If you are looking for Tamil Nadu Board Class 6 Social Science Unit 1 The Universe and the Solar System then you are at the right place. Here we are providing solutions as well as additional QA / Important Notes.
Fill in the blanks
- The Universe was formed after…..explosion.[Big Bang]
- …….is the unit used to measure the distance between two celestial bodies.[Light Year]
- …….is the centre of the solar system.[Sun]
- The word planet means ……….[Wanderer]
- ……….planet has many natural satellites.[Jupiter]
- India’s first ever mission to the moon is …………[Chandrayaan-1]
- Earth is inclined by ………..degrees.[23.5]
- The Equator faces the Sun directly on……….and……………[March 21 & Sept. 23]
- At the time of Perihelion, the Earth is……….. to the Sun.[closest]
- The line which divides day and night on the Earth’s surface is …………[the Terminator Line]
Choose the best answer
The movement of the Earth on its axis is called
- Revolution
- Seasons
- Rotation
- Circulation
The Tropic of Capricorn faces the Sun directly on
- March 21
- June 21
- September 23
- December 22
The galaxy in which our solar system is found is
- Andromeda
- Magellanic clouds
- Milky Way
- Starburst
The only celestial body where man has successfully landed
- Mars
- Moon
- Mercury
- Venus
Which of the following planets can float on water?
- Jupiter
- Saturn
- Uranus
- Neptune
Circle the odd one out
- Venus, Jupiter, Neptune, Saturn [Venus is a terrestrial planet, the others are gas giants.]
- Sirius, Andromeda, Milky way,Magellanic clouds.[Andromeda, Milky Way, and Magellanic Clouds are galaxies, Sirius is a star.]
- Pluto, Eris, Ceres, Io [Io is a moon, the others are dwarf planets.]
- Comet, Asteroids, Meteorites, Dwarf planets [Dwarf planets are larger celestial bodies, the others are smaller objects.]
- Rover, Orbiter, Aeroplane, Space shuttle. [Aeroplane is not used for space exploration, the others are.]
Match the following
- Hottest Planet – a. Mars
- Ringed Planet – b. Neptune
- Red Planet – c. Venus
- Somersaulting Planet – d. Saturn
- Coldest Planet – e. Uranus
Answer
- Hottest Planet – c. Venus
Ringed Planet – d. Saturn
Red Planet – a. Mars
Somersaulting Planet – e. Uranus
Coldest Planet – b. Neptune
Consider the following statements
- Venus rotates from east to west.
- The Tropic of Cancer faces the Sun on June 21.
- Mars has rings around it.
Choose the correct answer using the codes given below.
- 1 and 2
- 2 and 3
- 1, 2 and 3
- 2 only
- ii) Which of the statement(s) is/are true?
Statement I: Earth is called a watery planet.
Statement II: The rotation of the Earth causes seasons.
- I is true; II is wrong
- I is wrong; II is true
- Both the statements are true
- Statements I and II are wrong.
Name the following
- Cluster of stars. [Galaxy]
- The nearest galaxy to the solar system.[Andromeda galaxy]
- The brightest planet.[Venus]
- The living sphere.[Biosphere]
- The year which has 366 days.[Leap Year]
Answer in brief
Name the inner planets.
The inner planets, also known as terrestrial planets, are Mercury, Venus, Earth, and Mars.
Pluto is no longer a planet. Reason out.
Pluto is no longer classified as a planet because it does not meet all the criteria set by the International Astronomical Union (IAU) in 2006. Specifically, Pluto has not cleared its neighboring region of other objects. It shares its orbit with other objects in the Kuiper Belt, thus failing the criterion of “clearing the neighborhood” around its orbit, which is essential for full planetary status. Therefore, Pluto is classified as a dwarf planet.
What is perihelion?
Perihelion is the point in the orbit of a planet or other celestial body where it is closest to the Sun. For Earth, perihelion occurs around January 3rd each year.
How many times in a year would you find the Sun overhead if you lived on 20°N Latitude?
If you lived on 20°N Latitude, you would find the Sun directly overhead twice a year. This occurs when the Sun’s declination is exactly 20°N, once during its northward movement (around late April) and once during its southward movement (around mid-August).
Which celestial body shares its orbit with others? Give an example.
Dwarf planets can share their orbits with other celestial bodies. An example is Pluto, which shares its orbit with objects in the Kuiper Belt.
Give reasons.
Why is Uranus called the somersaulting planet?
Uranus is called the somersaulting planet because of its unique axial tilt. Its axis is tilted by about 98 degrees, which means it essentially rotates on its side. This extreme tilt causes Uranus to appear as if it is rolling along its orbit around the Sun, unlike any other planet in the solar system.
The surface of the moon has many craters.
The surface of the moon has many craters because it lacks an atmosphere. Without an atmosphere, there is no air resistance to slow down or burn up meteoroids before they impact the surface. As a result, meteoroids and other space debris collide with the Moon’s surface directly, creating numerous craters over billions of years.
The velocity of the Earth’s rotation is zero at poles.
The velocity of the Earth’s rotation is zero at the poles because of the nature of rotational motion. At the poles, the rotational axis intersects the surface, so there is no lateral movement as the Earth spins. All points at the poles essentially stay in the same position while the Earth rotates around its axis. Conversely, at the equator, points on the surface travel the longest distance in a day, leading to the highest rotational velocity.
Answer in detail
Distinguish between inner and outer planets.
| Inner Planets (Terrestrial Planets) | Outer Planets (Jovian Planets) |
| Mercury, Venus, Earth, Mars | Jupiter, Saturn, Uranus, Neptune |
| Closer to the Sun | Farther from the Sun |
| Primarily composed of rock and metal | Primarily composed of gases and ices |
| Smaller in size | Larger in size |
| Solid, rocky surfaces | Gaseous with no well-defined solid surface |
| Thinner atmospheres | Thick atmospheres composed mainly of hydrogen and helium |
| Few or no natural satellites | Many natural satellites |
| No ring systems | Prominent ring systems (especially Saturn) |
| Higher temperatures due to proximity to the Sun | Lower temperatures due to distance from the Sun |
| Slower rotation | Faster rotation |
What are the effects of rotation and revolution?
Rotation:
Day and Night: The Earth’s rotation on its axis causes day and night. As the Earth rotates, different parts of its surface move into and out of the sunlight, creating a cycle of daylight and darkness approximately every 24 hours.
Coriolis Effect: The rotation of the Earth affects the movement of air and water masses, causing them to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This is known as the Coriolis effect and influences weather patterns and ocean currents.
Time Zones: The Earth’s rotation is divided into 24 time zones, each one roughly corresponding to 15 degrees of longitude. This system helps standardize time across different regions of the world.
Revolution:
Seasons: The Earth’s revolution around the Sun, combined with the tilt of its axis, causes the changing seasons. As the Earth orbits the Sun, different parts of the Earth receive varying amounts of sunlight throughout the year, resulting in seasonal changes.
Varying Day Lengths: The tilt of the Earth’s axis also causes variations in the length of day and night throughout the year. During summer, days are longer, and nights are shorter, while during winter, days are shorter, and nights are longer.
Equinoxes and Solstices: The Earth’s revolution leads to specific points in the year known as equinoxes (when day and night are equal) and solstices (the longest and shortest days of the year). These occur due to the tilt and position of the Earth in its orbit.
Explain the characteristics of the various spheres of the Earth.
Lithosphere:
The lithosphere is the solid, outermost layer of the Earth. It includes the crust and the upper part of the mantle.
It consists of various types of rocks and minerals and forms the continents and ocean floors.
The lithosphere is broken into tectonic plates that float on the semi-fluid asthenosphere below. The movement of these plates causes earthquakes, volcanic activity, and the formation of mountains.
Hydrosphere:
The hydrosphere encompasses all the water on Earth, including oceans, seas, rivers, lakes, glaciers, and water vapor in the atmosphere.
It covers about 71% of the Earth’s surface, with the vast majority of this water found in the oceans.
The hydrosphere plays a crucial role in regulating the Earth’s climate and weather patterns through the water cycle, which includes processes such as evaporation, condensation, precipitation, and runoff.
Atmosphere:
The atmosphere is the layer of gases surrounding the Earth. It is composed primarily of nitrogen (78%) and oxygen (21%), with traces of other gases like carbon dioxide, argon, and water vapor.
The atmosphere is divided into several layers based on temperature and composition: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
It protects life on Earth by absorbing harmful solar radiation, reducing temperature extremes between day and night, and providing essential gases for respiration and photosynthesis.
Biosphere:
The biosphere is the zone of life on Earth, where living organisms interact with the lithosphere, hydrosphere, and atmosphere.
It includes all ecosystems, from the deepest ocean trenches to the highest mountains, where life is possible.
The biosphere is characterized by the presence of life forms, including plants, animals, and microorganisms, which depend on and contribute to the cycling of nutrients and energy within their environments.
