    Please don't think me ignorant of solar or celestial mechanics. I know what "ought" to be and my observations have previously been in accordance to the point that only the severity of deviation brought it to my attention at all. It's only recently that what I'm seeing is not what I would expect to see based on several decades of observation.

  9. #9
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    Simple test, if you can take a long exposure photograph at night...

    Put a camera on a tripod, aim it at Polaris, and take a long exposure photo. If Polaris traces a small diameter arc in the resultant image, then the Earth is just fine.

    BJJB

  10. #10
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    Quote Originally Posted by bjjb99
    Simple test, if you can take a long exposure photograph at night...

    Put a camera on a tripod, aim it at Polaris, and take a long exposure photo. If Polaris traces a small diameter arc in the resultant image, then the Earth is just fine.

    BJJB
    Polaris has not always been the "North" star. There's this little thing called "pressesion" which concerns the axial rotation of the poles.
    It's part of the reason the solar calendar (equinox to equinox) does not line up with the celestial calendar (fixed star to fixed star).
    That 6 hour difference each 12 months (approximately) is why we add one day every four years. But it's not quite 6 hours, Mathematically it works out that to account for those few minutes per year you skip any leap year that ends in double zero and is divisible by four. So the year 2000 was not supposed to be a leap year even though it was included in every calendar printed.

    I didn't invent this. The math was worked out by Pope Innocent the First back in the year 1154.

    Using Polaris as a fixed point doesn't really help in this situation unless I could compare the arc trace on a long term exposure to one taken previously under similar conditions.
    Since I'm not capable of doing that, I'm going to have to rely on attempting to trace the Sun path as far as I am able.
    We are less than one week from the furthest point (the Solar Equinox) and already the sunrise has retreated to the hills behind me, and sunset is in the hills behind me.
    This is just wrong. I should expect a little over 180* ~ not 250*...
    From what I'm seeing, my location is somewhere North of the polar circle but the maps say I'm not.

    (sigh) Dementia is often fun, but sometimes confusing. I blame it on the school system for making me learn spherical trig as a child.

  11. #11
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    Quote Originally Posted by Pyrate Jim
    Polaris has not always been the "North" star. There's this little thing called "pressesion" which concerns the axial rotation of the poles.
    Axial precession of the earth has a period of about 26,000 years. That's far too slow to account for what you've described -- namely, a significant shift in the observed sunrise/sunset points within the past year or so, after about 23 years of no observed changes.

    Precession of the ecliptic for the earth has a period of about 70,000 years. That's even slower and also cannot account for what you've described.


    Quote Originally Posted by Pyrite Jim
    It's part of the reason the solar calendar (equinox to equinox) does not line up with the celestial calendar (fixed star to fixed star).
    That 6 hour difference each 12 months (approximately) is why we add one day every four years. But it's not quite 6 hours, Mathematically it works out that to account for those few minutes per year you skip any leap year that ends in double zero and is divisible by four. So the year 2000 was not supposed to be a leap year even though it was included in every calendar printed.
    All the calendar adjustments you describe are not to compensate for precession. Rather they are the result of the earth's rotation and revolution not being a simple integer ratio of each other. There are 365.25 (and some change) rotations for every one revolution. The calendar corrections are put in place to maintain synchronicity between a calendar year and a seasonal year. The 26,000 year long cycle of where the north celestial pole is pointing has very little impact on this set of computations.


    Quote Originally Posted by Pyrite Jim
    Using Polaris as a fixed point doesn't really help in this situation unless I could compare the arc trace on a long term exposure to one taken previously under similar conditions.
    Just about any of the web-based astronomy sites can show you an image of the night sky, from your position on the earth, and often at any particular date and time you wish. You can use that to measure how far Polaris is supposed to be from the earth's north celestial pole. You can compare that with a single measurement made by you. No prior photo is required.


    Quote Originally Posted by Pyrite Jim
    Since I'm not capable of doing that, I'm going to have to rely on attempting to trace the Sun path as far as I am able.
    We are less than one week from the furthest point (the Solar Equinox) and already the sunrise has retreated to the hills behind me, and sunset is in the hills behind me.
    This is just wrong. I should expect a little over 180* ~ not 250*...
    I ran a quick computation for 45 degrees north latitude on the summer solstice (June 21). The sunrise should occur about 58 degrees east of north. Sunset should occur about 302 degrees east of north. That's slightly more than a 240 degree swing, and it's exactly what one should expect at that latitude this time of year.

    Check out the following URL:

    http://en.wikipedia.org/wiki/Solstice

    Look particularly at the diagrams labeled "Day arcs at XX* latitude". For the 50* latitude diagram, look at the summer solstice arc. Draw lines from the sunrise and sunset points to the observer, and eyeball-measure the external angle between them. You'll see that it's noticeably larger than 180 degrees -- it's closer to 270 degrees.

    Quote Originally Posted by Pyrite Jim
    From what I'm seeing, my location is somewhere North of the polar circle but the maps say I'm not.
    If you're seeing somewhere around 250 degrees between sunrise and sunset locations, then you're somewhere around a latitude of 45 degrees, which should be in agreement with where maps place you.

    I ran another calculation for someone sitting on the north polar circle for June 19, the date you made your most recent post. On that day, someone sitting on the north polar circle would have measured almost 290 degrees between rise and set points. That's significantly greater than what you've measured, so you must be south of that latitude.


    Hope this helps,

    BJJB

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