4 Matching Annotations
  1. Mar 2022
    1. The ecliptic is tilted towards the north in the southern hemisphere,and towards the south in the northern hemisphere. Many people inthe southern hemisphere prefer housing with north-facing windowsand balconies and that take advantage of the light and warmth of theSun. Venture north of the equator, and that preference is for south-facing properties. First Peoples of the world follow the samepreference, with homes, villages and cities constructed to takeadvantage of the Sun.

      Many cultures in the world face their windows, balconies, and other architecture to take advantage of the sun (for light and warmth). Because the ecliptic is tilted towards the north in the southern hemisphere and towards the south in the northern hemisphere, people in the north of the equator prefer south-facing properties and people south of the equator prefer north-facing properties.

    2. The path of the Sun is called the ecliptic in Western astronomysince it is along this path that eclipses occur.

      What is the path of the sun called? :: the ecliptic

      Eclipses occur on the path of which heavenly body? :: the sun

  2. Feb 2022
    1. https://www.scientificamerican.com/article/an-ancient-greek-astronomical-calculation-machine-reveals-new-secrets/

      Overview and history of the Antikythera mechanism and the current state of research surrounding it.

      Antikythera mechanism found in diving expedition in 1900 by Elias Stadiatis. It was later dated between 60 and 70 BCE, but evidence suggests it may have been made around 205 BCE.


      One of the primary purposes of the device was to predict the positions of the planets along the ecliptic, the plane of the solar system.

      The device was also used to track the positions of the sun and moon. This included the moon's phase, position and age (the number of days from a new moon). It also included the predictions of eclipses.

      Used to track the motions of the 5 known planets including 289 synodic cycles in 462 years for Venus and 427 synodic cycles in 442 years for Saturn.

      Risings and settings of stars indexed to a zodiac dial


      metonic cycle, a 19-year period over which 235 moon phases recur; named after Greek astronomer Meton, but discovered much earlier by the Babylonians. The Greeks refined it to a 76 year period.

      saros cycle, the 223 month lunar cycle which was used by the Babylonians to predict eclipses. A dial on the Antikythera mechanism was used to predict the dates of the solar and lunar eclipses using this cycle.

      synodic events: conjunctions with the sun and its stationary points


      Archimedes - potentially the designer of an early version of the Antikythera mechanism

      Elias Stadiatis - diver who discovered the Antikythera mechanism

      Albert Rehm - German philologist who the numbers 19, 76 and 223 inscribed on fragments of the device in the early 1900s

      Derek J. de Solla Price, published Gears from the Greeks in 1974. Identified the gear train and developed a complete model of the gearing.

      Michael Wright - 3D x-ray study in 1990 using linear tomography; identified tooth counts of the gears and understood the upper dial on the back of the device

      Tony Freeth - author of article and researcher whose made recent discoveries.

    2. We added a mechanism for the variable motion of the sun and an epicyclic mechanism for calculating the “nodes” of the moon—the points at which the moon’s orbit cuts through the plane of the ecliptic, making an eclipse possible. Eclipses happen only when the sun is close to one of these nodes during a full or new moon. Medieval and renaissance astronomers called a double-ended pointer for the nodes of the moon a “dragon hand.” The epicyclic gearing for this dragon hand also exactly explained a prominent bearing on one of the spokes that had previously appeared to have no function.

      The nodes of the moon are the points at which the moon's orbit cuts through the plane of the ecliptic. These nodes make an eclipse possible and they happen only when the sun is close to one of these nodes during either a full or a new moon.

      Medieval and renaissance astronomers called a double-ended pointer for the nodes of the moon a "dragon hand".