Astronomical-Phenomena Physical Science 12 .pptx

Physical Science 12

1. Examples of Astronomical Phenomena Before the Advent of Telescope

2. 1. Rising and Setting of the Sun Figure 1: The figure shows the ancient stele used as a gnomon, a primitive version of sundial

3. 🌞 Ancient Sundials (Gnomon) Babylonian and Egyptian civilizations used a primitive sundial called a gnomon to track the Sun’s motion. By observing the shadows, they recorded: The Sun rises in the east, reaches its highest point at midday, and sets in the west. The rising and setting points of the Sun on the horizon change throughout the year in a predictable pattern. These variations are linked to seasonal changes in climate.

4. ✨ Sun and the Celestial Sphere The Sun’s brightness hides the stars during the day, though the Moon is often visible. The Sun appears to move along a circular path on the celestial sphere over a year. 🌍 Earth’s Orbit and Tilt Earth’s elliptical orbit causes the Sun to move at slightly different speeds across the sky. Earth is tilted at 23.4°, which creates seasonal changes: Summer Solstice (~June 21) – Longest day of the year when the North Pole tilts toward the Sun. Winter Solstice (~December 21) – Shortest day of the year when the North Pole tilts away.

5. 📅 The Ecliptic and Time Variations The ecliptic is an imaginary line or path in the sky that marks the annual journey of the Sun, Moon, and planets against the background of stars. Due to Earth’s rotation and orbit, the Sun rises about 4 minutes later each day with respect to the stars. Day length changes throughout the year, repeating the cycle annually.

6. PHASES OF THE MOON Figure 2: The figure shows the eight (8) phases of the moon

7. 🌍 The Moon and Its Orbit A moon (satellite) is a small celestial body orbiting a planet. Earth’s Moon is the fifth largest in the solar system. Distance from Earth: ~384,000 km. The Moon is 4 times smaller than Earth's width. Due to Earth’s gravity, only one side of the Moon is visible from Earth.

8. 🌗 How the Moon’s Phases Occur The Moon orbits Earth while rotating on its axis, causing changing phases. Half of the Moon is always illuminated by the Sun, but we see different portions of it. The Moon takes:27.3 days to orbit Earth (Sidereal Month).29.5 days to complete a full cycle of phases (Synodic Month).

9. 🌖 The Lunar Cycle (8 Phases) 🌑 New Moon – Moon is between Earth and Sun, fully dark. 🌒 Waxing Crescent – A small lit portion appears. 🌓 First Quarter – Half of the Moon is illuminated. 🌔 Waxing Gibbous – Almost full but not yet. 🌕 Full Moon – Entire face of the Moon is lit. 🌖 Waning Gibbous – Starts decreasing in light. 🌗 Last Quarter – Half-lit again, but opposite side. 🌘 Waning Crescent – Only a thin crescent remains before returning to a New Moon.

10. ECLIPSES

11. 🌕 Lunar Eclipse Occurs when Earth is between the Sun and Moon, casting a shadow on the Moon. Always happens during a Full Moon. Usually occurs two weeks before or after a solar eclipse. Types of Lunar Eclipse: Total – Entire Moon passes through Earth's shadow, appearing reddish. Partial – Only part of the Moon is in shadow. Visible to everyone on Earth's night side.

12. ☀️ Solar Eclipse Happens when the Moon comes between Earth and the Sun, blocking sunlight. Always occurs during a New Moon. Ancient civilizations feared eclipses, believing they signaled disasters. Types of Solar Eclipse: Total Eclipse – The Sun is completely covered by the Moon, causing total darkness (totality). Partial Eclipse – Only part of the Sun is covered. Annular Eclipse – The Moon is too far to fully cover the Sun, leaving a bright ring (annulus). Totality Duration - Averages 2–3 minutes, max 7.5 minutes.

13. DIURNAL MOTION Definition - The apparent daily motion of celestial bodies due to Earth’s rotation. Diurnal Circle: The circular path taken by stars, the Sun, and planets. Direction of Motion: East to West across the sky. Counter-clockwise around Polaris (North Star). Sun’s Apparent Motion: Rises in the East, sets in the West due to Earth's rotation.

14. ANNUAL MOTION Definition - The apparent yearly movement of stars due to Earth’s revolution around the Sun. Ecliptic - The Sun’s 360° annual path on the celestial sphere. Seasonal Changes - Altitude of the Sun varies – highest at summer solstice, lowest at winter solstice. Sunrise/Sunset shifts – North of East in summer, South of East in winter. Zodiac Constellations - As the Sun moves along the ecliptic, different constellations become visible throughout the year.

15. Precession of the Equinoxes Equinoxes - Points where the ecliptic (Sun’s path) intersects the celestial equator. 🌸 Vernal Equinox: March 20 🍂 Autumnal Equinox: September 22 Equal day & night during equinoxes. Precession - A slow "wobbling" motion of Earth's rotational axis due to the gravitational pull of the Sun & Moon. Cycle Duration - 26,000 years. Effect- The North Pole’s reference star will change over time. 🌟 Currently: Polaris → Future: Vega.

16. Planets Discovered Before the Invention of Telescope

17. THEORETICAL FRAMEWORK AND MODELS Geocentric Model – The ancient Greeks, such as Aristotle and Ptolemy, developed a geocentric model, placing the Earth at the center of the universe Epicycles – To explain the complex motions of planets, astronomers developed the concept of epicycles, where planets moved in smaller circles within their larger orbits. Spherical Trigonometry – Ancient mathematicians and astronomers used spherical trigonometry to calculate the positions and distances of celestial bodies.

18. ACTIVITY 1. Group Work: Divide students into small groups and provide each group with an image of an astronomical phenomenon (e.g., eclipse, comet, supernova). 2. Task: • Identify the phenomenon. • Research how early astronomers (Babylonians, Greeks, Chinese, Mayans) interpreted it. • Compare their interpretation with modern scientific explanations. 3. Presentation: Each group will present their findings briefly (2 minutes per group).

19. Performance Task “Sky Observers Then and Now” 1. Students will create a mini poster or infographic comparing an ancient interpretation of an astronomical event with modern scientific understanding. 2. They will write a brief explanation of how knowledge about that phenomenon has evolved.