Our Universe - 2 Class 3 Worksheet SST

Q1: Multiple-Choice Questions (MCQs)

(i) What is the name of the big group of stars, planets, and moons?
(a) Galaxy
(b) Universe
(c) Solar System
(d) Constellation
Ans: (a)
A galaxy is a large group of stars, planets, and other celestial objects held together by gravity.

(ii) Which planet is known as the "Red Planet"?

(a) Earth
(b) Venus
(c) Mars
(d) Jupiter
Ans: (c)
Mars is often called the "Red Planet" due to its reddish appearance caused by iron oxide on its surface.

(iii) What is the path that Earth takes around the Sun called?
(a) Route
(b) Orbit
(c) Journey
(d) Loop
Ans: (b)
An orbit is the path that a planet takes around its star, like Earth's path around the Sun.

(iv) Which celestial body is the closest to Earth?
(a) Mars
(b) Venus
(c) Jupiter
(d) Mercury
Ans: (d)
Mercury is the closest planet to the Sun and therefore closest to Earth.

(v) What is a shooting star also known as?
(a) Meteor
(b) Asteroid
(c) Comet
(d) Satellite
Ans: (a)
A shooting star is a meteoroid that burns up in Earth's atmosphere, creating a streak of light.

Q2: Fill in the Blanks

(i) The Sun is a __________ that provides light and warmth to Earth.
Ans: star
The Sun is a huge ball of hot, glowing gases and is classified as a star.

(ii) The Moon __________ around the Earth.
Ans: orbits
The Moon moves around the Earth in a path called an orbit due to the Earth's gravitational pull.

(iii) The __________ is the huge system of stars, planets, and other objects we see in the night sky.
Ans: universe
The universe encompasses all the galaxies, stars, planets, and other cosmic bodies.

(iv) The four inner planets of our Solar System are Mercury, Venus, __________, and Mars.
Ans: Earth
Earth is one of the four inner planets located closer to the Sun.

(v) The Milky Way is the name of our __________.
Ans: galaxy
The Milky Way is the spiral galaxy in which our Solar System resides.

Q3: True/False Questions

(i) The Sun is the largest planet in our Solar System.
Ans: False - The Sun is a star, not a planet, and it is much larger than any planet.

(ii) The Moon produces its own light.
Ans: False - The Moon does not produce its own light; it reflects the light of the Sun.

(iii) The Milky Way is the name of our Solar System.
Ans: False - The Milky Way is the name of the galaxy containing our Solar System.

(iv) Stars are hot balls of gas that produce their own light.
Ans: True - Stars generate light and heat through nuclear fusion in their cores.

(v) Earth orbits around the Moon.
Ans: False - The Moon orbits around Earth due to gravitational forces.

Q4: Answer the following questions

(i) What is the Big Bang theory, and why is it considered the most accepted explanation for the origin of the universe?
Ans: The Big Bang theory suggests that the universe began as a hot and dense point approximately 13.8 billion years ago and has been expanding ever since. It explains the origin of the universe from a massive explosion, leading to the formation of stars, galaxies, and other celestial bodies. This theory is widely accepted because it provides a coherent explanation for the observed cosmic background radiation, the abundance of light elements, and the large-scale structure of the universe.

(ii) Describe the significance of the Milky Way galaxy in the context of our Solar System.
Ans: The Milky Way galaxy is the home of our Solar System, including Earth and the Sun. It is a vast collection of stars, planets, and other celestial objects. The Milky Way provides the cosmic environment where Earth and the Solar System exist, and it is from within this galaxy that astronomers study various phenomena, deepening our understanding of the universe.

(iii) Explain why Earth is referred to as an "ocean planet" and what makes it unique in the Solar System.
Ans: Earth is called an "ocean planet" because a significant portion of its surface is covered by water. Oceans cover about 71% of Earth's surface, making it unique among the planets in our Solar System. This abundance of liquid water allows Earth to support a diverse range of life forms, making it the only known planet with ecosystems, oceans, and an atmosphere conducive to life.

(iv) What role do satellites play in the Solar System, and can you provide an example of a natural satellite?
Ans: Satellites in the Solar System are celestial bodies that revolve around planets. They play a crucial role in planetary dynamics, gravitational interactions, and scientific research. One prominent example of a natural satellite is the Moon, which orbits Earth. The Moon's gravitational influence affects Earth's tides and has significant scientific value, making it an essential component of Earth's celestial neighborhood.