NCERT 8th Class (CBSE) Science: The Universe

Question: How is an artificial satellite different from a natural satellite? Give one example of each.

Answer: A celestial object that revolves around a planet is known as a natural satellite or moon of the planet. Example: The moon is the natural satellite of the earth. Whereas artificial satellites are man-made machines which are sent from the earth to get help in communication, weather forecasting, etc. Examples: Aryabhata, Bhaskara, Rohini, INSAT-1B, APPLE, etc.

Question: Describe the physical features of the Moon.

Answer: The Moon is dry and barren with no atmosphere. Its surface is covered with several craters and mountains.

Question: Give four ways in which stars are different from planets.

Answer: Stars are different from planets in the following ways:

Question: What major factors have enabled life to evolve and survive on the Earth?

Answer: All the factors necessary for life are present only on Earth.

1. It has an atmosphere containing the gases, oxygen and carbon dioxide, which are necessary for life.
2. It has water in liquid form, which is essential for life.
3. Being at the right distance from the sun, it is not as hot as Mercury or Venus, nor is it as cold as the planets which are further away.

Question: Give five ways in which artificial satellites are useful to us.

Answer: Artificial satellites are very useful to us.

1. They help in television and radio transmission.
2. They help in telephone communication.
3. They help us to study and forecast the weather by sending cloud pictures to the earth, taken from space.
4. They help in locating minerals.
5. They help in studying agricultural yield on the earth by photographing from above.