ADM-Physical-Science-Q2-Module-1

Models of the Universe

Historical Overview

• The model of the solar system has roots in ancient Greek astronomy, influencing our current understanding of celestial bodies, including the sun, moon, stars, eclipses, and constellations.

• Earlier studies in Elementary Science introduced the elements of the solar system, while this module dives deeper into ancient Greek perspectives and how the solar system model evolved.

• This activity aims to familiarize students with the coordinate system of the celestial sphere, drawing parallels to Earth's geographical coordinates:

  1. North Pole: Corresponds to Earth's North Pole.

  2. South Pole: Corresponds to Earth's South Pole.

  3. Latitude: Equivalent to Earth's latitude, indicating north-south position.

  4. Longitude: Represents Earth's longitude, indicating east-west position.

  5. Ecliptic Path: The apparent path the sun takes across the celestial sphere.

  6. Intersection Point: Where the ecliptic intersects the celestial equator.

Understanding Earth's Shape

Greek Observations

• The Greeks established the Earth as spherical long before Plato, primarily through observations:

  • The circular shadow during lunar eclipses, indicating a spherical object (Earth) casting the shadow.

  • Differences in star visibility based on traveling north or south.

  • Eratosthenes' Measurement: Noted no shadow in Syene (summer solstice) versus a 7.2° shadow in Alexandria, asserting that the Earth’s curvature caused this difference. The distance between the two cities (5000 stadia) led him to calculate Earth’s circumference as approximately 40,000 kilometers.

Significance of a Spherical Earth

• The Greeks believed in a symmetrical universe with Earth at the center, reinforcing the notion of a spherical Earth.

Early Astronomy: Pre-Telescope Knowledge

• Civilizations like the Babylonians, Assyrians, Egyptians, Chinese, and Mayans recorded astronomical events without telescopes:

  • Egyptians tracked the annual cycle of the Nile via Sirius and developed a 365-day calendar.

  • Chinese civilizations observed comets and other celestial phenomena, while the Mayans created calendars based on Venus.

  • Polynesians used stars for navigation, showcasing their reliance on observational astronomy.

Diurnal and Annual Motion

Diurnal Motion

• Defined as the apparent daily movement of celestial bodies due to Earth's rotation, exemplified by the sun rising in the east and setting in the west.

• Greek astronomers classified stars based on their movements:

  • Fixed Stars: Maintain the same positional arrangement.

  • Planetes: Translating to