GeographyICSE Class 9 · Rotation and Revolution

Rotation, Revolution, Day and Night and the Seasons (ICSE Class 9 Geography)

Updated 17 October 2026 · Draft, not yet fact-checked

Rotation is the spinning of the earth on its axis from west to east in about 24 hours, causing day and night. Revolution is the movement of the earth around the sun in about 365 days (365¼); because the axis is tilted 23½ degrees from the vertical and keeps its direction, the length of day and night varies and the seasons occur, with solstices on 21 June and 22 December and equinoxes on 21 March and 23 September.

Understand Rotation, Revolution, Day and Night and the Seasons

1. Rotation. The earth spins about its axis (an imaginary line through the poles) from west to east, completing one rotation in about 24 hours. Its speed is greatest at the equator (about 1,670 km/h, rounded) and zero at the poles. Effects: day and night, sunrise in the east, differences in time with longitude, and *Coriolis effect* (winds and currents deflected to the right in the northern and to the left in the southern hemisphere).

2. Revolution. The earth moves round the sun in an elliptical orbit in about 365¼ days. The extra quarter day adds one day every four years, giving a *leap year* of 366 days.

3. Inclined axis. The axis is tilted 23½ degrees from the perpendicular to the orbital plane (so it makes 66½ degrees with the plane) and always points in the same direction (towards the Pole Star).

4. Variation in day and night. As the earth revolves, the sun's vertical rays move between the Tropic of Cancer and Capricorn. In the summer of a hemisphere days are longer than nights and the sun's rays are more direct; in winter days are shorter.

5. Positions in the orbit.

*21 June (summer solstice, northern hemisphere)*: vertical rays on the Tropic of Cancer; the longest day in the north; midnight sun inside the Arctic Circle.
*22 December (winter solstice, northern hemisphere)*: vertical rays on the Tropic of Capricorn; the shortest day in the north.
*21 March and 23 September (equinoxes)*: vertical rays on the equator; day and night are equal everywhere.

6. Seasons. Spring, summer, autumn and winter in the temperate zones result from the changing angle of the sun's rays and the length of the day. Seasons are reversed in the two hemispheres.

Rotation, Revolution, Day and Night and the Seasons: key facts

Motion: Rotation: west to east, about 24 hours | Revolution: about 365.25 days
Axis: Tilt 23.5 degrees from the vertical | Points towards the Pole Star
Solstices: 21 June: sun over Tropic of Cancer | 22 December: sun over Tropic of Capricorn
Equinoxes: 21 March
23 September
Sun over equator
Equal day and night

Rotation, Revolution, Day and Night and the Seasons in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Different clock for a family abroad

Suppose a family in Kolkata is having breakfast at 7:30 a.m. when they call relatives in Brisbane and find that they are already having lunch, at about noon.

Which motion explains this?

Try it first, then show the solutionSolution

The earth rotates, so places in the east see the sun earlier.
Different longitudes have different times.

Answer: Rotation causes the time difference.

Memory hook: East sees sun first.

Tricks to remember Rotation, Revolution, Day and Night and the Seasons

Short memory aids. Say each one aloud once, then use it on a question the same day.

Rotation = Day, Revolution = Year
Rotation: day and night; revolution: seasons.
Use it when: Effects.
21-3-6-9-12
21 March, 21 June, 23 Sept, 22 Dec.
Use it when: Dates.

Rotation, Revolution, Day and Night and the Seasons: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Define · 2 marks · Short answerBoard level

Define rotation and revolution with the time taken by each. [2]

Try it first, then show the solutionSolution

Rotation: spinning on its axis in about 24 hours.
Revolution: orbit round the sun in about 365 and a quarter days.

Answer: Rotation: about 24 hours; revolution: about 365¼ days.

Example 2: Leap year · 3 marks · Short answerHarder board level

Why do we add one day in February in a leap year? Show the calculation. [3]

Try it first, then show the solutionSolution

The earth takes about 365¼ days to revolve.
Each year has 365 days, so ¼ day extra accumulates.
4 x ¼ = 1 day extra every four years.

Answer: ¼ day x 4 = 1 day, added as 29 February.

Example 3: Solstice reasoning · 3 marks · Short answerHarder board level

Explain why the sun appears overhead at the Tropic of Cancer on 21 June but never beyond it. [3]

Try it first, then show the solutionSolution

The axis is tilted 23½ degrees.
The sun's vertical rays can reach 23½ degrees N at most.
Beyond this the tilt prevents overhead rays.

Answer: Because of the 23½ degree tilt, the rays reach at most 23½ degrees N and S.

Example 4: If axis were vertical · 4 marks · Long answerHarder board level

If the earth's axis were perpendicular to the orbital plane, state three consequences. [4]

Try it first, then show the solutionSolution

No change in the sun's vertical position.
Day and night equal everywhere throughout the year.
No seasons; each latitude would have a nearly constant climate.
Poles would always receive slanting rays.

Answer: No seasons, equal day and night and constant climate for each latitude.

Example 5: Case: midnight sun · 6 marks · Case-basedHOTS / competency

Case. A traveller in northern Norway sees the sun above the horizon at midnight in June. (i) Name the phenomenon. [1] (ii) Which date is near? [1] (iii) Why does it occur? [2] (iv) What happens in December there? [2]

Try it first, then show the solutionSolution

(i) Midnight sun.
(ii) 21 June.
(iii) The north pole is tilted toward the sun, so the Arctic area has continuous daylight.
(iv) Polar night: the sun stays below the horizon.

Answer: (i) Midnight sun (ii) 21 June (iii) North tilted toward the sun (iv) Polar night.

Where students lose marks in Rotation, Revolution, Day and Night and the Seasons

The slips examiners see most often, and what to write instead.

Mistake: Writing that seasons occur because of distance from the sun
Common error.
Do this: Seasons occur due to tilt and revolution.
Usually costs: 2 marks.
Mistake: Reversing rotation direction
East-west confusion.
Do this: West to east.
Usually costs: 1 mark.
Mistake: Mixing solstice and equinox dates
Four dates swapped.
Do this: Learn 21 Mar, 21 Jun, 23 Sep, 22 Dec.
Usually costs: 1 mark.

Exam tips

Draw the orbit with the four positions and the tilted axis.
State the vertical rays position for each date.
Link every effect to the correct motion.
Show the leap-year calculation.

Practice questions on Rotation, Revolution, Day and Night and the Seasons

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
An observer in Kolkata sees the sun rise before an observer in Mumbai because the earth:
(a) rotates from east to west
(b) rotates from west to east
(c) revolves from east to west
(d) is tilted towards Kolkata
Hint
Sun rises in east.
Answer
(b) rotates from west to east.
Q2 · 2 marks · Very short answerBoard level
Name the two equinox dates. [2]
Hint
Spring/autumn.
Answer
21 March and 23 September.
Q3 · 1 mark · Very short answerBoard level
What is the angle of tilt of the earth's axis from the vertical? [1]
Hint
Number.
Answer
23½ degrees.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Days and nights are equal on the equinoxes.
Reason (R): The sun's vertical rays fall on the equator.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Circle of illumination.
Answer
(a).
Q5 · 3 marks · Short answerHarder board level
Differentiate rotation from revolution on two points. [3]
Hint
Effects.
Answer
Rotation: about 24 hours on the axis, causes day and night; revolution: about 365¼ days round the sun, causes seasons.
Q6 · 2 marks · Very short answerBoard level
Why does the speed of rotation decrease from equator to poles? [2]
Hint
Radius.
Answer
Places near the equator travel a larger circle in the same time; at the poles the circle shrinks to a point.
Q7 · 3 marks · Short answerHarder board level
Explain why summer days in a country at 50 degrees N are longer than in a country at the equator. [3]
Hint
Tilt.
Answer
Due to the tilt, the northern hemisphere in summer has a longer arc of day, while at the equator day and night stay near 12 hours.
Q8 · 3 marks · Short answerHarder board level
A cyclone-forming wind is heading due south in each hemisphere. Say which way rotation deflects it in each and name the effect. [3]
Hint
Right/left.
Answer
Rotation deflects moving air to the right in the northern hemisphere and to the left in the southern hemisphere. This is the Coriolis effect (Ferrel's law), caused by the earth's rotation.
Q9 · 4 marks · Case-basedHOTS / competency
Case. On 22 December a city in Australia has a long, warm day. (i) Which hemisphere is tilted toward the sun then? [1] (ii) Name the season in Australia. [1] (iii) Explain why it is winter in Canada. [2]
Hint
South.
Answer
(i) Southern. (ii) Summer. (iii) Canada is in the northern hemisphere tilted away; it gets slanting rays and short days.
Q10 · 3 marks · Long answerHOTS / competency
Case. A student claims that seasons occur because the earth is closer to the sun in summer. Refute with two points. [3]
Hint
Both hemispheres.
Answer
The two hemispheres have opposite seasons at the same time, which cannot happen if distance were the cause; the true cause is the tilt and revolution.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Direction of rotation?Show answer
West to east.
2.Leap year days?Show answer
366.
3.Date of summer solstice (north)?Show answer
21 June.
4.Tilt of axis?Show answer
23½ degrees.
5.Cause of seasons?Show answer
Tilted axis and revolution.

Rotation, Revolution, Day and Night and the Seasons: frequently asked questions

Is the orbit circular?

No, it is slightly elliptical.

Which star does the axis point to?

The Pole Star.

Why do poles have long nights?

Due to the tilt of the axis.