ScienceDay, night and seasons
How the spinning earth gives us day and night, and its tilted journey gives us seasons.
The sun seems to rise in the east, cross the sky and set in the west. For thousands of years people believed that the sun moved around the earth. In fact, it is the earth that moves. The earth has two movements, and each has a big effect on our lives.
Rotation: day and night
The earth spins like a top around an imaginary line that passes through the North Pole and the South Pole. This line is called its axis, and the spinning is called rotation. The earth completes one rotation in about 24 hours, which we call one day.
The earth is a ball, so the sun can light only half of it at a time. The half that faces the sun has day. The half that faces away has night. As the earth turns, places move from the dark half into the light, and we see the sun "rise". The earth spins from west to east, which is why the sun appears in the east first.
That is also why time is different in different countries. When it is noon in India, it is still early morning in England and already afternoon in Japan.
Revolution: the year
While it spins, the earth also travels around the sun along a fixed path called its orbit. This movement is called revolution. One full revolution takes about 365 days and 6 hours, which is one year. We count 365 days in a year, and the extra hours add up to one more day every fourth year. That year has 366 days and is called a leap year; the extra day is 29 February.
The tilt: seasons
Seasons do not happen because the earth is closer to or farther from the sun. They happen because the earth's axis is tilted, by about 23.5 degrees, and it stays tilted in the same direction all through its journey.
For part of the year, the northern half of the earth leans towards the sun. The sun's rays fall more directly there, the days are longer, and it is summer in the north. At the same time the southern half leans away and has winter. Six months later the earth is on the other side of the sun; now the south leans towards the sun and has summer, while the north has winter. That is why Christmas comes in summer in Australia.
In between come spring and autumn. India, because of its winds and its place on the globe, also has a rainy season, the monsoon.
In short
- Rotation (spinning, 24 hours) causes day and night.
- Revolution (going around the sun, about 365 days) makes a year.
- Revolution together with the tilt of the axis causes seasons.
Key terms
- Axis
- the imaginary line through the poles around which the earth spins
- Rotation
- the spinning of the earth on its axis
- Revolution
- the movement of the earth around the sun
- Orbit
- the path of the earth around the sun
- Leap year
- a year of 366 days, every fourth year
Try it yourself
In a dark room, shine a torch on a ball. Only half is lit. Mark a dot on the ball for your town and turn the ball slowly: the dot moves from "day" into "night" and back. Tilt the ball and carry it around the torch to see how the lit part changes.
Quick questions
Answer in your head or on paper first, then tap to check.
What causes day and night?
The rotation of the earth on its axis.
How long does the earth take to go once around the sun?
About 365 days and 6 hours.
Why do we have a leap year?
The extra 6 hours each year add up to one extra day every four years.
What causes seasons?
The tilt of the earth's axis together with its revolution around the sun.
This is a simple explanation to help you understand. For examinations, read the same chapter in your prescribed textbook. Last checked: 11 November 2026.