The Earth in Space
Photo Credit: ThePlanets.org
- The word ‘solar’ is derived from the Latin word ‘solus’ which means ‘sun’.
- The solar system is made up of the sun and the nine planets, even though there is a disagreement about Pluto being a planet.
- These planets (from the nearest to the sun and moving outwards) are:
- Venus is the brightest planet.
- Pluto is the coldest planet.
- Mercury is the hottest because it is the nearest to the sun.
- All these planets revolve around the sun, each on its own orbit.
- This is the planet known to contain living things.
- It is made up of the lithosphere (solid part), the hydrosphere (part of the earth covered by water, like seas and oceans), and the atmosphere (gaseous envelope).
- The atmosphere is made up of these gases:
- Nitrogen (78.1% of dry air, by volume)
- Oxygen (20.95% of dry air, by volume)
- Carbon IV oxide (0.04% of dry air, by volume)
- Argon (0.93% of dry air, by volume)
- Water vapor (variable)
- Beyond the atmosphere, there is a space with no air or other matter. This space is called outer space.
Composition of the Earth
Layers of the Earth (Photo Credit: PhysicalGeography.net)
Movements of the Earth
- The earth carries out two types of movements:
- Rotation – This is the movement of the earth on its axis.
- Revolution – This is the movement of the earth along its orbit round the sun.
- The earth completes one rotation in 24 hours.
- The rotation of the earth causes day and night.
- The revolution of the earth brings about the seasons of the year.
Rotation and Revolution of the Earth (Photo Credit: Google.com)
Zones of the Atmosphere
Zones of the Atmosphere (Photo Credit: Scied.ucar.edu)
|Troposphere||The air is dense|
|Stratosphere||The air is less dense|
|Mesosphere||The air is thin|
|Ionosphere||Gas molecules are ionized|
Eclipse and Seasons of the Year
- The sun is a star at the center of our solar system.
- It is larger than the earth, and is made up of hot gases which produce a lot of heat and light.
- The light from the sun enables us to see on earth.
- Green plants also make use of the sun light to make their food through a process called photosynthesis.
- The warmth from the sun keeps plants and animals alive.
- The moon is the earth’s satellite, i.e., it always revolves round the earth.
- The moon’s surface is uneven and consists of hills and valleys called craters.
- There is no air and no life on the moon.
- The moon completes one revolution round the earth in 28 days. This period of 28 days is called one lunar month.
- The moon does not shine its own light. Moon light is actually sun light reflected from the surface of the moon.
- The changes observed in the sun lit parts of the moon at different times are called phases of the moon. These phases of the moon are:
- New moon.
- Quarter moon.
- Half moon.
- Three-quarter moon.
- Full moon.
- It is possible for the moon to shield or eclipse the earth from the sun because of the movements of the moon and the earth.
- There are two types of eclipses. They are:
- Eclipse of the Sun (Solar Eclipse): This happens when the moon moves in between the earth and the sun.
- Eclipse of the Moon (Lunar Eclipse): This happens when the earth comes between the sun and the moon so that the moon is in the shadow of the earth.
Lunar and Solar Eclipse (Photo Credit: Dyer Observatory)
Season of the Year
- The climate of a place is the typical weather condition of the place.
- A season is a period of time in the year which has distinctive characteristics, e.g. rainy season is when there is a lot of rain.
- The revolution of the earth causes the occurrence of seasons.
- As the earth moves around the sun, all parts of the earth do not receive the same number of sunshine at the same time. When the earth is in a particular part of the orbit round the sun, an area of the earth, say Europe, will have sunshine while the part opposite it may have total darkness.
- In the Northern and Southern zones of the earth, there are four seasons;
Seasons of Earth (Photo Credit: Enchantedlearning.com)
- In West Africa, there are only two seasons;
- Rainy season.
- Dry season.