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How to calculate the phase of the moon very, very badly!!

How to calculate the phase of the moon very, very badly!!

This talk is about how, despite “common knowledge”, lunar cycles are not 28 days long, and in fact lunar cycles don’t have a single numerical length! You’ll hear about several very bad ways to calculate the phases of the moon, why they seemed reasonable at the time, and exactly how it took three years from the time one app shipped to the App Store before the calendar was even arguably correct.

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André Arko

February 24, 2019
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Transcript

  1. Everyone Knows a Lunar Cycle is 28 Days or, falsehoods

    werewolves believe about time
  2. None
  3. None
  4. None
  5. None
  6. None
  7. None
  8. None
  9. 27.321661 days a sidereal month

  10. ...two years later...

  11. M T W Th F S Su   

                           
  12. M T W Th F S Su   

                           
  13. M T W Th F S Su   

                           
  14. M T W Th F S Su   

                           
  15. ⁉ ⁉ ⁉ ⁉

  16. sidereal schmidereal

  17. lunar phases are synodic months

  18. synodic months are 29.530587981 days

  19. averages are lie-candy for your brain

  20. thanks BDAstroCalc!

  21. 0 0.5 0.9

  22.          

                    
  23.          

                    
  24.          

                     0.5235? 0.6852? 0.9855?
  25.         0.614 0.638

    0.652 Feb 2 Feb 3 Feb 4 When is the half-moon?
  26. midnight 02/23 midnight 02/24 midnight 0.46 0.49 0.52  

  27. Victory!!!

  28. witchy.co witchy.co/trig andre.arko.net twitter.com/sailorhg twitter.com/indirect