Education Always

Level: JHS, Basic 9  |  Subject: Integrated Science  |  Strand: Systems  |  Topic: The Solar System: Eclipses, Tides and Satellites

Curriculum reference: B9.3.2.1 Understand eclipses, tides, and satellite technology. Indicator B9.3.2.1.1: Explain the occurrence of solar and lunar eclipses. All the exemplars are merged into one set of notes.

1. Sun, Earth and Moon

The Earth goes round the Sun in one year. The Moon goes round the Earth in about 27 days (a month). The Moon does not make its own light. It shines by reflecting sunlight. The changing shape of the lit part we see is called the phases of the Moon.

2. Shadows: Umbra and Penumbra

• Umbra: the darkest part of a shadow where all the light is blocked.
• Penumbra: the lighter part of the shadow where only some light is blocked.

3. Solar Eclipse

A solar eclipse happens when the Moon passes between the Sun and the Earth and blocks sunlight from reaching part of the Earth.

• Order: Sun, Moon, Earth.
• It happens at new moon.
• People in the umbra see a total solar eclipse (day turns dark for a few minutes). People in the penumbra see a partial eclipse.
• When the Moon is a bit far from Earth and looks smaller than the Sun, a bright ring shows. This is an annular eclipse.
• Safety: never look straight at the Sun, even during an eclipse. Use special eclipse glasses or a pinhole projector.

4. Lunar Eclipse

A lunar eclipse happens when the Earth passes between the Sun and the Moon, so the Moon moves into the Earth’s shadow.

• Order: Sun, Earth, Moon.
• It happens at full moon.
• The Moon may look dim or reddish. It is safe to look at with the eyes.
• It can be seen from anywhere on the night side of the Earth.

Why not every month? The Moon’s path is tilted about 5 degrees to the Earth’s path around the Sun, so the three bodies seldom line up exactly.

5. Ocean Tides

Tides are the regular rise and fall of the sea level. They are caused mainly by the gravitational pull of the Moon, and in part by the Sun.

• The Moon pulls the water on the side of the Earth facing it, causing a high tide there. A second bulge forms on the opposite side. So most places have two high tides and two low tides each day, about 12 hours 25 minutes apart.
• Spring tides: at new moon and full moon, the Sun, Earth and Moon line up and their pulls add. The tides are highest and lowest.
• Neap tides: at first and last quarter moon, the Sun and Moon pull at right angles. The tides have the smallest range.

Fishermen on the coast of Ghana, harbours and ships use tide timetables.

6. Satellites

A satellite is an object that orbits a larger body. The Moon is a natural satellite. Artificial satellites are made by people and launched by rockets.

• Uses: communication (TV, phone, internet), weather forecasts, GPS navigation, mapping farmland and forests, and science.
• Ghana’s first satellite, GhanaSat-1, was built by students of All Nations University and launched in 2017.

Remember: Solar eclipse: Moon in the middle. Lunar eclipse: Earth in the middle. Spring tides come with new and full moon.

Education Always (education.inspiringalways.com). Original notes written to follow the NaCCA Basic 9 Integrated Science curriculum.