Lesson Notes By Weeks and Term v4 - SHS 3
BASIC PHYSICS
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BASIC PHYSICS
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Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 7
Grade code: 3.1.1.LI.2
Strand code: 1
Sub-strand code: 1
Content standard code: 3.1.1.CS.3
Indicator code: 3.1.1.LI.2
Theme: MECHANICS AND MATTER
Subtheme: BASIC PHYSICS
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Welcome, future scientists and engineers! Today, we are looking at something very special. We often think of Physics, especially astronomy, as something that happens in big labs in America or Europe with powerful telescopes. But what if I told you that our own great-grandparents, living right here in Ghana, were expert astronomers? They used the Sun, the Moon, and the stars as their clock, their calendar, their compass, and their guide for farming and fishing. This lesson will connect the Physics in our textbooks to the wisdom in our culture.
This section contains the core knowledge for the lesson. Read it carefully. Part A: Defining Our Terms
Before we connect to our culture, let's be clear on the scientific terms. Astronomy: This is the scientific study of everything outside of Earth's atmosphere. It focuses on celestial objects like the Sun, the Moon, planets, stars, and galaxies. Astronomers observe these objects, their positions, their movements, and their physical properties. *Simple Analogy:* Think of astronomy as creating a detailed map of a huge city (the universe). It tells you where the buildings (stars), streets (orbits), and neighbourhoods (galaxies) are. Cosmology: This is a branch of astronomy that studies the universe as a whole. It asks the "big questions": How did the universe begin? How has it changed over time? What is its ultimate fate? It deals with theories about the origin and evolution of the entire cosmos. *Simple Analogy:* If astronomy maps the city, cosmology asks: "Who built this city? Why was it built this way? What will it look like in 1000 years?"
The key difference is scope: Astronomy studies the *parts* of the universe, while Cosmology studies the *whole* universe and its history. Part B: Indigenous Ghanaian Astronomy in Practice
Our ancestors were keen observers. Their survival depended on understanding the patterns in the sky. This knowledge, passed down through generations, is a form of science. Agriculture and the Celestial Calendar The Challenge: How did a farmer in Northern Ghana, centuries ago, know the best time to plant millet or guinea corn? There was no meteorological service to announce the start of the rainy season. The Indigenous Solution: They observed the stars. The appearance of specific star clusters at a certain position in the sky at dusk or dawn signalled the change in seasons. Specific Example (Akan & others): The Pleiades star cluster, a small, dipper-like group of stars, is very important. In Twi, it is called *Asonomma* ("the seven children"). Its appearance in the pre-dawn sky signalled the start of the planting season. Its disappearance from the evening sky signalled the time for harvesting. The Physics Behind It: This works because the stars we see in the night sky change throughout the year. This is due to the Earth's revolution (orbit) around the Sun. As the Earth moves to a different position in its orbit, our "window" to the universe changes, making different constellations visible. The appearance of the Pleiades is a reliable indicator of a specific time of year, which correlates with the onset of the rains. Fishing and the Lunar Tides The Challenge: How does a fisherman in Elmina or Axim know when the tide will be high (making it difficult to launch a canoe) or low (exposing rocks or good spots for catching certain fish)? The Indigenous Solution: They observed the phases of the Moon. Experienced fishermen have a deep, practical understanding of the relationship between the Moon and the ocean tides. Specific Example (Fante/Ga): Fishermen know that spring tides (very high high-tides and very low low-tides) occur during the New Moon and the Full Moon. Neap tides (less extreme tides) occur during the first and third quarter moons. This knowledge dictates their daily fishing schedule and ensures their safety. The Physics Behind It: Tides are caused by the gravitational pull of the Moon (and to a lesser extent, the Sun) on Earth's oceans. During a Full Moon and New Moon, the Sun, Earth, and Moon are aligned (in a straight line, called a syzygy). Their gravitational forces combine, pulling the water more strongly and creating the extreme spring tides. During the quarter moons, the Sun and Moon are at a 90° angle to each other relative to Earth. Their gravitational pulls partially cancel each other out, leading to weaker neap tides. This is a direct application of Newton's Law of Universal Gravitation! Festivals, Culture, and Timekeeping The Challenge: How were major community events and festivals synchronized across different towns and villages without a modern calendar? The Indigenous Solution: A lunar or lunisolar calendar was used. Many Ghanaian festivals are timed to begin on a specific phase of the moon in a specific season. Specific Example (Ga): The Homowo festival is a major event for the Ga people, celebrating the end of a famine and the harvest. The timing is determined by a complex lunar calendar observed by the traditional priests (Wulɔmei). The start of the festival season is marked by the planting of maize (*Nmaadumo*), and the date of the festival itself is calculated based on the lunar cycles that follow. Specific Example (Akan): The Akan calendar system includes a 40-day cycle called *Adaduanan*. This is based on the combination of a 6-day week and a 7-day week, and certain days within this cycle are considered sacred or auspicious, guided by celestial observations. Part C: Indigenous Cosmology vs. Scientific Cosmology