This science video lesson is designed for 6-12-year-old children. In this geography lesson, children learn about the rotation of the Earth and its shape.

This lesson also teaches the child what causes day and night, and the kinds of angles formed by sunlight when it falls on Earth.

## What is the Rotation of the Earth?

Earth is rotating around its axis (an imaginary straight line that extends from the North pole to the South pole). The Earth makes one complete rotation on its axis in 24 hours (1 day). While watching the sun, you notice that it moves across the sky, but it is actually the Earth that moves.

The Earth’s axis is tilted at an angle of 23 and one-half degrees and is perpendicular to the Earth’s orbit. This axial tilt causes the northern and southern hemispheres to lean away from the Sun. The rotation of the Earth divides it into two halves, one luminous and the other dark, resulting in day and night.

## Benefits of Earth’s Rotation

The rotation of the Earth has some benefits as follows:

• Because of the rotation of the earth, light, and darkness, temperature and humidity change throughout the day.
• Earth’s rotation also affects the tides in the oceans and seas.

## Revolution of the Earth

While rotating on its axis, the Earth moves around the Sun in a fixed path in an anticlockwise direction (east to west). This movement is called the Earth’s revolution. Earth makes one revolution around the Sun every year, or exactly in 365.242 days at a speed of 30 kilometers per second.

## What Causes Day and Night?

Due to the Earth’s rotation, sunlight reaches half of the Earth at any given moment. The side where sunlight falls is warmer and brighter, resulting in a day. On the other side of the Earth, the sun is hidden (it’s dark), so it’s cooler and darker, resulting in the night. Since the Earth is continuously rotating on its axis, we experience both day and night each day.

## What is the Shape of the Earth?

The shape of the Earth is a sphere or a geoid.

Earth appears as blue marble with swirls of white and areas of white, brown, yellow, and green from space.

• The blue color is water, which covers approx 71 percent of Earth’s surface.
• The white swirls are clouds.
• The brown, yellow, and green areas are land.
• The white areas are ice and snow.

Although our planet is a sphere, it is not a perfect sphere. Because of the gravitational force caused by the Earth’s rotation, the North and South Poles are slightly flat.

## Why is Earth’s Shape Changing?

Earth’s shape is constantly changing. The changes can be:

1. Periodic: can be seen daily tides that affect both the ocean and the crust;
2. Slow and steady: can be seen as the drift of tectonic plates or the rebound of the crust after a heavy sheet of ice has melted;
3. Violent: can be seen as events such as earthquakes, volcanic eruptions, or meteor strikes.

Watch the video to understand how angles of sun rays change when it falls on the Earth. The diagrams and pictorial illustrations are shown in the video allow the child to get a better understanding of the concept.