Earth and Space – JSS1 Basic Science Lesson Note (Third Term)

The solar system is the sun and all the bodies that orbit it. These include the eight planets and their moons, asteroids, comets and meteoroids. The planets rotate about their axes and revolve around the sun. This lesson also covers the Earth, the sun, the moon, eclipses, climate and seasons.

Behavioural objectives

By the end of the lesson, students should be able to:

• describe the solar system and name the planets in order from the sun;
• explain rotation and revolution and state what each one causes;
• state the main facts about the Earth, the sun and the moon;
• explain the two types of eclipse;
• define climate and explain how seasons occur.

What is the solar system?

The sun and all the bodies orbiting around it make up the solar system. The planets and their moons are the main bodies that revolve around the sun.

Other bodies in the solar system are asteroids, comets and meteoroids.

What are the planets of the solar system?

Nearest to the sun is Mercury, the smallest of the planets. Then come Venus, Earth, Mars, Jupiter (the biggest planet), Saturn, Uranus and Neptune. Pluto was once counted as the ninth planet, but it is now classed as a dwarf planet. The distance across the solar system is about 12,000 million kilometres.

The planets in order from the sun are:

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

What are rotation and revolution?

Rotation: This is the movement of a planet about its axis. The rotation of the earth brings about night and day.

Revolution: This is the movement of a planet around the sun in the solar system. The Earth revolves around the sun, giving rise to seasons. The earth takes approximately 365 days to revolve around the sun.

What are the main facts about the Earth?

The Earth is the third planet from the sun. It is the only known planet in the universe that harbours living things. The Earth contains water which, in addition to oxygen, helps to support life.

The earth does not produce light, so it is said to be non-luminous. Heavenly bodies that give out light, such as the stars and the sun, are said to be luminous.

The Earth has only one satellite, called the Moon. The moon revolves around the Earth. The earth rotates about its axis, giving rise to day and night.

What are the main facts about the sun?

The sun is a star at the centre of the solar system. It supplies light and heat to all the planets. The sun rotates about its axis. The Earth revolves around the sun, giving rise to seasons, and takes approximately 365 days to do so. There is no water on the sun.

What are the main facts about the moon?

The moon is the Earth’s only natural satellite. It rotates about its axis and revolves around the Earth. The moon reflects light from the sun and supplies the earth with moonlight. The moon is non-luminous and has no life on it.

What is an eclipse?

An eclipse is the full or partial blocking of light from one celestial body by another celestial body.

Types of eclipse

1. Eclipse of the sun: This occurs when the moon moves between the sun and the earth and all three are exactly in a straight line.
2. Eclipse of the moon: This occurs when the earth is between the sun and the moon and the three are exactly in a straight line.

Note: There is no such thing as an eclipse of the earth.

What are climate and seasons?

Climate is the average weather condition of a particular area over a given period.

Seasons: The revolving of the earth about the sun gives rise to seasons. Different parts of the surface of the earth have the sun shining on them at different times of the year.

During some months of the year the days are shorter and the nights longer. During other months the nights are shorter and the days longer. There are also months when the days and nights are equal in length.

This happens because the Earth moves in an orbit around the sun. The earth tilts in opposite directions twice a year, which gives rise to two seasons: the rainy season and the dry season.

Evaluation

1. What is a solar system?
2. How many planets do we have? Mention them.
3. What is climate?
4. What is the difference between rotation and revolution?

Assignment

1. Define an eclipse and explain how an eclipse of the sun occurs.
2. Explain how an eclipse of the moon occurs.
3. State two facts about the moon.