Category : 4th Class
Our Earth and Universe
The universe is everything we can touch, feel, sense, measure or detect. It includes living things, plants, star, galaxies, dust clouds, light and even time.
The Sun and the eight planets with their moons make up the solar systems. The Sun is at the center of the solar system. All the planets and the smaller objects like comets, asteroids, meteorites, etc., revolve around the Sun.
The Sun is a star that emits heat and light. It is the largest member in the solar system. It gives sunlight. Plants need this sunlight to make their food using carbon dioxide, water, chlorophyll and minerals.
Mercury is the smallest planet in the solar system. It looks like our Moon. The surface of mercury is covered with craters. Though it is nearest to the Sun, it is less hotter than Venus. The reason is that the Mercury has no atmosphere to retain Sun's heat on it.
Venus is a very beautiful object in the sky. It is called the evening star. Venus is also the brightest and hotter planet because it has atmosphere containing more amount of carbon dioxide.
This is the only planet in the solar system that has life it. Earth looks blue from the space because water cover about 3/4th of the planet's surface. This is the only planet with an atmosphere containing oxygen.
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Mars is the fourth inner planet. Mars is blood red colour due to presence of iron oxides on it. There is sign of water and life on this planet.
It is the biggest planet of the solar system. There are strips on the surface of this planet, also a great red spot on its surface which can accommodate two Earths in it.
It is the second largest planet in the solar system, with rings along its equator. Rings are made up of dust and ice.
It is a blue planet because of the presence of methane its atmosphere. Uranus is also a giant planet. This is the only planet which was found by accident.
The size of the Neptune is smaller than that of the Uranus. Neptune is the last planet in the solar system Fast wind and storm blow across the planet. Neptune.
A satellite is an object in space that orbits or circles around a larger object. There are two kinds of satellites: such as the Moon or Artificial such as the national Space Station orbiting the Earth.
1. Natural Satellite
A small or secondary planet which revolves around larger one.
Types of natural satellites
There are two types of satellites in the solar system According to their orbits, they are divided into regular and irregular
i. Regular satellites
These are the ones that revolve around an object in the some sense with respect to the Sun. For example, the rotates from east to west and around the Earth means it is regular because it goes in synchrony.
ii. Irregular satellites
The orbits' irregular satellites are elliptical, very bent and away from their planets.
2. ARTIFICIAL SATELLITE
A man- made object placed in orbit around an astronomical body (usually the Earth).
Types of artificial satellites
The main division of its functions is organized in: research satellites, applications, navigation, meteorology and communication. Its purposes can be varied. Some of its types are:
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(i) Communication Satellite
They are employed in telecommunications, they provide signals for fast transmission with impact in the who planet. They process information from the source whoever receives it.
(ii) Navigation Satellite
One of the most commonly used is GPS (Global Positioning System). It transmits radio signals to show location through an electronic receiver.
(iii) Weather Satellite
They allow monitoring climatic changes and measuring the weather conditions of other planets.
They continually update atmospheric conditions and cob visualize storms, auroras, polluting effects, currents the seas, flows of energy and more.
(iv) Astronomical Satellites
They are used to take readings and observe distant galaxies.
EARTH AND ITS FEATURES
1. Our Earth is an interesting place where we live. We see high mountains, lush green valleys, deep oceans, sea, river, ponds, as well as vast desert.
2. Our earth is one of the eight planets that revolve around the Sun in the solar system. The largest planet in the solar system is Jupiter, smallest planet is Mercury. Brightest planet is Venus and the coldest planet is Neptune.
3. Earth is the fifth-largest planet in the solar system and the third-closest planet to the Sun. Earth is about 150 million kms away from the Sun. It is just at the right distance from the Sun, have water and a layer of air to sustain life.
4. The Earth seems flat to us and it is difficult to believe it is sphere in shape. Now it has been seen by astronauts from the space that Earth is round, flattened the top and swelled at the equator.
5. Rotation of the Earth
Spin bangle on any table top. Do you see any imaginary the spinning bangle? This imaginary line that we called axis.
The Earth also spins on its axis. This movement is called rotation The Earth spins from west to east and complete its one rotation in approximately 24 hours. We don't feel the spinning of Earth because everything including us along the Earth at the same speed. It is the Earth?s rotation that causes day and night.
6. Revolution of the Earth
The Earth rotates, it also moves around the Sun in a fixed path in which Earth moves around the sun is called orbit. Movement of the Earth around the sun in its fixed orbit is called revolution. Earth takes one complete one revolution. Earth is slightly tilted on Earth tilts and its movement around the Sun in fixed path causes seasons.
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