This has become a little bit of an obsession with me. I think inclusive science is great. But it has to be _correct_ and I worry that the way it is being presented on the internet glosses over the details to the point it becomes a just-so story, rather than something that was the product of careful observation and searching for patterns – i.e. science. I would love for someone to instruct me, that is why I am posting it.
In MN – a 6th grade standard reads “6E.220.127.116.11 Communicate how a series of models, including those used by Minnesota American Indian Tribes and communities and other cultures, are used to explain how motion in the Earth-Sun-Moon system causes the cyclic patterns of lunar phases, eclipses and seasons. (P: 8, CC: 1, CI: ESS1) Examples of cultures may include those within the local context of the learning community and within the context of Minnesota. Emphasis is on students questioning the limitations of their models and revising them to account for new observations. Models may be physical, graphical or conceptual.”
If you read a website like https://pimaki.ca/the-lunar-calendar-explained/ you will see: "Why is the lunar calendar on the turtle’s shell? The turtle shell is a visual match for the days and moons in a lunar year. If you look at a turtle’s shell, you will see an outer ring of small scales. These represent the 28 days in a lunar month. You will also see larger scales inside the centre of the shell. These large scales represent the 13 moons that occur each lunar year ... The lunar calendar has 364 days. The solar calendar has 365 days."
The Lunar Calendar, Explained - Pimachiowin Aki
The moon serves many purposes — lighting the land throughout night and stabilizing the climate — but did you know Anishinaabeg in Pimachiowin Aki track its movement to know when to plant wild rice? Mapped out on a turtle shell, the lunar calendar guides us throughout the year. Bloodvein First Nation Guardian Melba Green shares how. See the calendar.
pimaki.ca But this is doesn’t ACTUALLY work. Think about it - 52 weeks x 7 days a week = 364. How far does your birthday move from year to year (not counting a leap year?) - it moves 1 day back. If last year it was a Tuesday, this year it is a Monday because 365 (solar year) and 364 (52x7) are off by 1day. If 28x13 (= 364) was correct, the first moon of the year would only move by 1 day each year as well. But if you look at the actual dates of the full moons that you can observe (in the attachment – I can’t paste a picture on this website apparently), you will see that they are more than 28 days apart, they are 29.5 days apart (so this doesn’t line up with 28 day lunar months) AND that they move by about 2 weeks (not 1 day) from year to year. If you use 28 days to count your lunar months, your second month starts while the first moon is still waning crescent, and by the end of about a year, you are off by 2 weeks, with a new moon where a full moon should be.
(The problem with 2 lengths to a lunar month is that the moon goes around the earth in ~28 days. But during these 28 days, the earth has made 1/13 of a circle around the sun. So the angles the sun, earth and moon no longer give it a full moon observed from earth … it has to go another 1.5 days to get to the position where it again makes the correct angle with the sun and earth to appear full again. If you are a space alien observing from above the solar system, or make a lot of fancy orbit diagrams, this is more obvious. But if you are STRICTLY observing moons on earth, then this 28 day lunar month doesn’t actually work.
I am not saying that the Native Americans did not use the sun, moon and stars to plan the year. [the standard] - The Mayans, in particular, could predict an eclipse way out there with great accuracy. They found the pattern.
I am not saying that they did not count time with the turtle shell - 28x7 does count pretty close to a solar year.
I am not saying that they did not name moons, have 13 of them, etc.
I am saying, though, that in the simplified form being presented on the internet, this does not work. Lunar months OBSERVED FROM EARTH are longer - 29.5 days, not 28. Because of this, you can't make a 1:1 correspondence between the turtle shell, 28 day lunar months, the observed moons, and the solar year.
Perhaps Jim Rock (Native American astronomer associated with the University of Minnesota and a keynote speaker at 2022 MnSTA/MnCOSE conference) said the key thing - that so much knowledge was lost by the genocide and forcing young people into Indian schools so they could not learn this from their ancestors. We are t