What is the main cause of the change of seasons on Earth?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Tilt of Earth's axis combined with revolution of the Earth
The Earth’s axis is tilted by about 23.5° and keeps pointing the same way in space while the Earth goes round the Sun. So, during the year, each hemisphere is turned towards the Sun for one half of the orbit and away from it for the other:
Turned towards the Sun, a hemisphere gets more direct rays and longer days: summer
Six months later, turned away, it gets slanting rays and shorter days: winter
A tilted Earth that did not go round the Sun would keep the same season all year, so the seasons come from the tilt and the revolution together.
Why the other options are incorrect
Option (1) Revolution of Earth around the Sun — Incorrect. Without the tilt, the Sun’s rays would fall the same way all year, so revolution alone gives no seasons.
Option (2) Rotation of Earth on its axis — Incorrect. Rotation, once in about 24 hours, causes day and night.
Option (3) Gravitational pull of the Moon — Incorrect. The Moon’s pull, with the Sun’s, causes the tides of the sea.