1553
Sea Level (europe.pub)
submitted 9 months ago by to c/science_memes@mander.xyz
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Alt text: They're up there with coral islands, lightning, and caterpillars turning into butterflies.

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[–] 40 points 9 months ago (7 children)

It makes 12 months because the lap the Earth makes is deducted from the 13 the moon makes, so effectively it makes 12 cycles around the Earth.

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  • [–] 5 points 9 months ago* (last edited 9 months ago) (6 children)

    You don't know what you're talking about

    13x28=364. The moon makes 14 sidereal orbits, not 13. The reason the year is split into 12 months is a combination of Roman dipshittery and the fact that 12 is divisible by 2, 3, 4, and 6. The number of factors of 12 made 12 and 60 way easier to work with for societies that hadn't invented the decimal point yet.

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  • [–] 6 points 9 months ago (2 children)

    Then please explain how the Hebrew calendar, and all other lunisolar calendars (calendars which follow both the solar year and the lunar cycle) have 12 months most years? https://en.wikipedia.org/wiki/Lunisolar_calendar

    "The majority of years have twelve months but every second or third year is an embolismic year, which adds a thirteenth intercalary, embolismic, or leap month."

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  • [–] 2 points 9 months ago (1 child)

    Not who you asked, but after looking into it it's because the moon takes about 29.5 days to complete a full cycle of phases (one synodic month), giving it time to do so roughly 12 times per year.

    I can't quite wrap my head around it, but I think the explanation for why sidereal and synodic months differ lines up with your initial explanation. Because we're also moving, the moon has to move further to achieve the visual change of moon phases.

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  • [–] 1 point 9 months ago (2 children)

    Can you provide a source for 14 orbits? Everything in my search results says 13 and some change.

    Wikipedia says one sidereal month is 27.321661 days and a sidereal year is 365.256 days.

    365.256/27.321661 ≈ 13.37

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  • [–] 1 point 9 months ago (1 child)

    a sidereal year is 365.256 days.

    No. A sidereal year is 366.24 days.

    And 11 days isn't "and some change"

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  • [–] 2 points 9 months ago

    The figures in my post are ephemeris days since that's the way Wikipedia lists them.

    https://en.wikipedia.org/wiki/Sidereal_year

    https://en.wikipedia.org/wiki/Lunar_month#Sidereal_month

    "And some change" is a phrase to refer to a number following a decimal point, meaning the sources I find claim there are thirteen point something sidereal months per year, at a figure too low to round to 14. Here are some example sources:

    https://en.wikipedia.org/wiki/Orbit_of_the_Moon#Lunar_periods

    http://scienceline.ucsb.edu/getkey.php?key=1126

    I still can't find a source which says the moon makes 14 sidereal orbits per year, using any definition of year.

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