Patterns of Daily Change

Learning Objectives

By the end of this unit, you will be expected to understand Earth's rotation and its effects on daily life. You'll learn to describe how the Earth's rotation causes the Sun to appear to move across the sky, leading to our day and night cycle. You'll also understand how this rotation affects the changing shadows we see throughout the day.

You may not feel Earth spinning, or rotating, but it does…and fast!

© Rob Byron/Shutterstock.com

Lesson Summary

This lesson introduces you to the idea that Earth’s rotation causes patterns of daily change. Through videos, images, and text, you will learn that Earth’s rotation gives the Sun the appearance of motion and causes patterns of daily change, such as day and night, and changes in shadows.

As Earth rotates, the part that faces the Sun experiences daytime. For the other part, it is nighttime.

© NASA

Key Concepts

1. Earth's rotation is the continuous spinning of our planet around its axis, a cycle that takes roughly 24 hours and results in the sequence of day and night.

2. The Sun’s apparent movement from east to west during the day is not due to the Sun's movement but is a result of Earth's rotation, which alters our perspective of the Sun's position in the sky.

3. The rotation of the Earth not only influences the Sun's apparent position but also significantly impacts the shadows we observe, as their length and direction change throughout the day in response to the Sun’s shifting position.

As Earth rotates, the Sun moves through the sky, from sunrise to sunset.

Encyclopædia Britannica, Inc.

Background

What is Earth's rotation? It is a continuous movement of our planet spinning around an invisible line known as its axis. Think of it like a spinning top that never stops! This rotation takes approximately 24 hours to complete, creating the cycle of day and night that we experience.

Have you ever watched the Sun rise in the east and set in the west? While it seems like the Sun is moving across the sky, Earth’s rotation gives the Sun the appearance of motion. This is why we see the Sun in different positions at different times of the day.

Along with the Sun’s position changes, Earth's rotation also affects the shadows we see. As the position of the Sun changes due to Earth's rotation, shadows cast by the Sun also shift and change their length and direction. This is why your shadow looks different in the morning compared to the afternoon!

Notice how the shadows cast by a tree change throughout the day.

Encyclopædia Britannica, Inc.

Expedition Learn

Click on the image to begin your unit.