12 December Science 8 Modelling the Sun-Earth-Moon System: Phases and their connection with times of day to see the moon

  • Mindful moment
  • Review last classes (think about model and modeling–kinds of model, benefits, pitfalls–thinking patterns related to models–analogies, metaphors, theories–how do these work in our minds?)
  • Preview today’s blog
  • Set up today’s DSN.  Copy and paste link to today’s blogpost. Write an anticipatory statement for each of the 7 DSN entry items. Complete those items as the class progresses / after this class and before the next.
  • Questions
  • * * * *


  • Have your observations of the moon ready.
  • Have your answers to questions about the moon from the last class ready.
  • Making a “working” model of the Sun-Earth-Moon System
  • What is modeled? What is not modeled?
  • What is the real object, system, pattern? How is it represented? (Representation –> Target)
  • What is the structure of a model? What do you think of this: <https://serc.carleton.edu/introgeo/models/Def.html>?
  • An article by Dr. F: rethinkingmodels
  • Building the model
  • Operating the model

Some questions about the model:

  • How are day and night modeled?
  • How are the phases of the moon modeled?
  • How is the orbit of the moon modeled?
  • How is the orbit of the moon “synchronized” with the rotation of the earth (day and night) about its axis?
  • How can a lunar eclipse be modeled?
  • How can a solar eclipse be modeled?
  • Why do eclipses NOT occur for every lunar cycle?
  • How do we know which way the moon orbits–by observation from our earthbound point of view?
  • Why is it important to “point to the sun and moon simultaneously” to understand the relation between the phases, the relative positions of the sun, earth, moon, and the times of day the moon is seen?
  • Where does our model not correspond to reality?
  • Can you arrange the earth sun and moon to correspond to a particular observation you made on a certain date and time in a certain place? Try it.
  • Why do you think so many people have misunderstandings or no understandings of the moon and its phases and times of appearance? What are the barriers to understanding?
  • What are some assumptions behind the model? Light travels in a straight line; the moon’s light is light reflected from the sun; other?
  • What are your questions?

Useful pictures: http://www.stargazing.net/david/moon/index29days.html

Check out this video of an Orrery owned by Jules Verne <https://www.youtube.com/watch?v=nlgyXY3vPd4>

Check out the Majestic Clockwork: https://www.dailymotion.com/video/x1zzkos

Other episodes from The Ascent of Man are excellent and fascinating–Stories of how we know.

Newton, the Apple, and the Moon: https://www.independent.co.uk/news/science/the-core-of-truth-behind-sir-isaac-newtons-apple-1870915.html

Predicting eclipses <https://www.atlasobscura.com/articles/how-to-predict-eclipse-computer-math-antikythera>

Astronomical Seasons (from Wikipedia <https://en.wikipedia.org/wiki/Season>)

UT date and time of
equinoxes and solstices on Earth[14]
event equinox solstice equinox solstice
month March June September December
day time day time day time day time
2013 20 11:02 21 05:04 22 20:44 21 17:11
2014 20 16:57 21 10:51 23 02:29 21 23:03
2015 20 22:45 21 16:38 23 08:21 22 04:48
2016 20 04:30 20 22:34 22 14:21 21 10:44
2017 20 10:28 21 04:24 22 20:02 21 16:28
2018 20 16:15 21 10:07 23 01:54 21 22:23
2019 20 21:58 21 15:54 23 07:50 22 04:19
2020 20 03:50 20 21:44 22 13:31 21 10:02
2021 20 09:37 21 03:32 22 19:21 21 15:59
2022 20 15:33 21 09:14 23 01:04 21 21:48
2023 20 21:24 21 14:58 23 06:50 22 03:27

Astronomical timing as the basis for designating the temperate seasons dates back at least to the Julian calendar used by the ancient Romans. It continues to be used on many modern Gregorian calendars worldwide, although some countries like Australia, New Zealand, and Russia prefer to use meteorological reckoning. The precise timing of the seasons is determined by the exact times of transit of the sun over the tropics of Cancer and Capricorn for the solstices and the times of the sun’s transit over the equator for the equinoxes, or a traditional date close to these times.[15]

The following diagram shows the relation between the line of solstice and the line of apsidesof Earth’s elliptical orbit. The orbital ellipse (with eccentricity exaggerated for effect) goes through each of the six Earth images, which are sequentially the perihelion (periapsis—nearest point to the sun) on anywhere from 2 January to 5 January, the point of March equinox on 19, 20 or 21 March, the point of June solstice on 20 or 21 June, the aphelion(apoapsis—farthest point from the sun) on anywhere from 4 July to 7 July, the September equinox on 22 or 23 September, and the December solstice on 21 or 22 December.

Illustration of seasonal distances from Earth to the Sun

Note: Distances are exaggerated and not to scale

These “astronomical” seasons are not of equal length, because of the elliptical nature of the orbit of the Earth, as discovered by Johannes Kepler. From the March equinox it currently takes 92.75 days until the June solstice, then 93.65 days until the September equinox, 89.85 days until the December solstice and finally 88.99 days until the March equinox.

About rfrazier

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