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B History of RA [why is the vernal equinox used?]

  1. Dec 15, 2017 #1

    nearc

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    i failed to find the history of RA [right ascension] and why the vernal equinox was picked as the starting point on the web or in the forums here. does anyone know the origins of RA? picking a solstice or equinox is obvious but why the vernal? maybe because spring in the northern hemisphere inspires hope? if anyone has a real answer i would be most appreciative.

    on a side note, i did potentially come across its start date http://www.dictionary.com/browse/right-ascension
     
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  3. Dec 15, 2017 #2

    Orodruin

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    To be honest I am not sure, but which one would you choose? Clearly, as you say, there are four more or less canonical possibilities and you need to select one of them. Had it been any other, you might be here asking the very same question about that one. I suspect you may be looking for an answer where none is to be found other than it just happened to be chosen among the four.
     
  4. Dec 22, 2017 #3

    sophiecentaur

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    Many years ago, long before I knew anything at all about Astronomy, I did a Marine Navigation course which included some Astro Nav. The First Point of Aries (aka Vernal Equinox) was the origin used for all the calculations. Greenwich Hour Angle was used instead of RA, if I remember right. I guess that that would be a good choice because navigators in both hemispheres would be in a good position to see more common stars during an equinox. That would be good for calibration, (I think?).
     
  5. Dec 22, 2017 #4

    jim mcnamara

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    Okay. History. The new year on the Roman calendar started on March 15 - the Ides of March. The Sun was just coming into Aries. @sophiecentaur explaining navigation actually gave the answer. Aries is the starting point for the zodiac. Instead of me blabbing:

    http://www.schooloftheseasons.com/spring.html
    The more modern Julian calendar (the forerunner of our Gregorian calendar) was later changed primarily by Dionysius exiguus, and the New year moved in 525 AD to January 1. Dionysius actually changed the year numbers, and estimated the birth of Christ and the start of the calendar. 500+ years late. The first year in the new improved calendar was 525 AD. He "invented" Anno Domini.

    Short answer: it is all made up stuff, except for the actual equinoxes/solstices.
     
  6. Dec 25, 2017 #5

    stefan r

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    I do not have any facts on this. However, most people who lived on earth were farmers by profession. Most seeds sprout in the spring and are harvested in the fall. Spring being the starting point is the natural perspective.

    Edit:
    Hunter/gatherers go back much further than farmers. They would also have a perspective linked to plant life cycles.
    Stonehenge predates writing. Not likely to find out what they were thinking in detail.
    The Egyptians measured off of Sirius.
     
    Last edited: Dec 25, 2017
  7. Jan 6, 2018 #6

    sophiecentaur

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    I think that is quite an insightful. It implies that ancient hominids were relieved that winter had actually passed and that they could rely on the annual cycle starting again - the most optimistic part of the year; even moreso than the winter solstice.
     
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