The Earth in the Solar System

Q21. Which planets have rings around them?

Ans. Jupiter, Saturn and Uranus have rings around them. These are belts of small debris.

Q22. What does the word planet mean?

Ans. The word ‘planet’ comes from the Greek word “Planetai” which means ‘wanderers’.

Q23. How do people used to determine direction in ancient times?

Ans. In ancient times, people used to determine directions during the night with the help of stars.

Q24. What do scientists hypothesize about the formation of the asteroids?

Ans. Scientists are of the view that asteroids are parts of a planet which exploded many years back.

Q25. What are meteoroids?

Ans. The small pieces of rocks which move around the sun are called meteoroids.

Q26. Who was the first man to step on the surface of the moon and when?

Ans. Neil Armstrong was the first man to step on the surface of the moon on 21 July 1969.

Q27. What is constellation? Write one example.

Ans. A group of stars forming a recognizable pattern is called constellation. Ursa Major or Big Bear is one such constellation.

Q28. Which is the most recognizable constellation?

Ans. One of the most easily recognizable constellations is the small bear or Saptarishi (Sapta-seven, rishi-sages).

Q29. Why can’t we see the moon and all those bright tiny objects during day time?

Ans. It is because the very bright light of the sun does not allow us to see all these bright objects of the night sky.

Q30. What are celestial bodies?

Ans. The sun, the moon and all those objects shining in the night sky are called celestial bodies.

Q31. Why earth appears blue from outer space?

Ans. From the outer space, the earth appears blue because its two-thirds surface is covered by water.

Q32. Why earth is called blue planet?

Ans. From the outer space, the earth appears blue because its two-thirds surface is covered by water.

Q33. Why Milky Way is called Akash Ganga?

Ans. In ancient India, it was imagined to be a river of light flowing in the sky. Thus, it was named Akash Ganga.

Q34. What is a satellite?

Ans. A Satellite is a celestial body that moves around the planets in the same way as the planets move around the sun.

Q35. Which planet is known as the “Earth’s Twin” and why?

Ans. Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.

Q36. What is the Universe?

Ans. A galaxy is a huge system of billions of stars, and clouds of dust and gases. There are millions of such galaxies that make the Universe.

Q37. What are orbits?

Ans. All the eight planets of the solar system move around the sun in fixed paths. These paths are elongated. They are called orbits.

Q38. Which is the nearest planet to the sun? How much time it takes to complete one round along its orbit?

Ans. Mercury is nearest to the sun. It takes only about 88 days to complete one round along its orbit.