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School Social Studies Gap Book (Classes VI-X themes) · Chapter 1

Our Universe, Latitudes and Longitudes, Movements of the Earth, Maps

What to remember

  • The Earth is one planet of the Solar System, which is a small part of the Milky Way galaxy; its shape is a geoid (slightly flattened at the poles).
  • Latitudes are parallel circles measured north and south of the Equator (0°); longitudes are half-circles joining the poles, measured east and west of the Prime Meridian (0°, Greenwich). Every 1° of longitude equals 4 minutes of time.
  • Rotation (about 24 hours) gives day and night; revolution (about 365¼ days) together with the tilted axis gives seasons; a map is a reduced drawing of the Earth drawn to a scale, using direction, symbols and colours.

1. Our universe

The universe is all space, with all the matter and energy in it. A widely accepted explanation of its beginning is the Big Bang theory: the universe began from a very hot, dense point and has been expanding since then.

  • Galaxy: a huge group of stars, gas and dust held together by gravity. Our galaxy is the Milky Way, which is spiral in shape.
  • Star: a hot ball of gas that gives out its own heat and light. The Sun is the star at the centre of our Solar System.
  • Planet: a body that moves around a star and shines by reflected light. Satellite: a body that moves around a planet. The Moon is the natural satellite of the Earth.
  • Light year: a unit of distance, not of time. It is the distance light travels in one year (about 9.46 trillion km). Light from the Sun takes about 8 minutes to reach the Earth.

The Solar System has the Sun, eight planets, their satellites, dwarf planets, asteroids, comets and meteors. In order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. The four inner planets are rocky (terrestrial); the four outer planets are very large (Jupiter and Saturn are gas giants; Uranus and Neptune are ice giants). Pluto is a dwarf planet.

FeatureFacts
Nearest planet to the SunMercury
Largest planetJupiter
Planet with prominent ringsSaturn
Hottest planetVenus
Red planetMars
Planet where life is knownEarth (third from the Sun)

The Earth has water, a suitable temperature range and an atmosphere with oxygen; this is why it supports life. From space it looks blue because of its oceans, so it is called the Blue Planet. The Moon takes about 27 days to go round the Earth; its phases repeat in about 29½ days.

2. The globe: latitudes

A globe is a model of the Earth. It shows true shape, area and direction. Its axis is an imaginary line through the North and South Poles. It is tilted.

  • Equator (0° latitude): the largest parallel; it divides the Earth into the Northern and Southern Hemispheres.
  • Parallels of latitude: circles drawn parallel to the Equator. They become smaller toward the poles. The North Pole is 90°N and the South Pole is 90°S.
  • Important parallels: Tropic of Cancer (23½°N), Tropic of Capricorn (23½°S), Arctic Circle (66½°N), Antarctic Circle (66½°S).
  • Heat zones: the Torrid Zone lies between the two Tropics (most heat; the Sun can be overhead). The two Temperate Zones lie between a Tropic and a polar circle. The two Frigid Zones lie between a polar circle and a pole (least heat).
  • The Tropic of Cancer crosses India. It passes through eight states: Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram. Andhra Pradesh lies south of this line, wholly in the Torrid Zone.

3. The globe: longitudes and time

  • Meridians of longitude are half-circles from the North Pole to the South Pole. They are not parallel; they meet at the poles and are farthest apart at the Equator.
  • The Prime Meridian (0°) passes through Greenwich, near London. It divides the Earth into the Eastern Hemisphere and the Western Hemisphere. The opposite meridian is 180°, which is close to the International Date Line.
  • There are 360 degrees of longitude. The Earth turns 360° in 24 hours, so it turns 15° in one hour, or 1° in 4 minutes.
  • Places east of Greenwich are ahead of Greenwich Mean Time (GMT); places west are behind.
  • Local time is based on the Sun's position at noon. Using local time everywhere would be confusing, so each country adopts a Standard Time based on one central meridian.
  • Indian Standard Time (IST) is based on the 82½°E meridian, which passes near Mirzapur (Uttar Pradesh). IST is 5 hours 30 minutes ahead of GMT. India stretches over about 30° of longitude, so the east is about 2 hours ahead of the west in local sun time, but one standard time is used.
  • Worked example 1: 82½ × 4 = 330 minutes = 5 hours 30 minutes. This is how IST differs from GMT.
  • Worked example 2: When it is 12 noon at Greenwich, what is the time at 30°E? 30 × 4 = 120 minutes = 2 hours ahead, so 2 pm.
  • Worked example 3: At 60°W the time is 4 hours behind (60 × 4 = 240 minutes), so 8 am.
  • Crossing the International Date Line from west to east, a traveller repeats a day; from east to west, a day is skipped.

4. Movements of the Earth

MovementRotationRevolution
MeaningSpinning on its own axisMoving round the Sun in a fixed path (orbit)
DirectionWest to eastWest to east (anticlockwise seen from above the North Pole)
Time takenAbout 24 hoursAbout 365¼ days
ResultDay and night; apparent rising and setting of the Sun; tidesSeasons; change in length of day and night
  • Circle of illumination: the line that separates the lit half of the Earth from the dark half.
  • Leap year: the extra ¼ day each year adds to one full day every four years. A leap year has 366 days, and February has 29 days.
  • Tilt of the axis: the axis is tilted 23½° from the vertical, which means 66½° from the plane of the orbit. It always points toward the Pole Star in the same direction (the Earth's axis stays parallel to itself).
  • Seasons are caused by the tilt of the axis plus revolution. If the axis was not tilted, there would be no seasons.
Date (approx.)NameWhat happens
21 MarchSpring (vernal) equinoxSun's rays fall vertically on the Equator; day and night are nearly equal everywhere
21 JuneSummer solstice (Northern Hemisphere)Sun overhead at the Tropic of Cancer; longest day in the north
23 SeptemberAutumn equinoxSun overhead at the Equator; day and night equal
22 DecemberWinter solstice (Northern Hemisphere)Sun overhead at the Tropic of Capricorn; shortest day in the north

When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere. Near the poles there are weeks of continuous day or night in the year.

The Earth is nearest to the Sun (perihelion) in early January and farthest (aphelion) in early July. This does not cause the seasons; the tilt does.

Eclipses: A solar eclipse happens when the Moon comes between the Sun and the Earth (new moon). A lunar eclipse happens when the Earth comes between the Sun and the Moon (full moon).

5. Maps

A map is a drawing of the whole or part of the Earth on a flat surface, to a scale. A collection of maps is an atlas.

  • Types: Physical maps (relief, rivers, mountains); political maps (states, countries, capitals, boundaries); thematic maps (one theme, such as rainfall, soil, population or roads). Large-scale topographical sheets are made by the Survey of India.
  • Three components of a map: distance (scale), direction and symbols.
  • Scale: the ratio between a distance on the map and the real distance on the ground. It can be written in words (1 cm = 5 km), as a ratio or Representative Fraction (1:500,000), or as a line scale.
  • Large-scale map: shows a small area in much detail (for example a village or a town). Small-scale map: shows a large area with little detail (for example a country or the world).
  • Worked example: On a map of scale 1:50,000, 4 cm on the map is 4 × 50,000 = 200,000 cm = 2 km on the ground.
  • Direction: four cardinal points (north, south, east, west) and four intermediate points (NE, SE, SW, NW). A map normally has a north arrow.
  • Conventional symbols are small signs used for roads, railways, buildings, temples, wells and so on, explained in a key (legend).
  • Colours: blue for water; green for plains and vegetation; brown for hills and mountains; yellow for plateaus and deserts. These help to read relief quickly.
  • Contour lines join places of equal height above sea level. Close lines show a steep slope; wide lines show a gentle slope.
  • Sketch, plan and map: a sketch is a rough drawing without scale; a plan is a large-scale drawing of a small area, such as a house or a field; a map shows a bigger area.

Classroom angle: Use a globe and a torch to show day, night and seasons. Let children draw a sketch map of the school and the route from their home, and then give it a scale. Start from the known (their village) and move to the unknown (the country, the world). Teach the symbols with a simple key before showing the printed map.

Exam traps

  • 1. Light year is a unit of distance, not time.
  • 2. Rotation gives day and night; revolution gives seasons. Do not swap them.
  • 3. The tilt of the axis causes seasons, not the changing distance of the Earth from the Sun.
  • 4. The Equator is 0° latitude; the Prime Meridian is 0° longitude. Both are "zero lines" but are different circles.
  • 5. Latitudes are parallel to each other; longitudes are not parallel (they meet at the poles).
  • 6. Large-scale maps show small areas in more detail; small-scale maps show large areas.
  • 7. IST is based on 82½°E, not on Greenwich and not on 90°E.
  • 8. In the 21 June solstice the Sun is overhead at the Tropic of Cancer, while on 22 December it is overhead at the Tropic of Capricorn.

One-liners

  • 1. The Solar System has eight planets.
  • 2. Mercury is the nearest planet to the Sun and Jupiter is the largest.
  • 3. The Milky Way is our galaxy.
  • 4. The Moon is the Earth's only natural satellite.
  • 5. The Equator is 0° latitude and the poles are 90° north and south.
  • 6. The Prime Meridian passes through Greenwich.
  • 7. The Earth takes 4 minutes to turn through 1° of longitude.
  • 8. IST is 5 hours 30 minutes ahead of GMT.
  • 9. The Earth rotates from west to east.
  • 10. A leap year has 366 days.
  • 11. Equinoxes fall in March and September; solstices fall in June and December.
  • 12. The Survey of India prepares the official topographical maps of the country.

Practice questions

  1. Which galaxy contains our Solar System?

    1. Andromeda
    2. Sombrero
    3. Milky Way
    4. Whirlpool
    Answer

    C. Milky Way

    Our Solar System lies in the spiral Milky Way galaxy.

  2. A light year is a unit of

    1. speed
    2. brightness
    3. time
    4. distance
    Answer

    D. distance

    It is the distance light travels in one year.

  3. Which planet is nearest to the Sun?

    1. Earth
    2. Mercury
    3. Venus
    4. Mars
    Answer

    B. Mercury

    Mercury is the first planet from the Sun.

  4. Which is the largest planet of the Solar System?

    1. Jupiter
    2. Neptune
    3. Saturn
    4. Uranus
    Answer

    A. Jupiter

    Jupiter is the largest planet, a gas giant.

  5. The Earth is called the Blue Planet because

    1. it has no land
    2. a large part of its surface is covered by water
    3. it is nearest to the Sun
    4. its atmosphere is made of blue gas
    Answer

    B. a large part of its surface is covered by water

    Oceans make the Earth look blue from space.

  6. The parallel of latitude at 0° is called the

    1. Equator
    2. Arctic Circle
    3. Prime Meridian
    4. Tropic of Cancer
    Answer

    A. Equator

    The Equator is 0° latitude.

  7. The Prime Meridian passes through

    1. Cairo
    2. Mirzapur
    3. Paris
    4. Greenwich
    Answer

    D. Greenwich

    0° longitude passes through Greenwich near London.

  8. The Earth rotates in which direction?

    1. North to south
    2. East to west
    3. West to east
    4. South to north
    Answer

    C. West to east

    Rotation is from west to east, so the Sun appears to rise in the east.

  9. How many days does the Earth take to complete one revolution round the Sun?

    1. About 24 days
    2. About 360 days
    3. About 365¼ days
    4. About 30 days
    Answer

    C. About 365¼ days

    The extra quarter day gives the leap year.

  10. Indian Standard Time is based on the meridian of

    1. 97½°E
    2. 82½°E
    3. 68°E
    4. 90°E
    Answer

    B. 82½°E

    IST uses 82½°E, passing near Mirzapur.

  11. Day and night are caused by the Earth's

    1. revolution
    2. tilt only
    3. gravity
    4. rotation
    Answer

    D. rotation

    Rotation turns each place toward and away from the Sun every 24 hours.

  12. A map showing states, capitals and boundaries is a

    1. political map
    2. contour map
    3. thematic rainfall map
    4. physical map
    Answer

    A. political map

    Political maps show administrative divisions.

  13. The Tropic of Cancer is at

    1. 66½°N
    2. 23½°S
    3. 23½°N
    4. 0°
    Answer

    C. 23½°N

    It is 23½° north of the Equator.

  14. Which Indian state is NOT crossed by the Tropic of Cancer?

    1. Andhra Pradesh
    2. Mizoram
    3. Gujarat
    4. Chhattisgarh
    Answer

    A. Andhra Pradesh

    Andhra Pradesh lies south of the Tropic of Cancer.

  15. Representative Fraction 1:50,000 means 1 cm on the map equals

    1. 50 km on the ground
    2. 5 km on the ground
    3. 500 m on the ground
    4. 0.5 km on the ground
    Answer

    D. 0.5 km on the ground

    50,000 cm = 500 m = 0.5 km.

  16. The Earth turns through how many degrees of longitude in one hour?

    1. 30°
    2. 15°
    3. 1°
    4. 10°
    Answer

    B. 15°

    360° in 24 hours gives 15° per hour.

  17. When it is 12 noon at Greenwich, the time at 60°E is

    1. 4 pm
    2. 2 pm
    3. 6 pm
    4. 8 am
    Answer

    A. 4 pm

    60 × 4 = 240 minutes = 4 hours ahead, so 4 pm.

  18. When it is 12 noon at Greenwich, the time at 45°W is

    1. 3 pm
    2. 7 am
    3. 11 am
    4. 9 am
    Answer

    D. 9 am

    45 × 4 = 180 minutes = 3 hours behind, so 9 am.

  19. The time difference between IST and GMT is

    1. 4 hours 30 minutes
    2. 5 hours
    3. 5 hours 30 minutes
    4. 6 hours
    Answer

    C. 5 hours 30 minutes

    82½ × 4 minutes = 330 minutes.

  20. On 21 June the Sun's rays fall vertically on the

    1. Arctic Circle
    2. Tropic of Cancer
    3. Equator
    4. Tropic of Capricorn
    Answer

    B. Tropic of Cancer

    21 June is the summer solstice of the Northern Hemisphere.

  21. On 22 December the longest day occurs in the

    1. Northern Hemisphere
    2. Southern Hemisphere
    3. Equatorial region only
    4. Both hemispheres equally
    Answer

    B. Southern Hemisphere

    The Sun is overhead at the Tropic of Capricorn, so the south has its longest day.

  22. Seasons on the Earth are caused mainly by

    1. the Moon's pull
    2. rotation alone
    3. distance from the Sun alone
    4. the tilt of the axis and revolution
    Answer

    D. the tilt of the axis and revolution

    Tilt plus revolution changes the angle and length of sunlight.

  23. A solar eclipse occurs when

    1. the Sun comes between the Earth and the Moon
    2. the Earth comes between the Sun and the Moon
    3. the Moon comes between the Sun and the Earth
    4. the Moon is full
    Answer

    C. the Moon comes between the Sun and the Earth

    It happens at new moon when the Moon blocks sunlight.

  24. Which type of map would best show the plan of a village in great detail?

    1. Large-scale map
    2. Small-scale map
    3. World political map
    4. Globe
    Answer

    A. Large-scale map

    A large scale shows small areas in more detail.

  25. Contour lines drawn very close together show

    1. a water body
    2. a plain
    3. a gentle slope
    4. a steep slope
    Answer

    D. a steep slope

    Close lines mean height changes quickly.

  26. A class teacher wants children to understand day and night. The most suitable activity is to

    1. memorise a table
    2. rotate a globe in front of a torch
    3. read a definition aloud
    4. copy a diagram from the board
    Answer

    B. rotate a globe in front of a torch

    A concrete demonstration builds understanding from observation.

  27. Match the pair correctly: Torrid Zone

    1. Between the Arctic Circle and the North Pole
    2. Between the Tropic of Cancer and the Arctic Circle
    3. Between the Tropic of Cancer and the Tropic of Capricorn
    4. Between the Antarctic Circle and the South Pole
    Answer

    C. Between the Tropic of Cancer and the Tropic of Capricorn

    The Torrid Zone lies between the two Tropics.

  28. If a map has a scale of 1 cm = 10 km, a road 5 cm long on the map is actually

    1. 50 km
    2. 15 km
    3. 2 km
    4. 500 km
    Answer

    A. 50 km

    5 × 10 = 50 km.

  29. On a map of scale 1:100,000, two towns are 6 cm apart. Their real distance is

    1. 600 km
    2. 6 km
    3. 60 km
    4. 0.6 km
    Answer

    B. 6 km

    6 × 100,000 cm = 600,000 cm = 6 km.

  30. The Earth is nearest to the Sun in early January. This position is called

    1. equinox
    2. aphelion
    3. perihelion
    4. solstice
    Answer

    C. perihelion

    Perihelion is the nearest point; aphelion is the farthest.

  31. Between which two dates do the equinoxes occur?

    1. 21 June and 22 December
    2. 1 April and 1 October
    3. 14 January and 14 July
    4. 21 March and 23 September
    Answer

    D. 21 March and 23 September

    Day and night are equal on the equinoxes.

  32. Which of these is the correct order of planets from the Sun?

    1. Earth, Mars, Jupiter, Saturn
    2. Earth, Mars, Saturn, Jupiter
    3. Mars, Earth, Jupiter, Saturn
    4. Earth, Jupiter, Mars, Saturn
    Answer

    A. Earth, Mars, Jupiter, Saturn

    The order is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

  33. Consider the statements on the Earth's movements. 1. Revolution causes day and night. 2. Rotation takes about 24 hours.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Rotation causes day and night; revolution causes seasons.

  34. Consider the statements on latitudes and longitudes. 1. All parallels of latitude are equal in length. 2. All meridians of longitude meet at the poles.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Parallels become smaller towards the poles; meridians meet at the poles.

  35. Consider the statements on time. 1. Places west of Greenwich are ahead of GMT. 2. The Earth takes 4 minutes to turn 1° of longitude.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    West of Greenwich the time is behind GMT; east it is ahead.

  36. Consider the statements on maps. 1. A small-scale map shows a large area with less detail. 2. A large-scale map is always better for showing a country.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Large-scale maps are for small areas; small-scale maps show countries.

  37. Consider the statements on the Solar System. 1. The Moon is a planet. 2. Jupiter and Saturn are gas giants.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    The Moon is a natural satellite, not a planet.

  38. Consider the statements on India's location. 1. The Tropic of Cancer passes through Madhya Pradesh. 2. IST is based on a meridian that passes through Greenwich.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    IST uses 82½°E; the Prime Meridian passes through Greenwich.

  39. Consider the statements on the tilt of the Earth's axis. 1. The axis changes its direction to point to a different star every month. 2. The axis is tilted at 23½° from the vertical.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    The axis stays parallel to itself and points to the Pole Star.

  40. Consider the statements on eclipses. 1. A lunar eclipse takes place on a full moon day. 2. A solar eclipse takes place when the Earth lies between the Sun and the Moon.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    In a solar eclipse the Moon lies between the Sun and the Earth.

  41. Consider the statements on the International Date Line. 1. It passes through Greenwich. 2. It lies close to the 180° meridian.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Greenwich is 0°; the Date Line is near 180°.

  42. Consider the statements on map symbols and colours. 1. On physical maps brown commonly shows highlands. 2. A key explains the conventional symbols used in a map.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are standard map-reading facts.

  43. Consider the statements on equinox and solstice. 1. On equinoxes the Sun is overhead at the Equator. 2. On 21 June the day is longest in the Northern Hemisphere.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct for the Northern Hemisphere summer solstice and the equinoxes.

  44. Consider the statements on a light year and the Sun. 1. Light from the Sun reaches the Earth in about 8 minutes. 2. A light year is about one year of time.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    A light year is a distance, not a period of time.

  45. Consider the statements on contour lines. 1. Widely spaced contours show a steep slope. 2. Contour lines join places of equal height.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Widely spaced contours mean a gentle slope.

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