LEARN · PRACTISE · DISCOVER
The Universe, Solar System and Shape of the Earth
EVS Social Studies in Paper I(A) begins with the place where all human life happens: the Earth and its place in the universe. This lesson covers the shape of the Earth, the universe (its origin), the solar system, celestial bodies and constellations. Children’s natural curiosity about the night sky makes this an exciting topic to teach, and APTET questions here are short and factual.
The universe and the solar system
The universe is everything that exists: all space, matter and energy. Most scientists explain its origin by the Big Bang theory, which says it began expanding from an extremely hot, dense state about 13.8 billion years ago.
A galaxy is a huge system of billions of stars, gas and dust. Our galaxy is the Milky Way (Akash Ganga). Distances between stars are measured in light years: the distance light travels in one year. The Sun is a star, the nearest star to the Earth; light from the Sun takes about 8 minutes to reach us. The next nearest star, Proxima Centauri, is about 4.2 light years away.
The solar system is the Sun and everything that revolves around it: eight planets, dwarf planets, moons, asteroids, comets and meteoroids. The Sun’s gravity holds the system together.
| Planet (in order from the Sun) | Key facts |
|---|---|
| Mercury | closest to the Sun; smallest planet; shortest year (88 days); no moon |
| Venus | hottest planet (thick carbon dioxide atmosphere traps heat); brightest planet, seen as the “morning star” or “evening star”; rotates in the opposite direction to most planets; no moon |
| Earth | the “blue planet”; the only planet known to support life; one moon |
| Mars | the “red planet” (iron oxide in its soil); two small moons |
| Jupiter | largest planet; a gas giant with many moons |
| Saturn | famous for its bright rings |
| Uranus | rotates lying almost on its side |
| Neptune | farthest planet from the Sun |
Memory aid for the order: “My Very Efficient Mother Just Served Us Nuts.”
The first four planets are inner (terrestrial, rocky) planets; the last four are outer planets (gas and ice giants). Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union.
Other celestial bodies
| Body | Description |
|---|---|
| Moon | the Earth’s natural satellite, about 3,84,400 km away; it takes about 27 days to go round the Earth, so the same side always faces us; it shines by reflected sunlight and shows phases |
| Asteroids | rocky pieces orbiting the Sun, mostly in the asteroid belt between Mars and Jupiter |
| Comets | bodies of ice and dust; near the Sun they form a glowing tail that points away from the Sun; Halley’s comet appears about every 76 years |
| Meteors and meteorites | small pieces of rock that burn up in the air as “shooting stars“; those that reach the ground are meteorites |
| Artificial satellites | human-made objects orbiting the Earth for communication, weather and mapping; India’s first satellite was Aryabhata (1975) |
India’s rockets are launched from the Satish Dhawan Space Centre, Sriharikota, in Andhra Pradesh. Chandrayaan-3 landed near the Moon’s south pole on 23 August 2023, a day now celebrated as National Space Day.
Constellations and the Pole Star
A constellation is a group of stars that forms a recognisable pattern in the sky.
| Constellation | Notes |
|---|---|
| Ursa Major (Great Bear; Saptarishi in India) | seven bright stars look like a ladle or “Big Dipper”; two pointer stars point towards the Pole Star |
| Orion (the Hunter; Mriga) | visible in winter evenings; three stars in a row form the “belt” |
| Cassiopeia | five bright stars in a W or M shape |
The Pole Star (Dhruva Tara) lies almost directly above the North Pole, so it appears fixed in the northern sky while other stars seem to move. Travellers used it to find the north.
Shape of the Earth
The Earth is not a perfect sphere: it is slightly flattened at the poles and bulging at the equator. This shape is called a geoid (“Earth-shaped”). Evidence that the Earth is round:
- when a ship sails away, its hull disappears before its mast;
- photographs taken from space;
- ships and aircraft can travel all the way round it (Magellan’s expedition, 1519–1522, completed the first voyage round the world);
- the Earth’s shadow on the Moon during a lunar eclipse is always curved.
Exam focus
- Largest planet Jupiter; smallest and closest Mercury; hottest Venus; red planet Mars.
- Pluto: dwarf planet since 2006.
- Asteroid belt: between Mars and Jupiter; comet tails point away from the Sun.
- Pole Star: found using the pointer stars of Ursa Major (Saptarishi).
- Earth’s shape: a geoid.
Example
Mrs Rajani asks Class 5 to observe the Moon at the same time every evening for two weeks and draw its shape in a “Moon diary”. In class, they arrange their drawings in order and discover the phases themselves. One child spots Venus near the Moon and the class finds out why it shines so brightly.
Key takeaways
- The universe began with the Big Bang about 13.8 billion years ago; our galaxy is the Milky Way.
- The solar system has the Sun, eight planets, dwarf planets, moons, asteroids, comets and meteoroids.
- Mercury is closest, Jupiter largest, Venus hottest and Mars the red planet; Pluto is a dwarf planet.
- The Moon is the Earth’s natural satellite; Aryabhata (1975) was India’s first artificial satellite.
- Constellations are star patterns; the Pole Star marks the north.
- The Earth is a geoid, slightly flattened at the poles.
Practice
- The largest planet of the solar system is:
- (A) Saturn
- (B) Jupiter
- (C) Earth
- (D) Neptune
- The planet closest to the Sun is:
- (A) Venus
- (B) Earth
- (C) Mars
- (D) Mercury
- The hottest planet of the solar system is:
- (A) Venus
- (B) Mercury
- (C) Mars
- (D) Jupiter
- The planet known as the “red planet” is:
- (A) Jupiter
- (B) Venus
- (C) Mars
- (D) Saturn
- Pluto was reclassified as a dwarf planet in:
- (A) 1930
- (B) 1986
- (C) 2006
- (D) 2016
- The Pole Star can be located with the help of the pointer stars of:
- (A) Ursa Major (Saptarishi)
- (B) Orion
- (C) Cassiopeia
- (D) Scorpio
- The asteroid belt lies between the orbits of:
- (A) Earth and Mars
- (B) Venus and Earth
- (C) Saturn and Uranus
- (D) Mars and Jupiter
- The shape of the Earth is best described as:
- (A) a perfect sphere
- (B) a geoid, slightly flattened at the poles
- (C) a flat disc
- (D) a cube
Answers and explanations (tap to show)
- (B) Jupiter is the largest planet.
- (D) Mercury is the closest to the Sun.
- (A) Venus is the hottest because its thick atmosphere traps heat, even though Mercury is closer to the Sun.
- (C) Iron oxide in its soil makes Mars look red.
- (C) The International Astronomical Union reclassified Pluto in 2006.
- (A) The two pointer stars of Saptarishi point towards the Pole Star.
- (D) Most asteroids orbit between Mars and Jupiter.
- (B) The Earth bulges at the equator and is flattened at the poles.