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--- courses:ast100:7.3 [2026/03/23 10:21] – [3. Planets and the zodiac] asad
+++ courses:ast100:7.3 [2026/03/23 10:32] (current) – [2. Moon and eclipses] asad
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 The ancient Babylonians significantly advanced these early timekeeping methods by blending astronomy with complex mathematics. Observing that the Sun returned to its original stellar position after 365 days, they smartly established a formalized circular calendar model. Because they actively utilized a base sixty mathematical framework, dividing a complete celestial circle into exactly 360 separate degrees felt logical and natural. Consequently, they firmly declared that the Sun traveled exactly one degree each day. This brilliant Babylonian innovation synchronized solar movement with geometry, permanently establishing the mathematical foundation for modern human calendars today.
-===== - Moon and eclipses =====
+===== - Moon, month and eclipses =====
 {{https://upload.wikimedia.org/wikipedia/commons/6/6a/Moon_Phase_Diagram_for_Simple_English_Wikipedia.GIF?nolink&600}}
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 The seven-day week is a celestial legacy where each day was originally dedicated to one of the seven classical "planets" visible to ancient astronomers: the Sun, the Moon, Mars, Mercury, Jupiter, Venus, and Saturn.
-^ English ^ Bangla ^ German ^ Italian ^ Persian [Planetary] ^
+^ English ^ Bangla ^ German ^ Italian ^ Persian ^
 | Sunday [Sun's Day] | Robibar [Day of the Sun] | Sonntag [Sun day] | Domenica [Lord's Day] | Khorshid [Day of Sun] |
 | Monday [Moon's Day] | Shombar [Day of the Moon] | Montag [Moon day] | Lunedì [Moon day] | Mah [Day of Moon] |
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 ===== - Stars and the constellations =====
+{{https://upload.wikimedia.org/wikipedia/commons/8/89/Constellations%2C_equirectangular_plot%2C_Menzel_families.svg?nolink}}
+The figure represents the celestial sphere (sky as viewed from earth in all directions) flattened into a two-dimensional map, utilizing a projection method similar to how Google Earth or traditional cartography flattens the spherical globe of the Earth. In this astronomical projection, the horizontal x-axis represents Right Ascension, which is the celestial equivalent of longitude, measured in hours, minutes, and seconds eastward from the March equinox. The vertical y-axis represents Declination, corresponding directly to terrestrial latitude, measured in degrees north or south of the celestial equator. This grid allows astronomers to precisely locate any celestial object within the vast, seemingly infinite expanse of the night sky by using these fixed and standardized coordinates.
+Just as the terrestrial globe is divided into distinct countries with defined borders, the celestial map is partitioned into 88 official constellations as recognized by the International Astronomical Union (**IAU**). The various colors in the diagram represent the historical eras during which these boundaries and groupings were formalized or introduced into modern stellar cartography. According to the legend, the different hues correspond to significant years of development, specifically 1592, 1603, 1613, 1692, and 1763. These dates mark the specific contributions of various astronomers and explorers who filled the gaps in the southern sky or refined classical Greek groupings to create a comprehensive, global celestial standard.
+The constellations are often organized into families based on their shared history, position, or mythological themes, providing both astronomical and cultural significance to the viewer. For instance, the Zodiac family lies along the ecliptic, while the Perseus family contains characters from the Andromeda myth, including Cepheus and Cassiopeia. Astronomically, these groupings help observers navigate the sky and identify seasonal patterns, acting as a celestial filing system. Culturally, they serve as a preservation of ancient oral traditions and scientific observations. By grouping stars into recognizable figures, ancient and modern civilizations alike created a mnemonic device to track time, navigate the seas, and explain the cosmos.
+The prominent dotted line bisecting the map is the ecliptic, representing the apparent path the Sun follows across the celestial sphere over the course of a year. This path also marks the plane of the Earth's orbit and is the region where planets and the Moon are consistently observed by astronomers. The names of the constellations found here and throughout the map offer a profound window into the mythological history of humanity, reflecting the deities and heroes of diverse cultures. From ancient Greek myths to the scientific instruments of the Enlightenment, the sky remains a narrative record of human imagination and our enduring quest to understand the universe.