The Seasons Lesson: Definition, Causes & Earth’s Tilt

Lesson Overview

• What Are Seasons?
• Why Do We Have Seasons?
• Exploring Each Season
• Hemispheres and Opposite Seasons
• Day and Night
• Sunrise and Sunset
• Important Terms to Remember
• Effects of Seasons on Nature and Humans
• How Seasons Influence Daily Life

Have you noticed how the weather changes throughout the year? Sometimes it feels hot, while other times it becomes chilly and snowy. These differences in weather are due to seasons. In this lesson, we will explore what seasons are, why they happen, how they affect our planet, and their impact on everyday life.

What Are Seasons?

Seasons are specific times of the year characterized by distinct weather patterns, temperatures, and amounts of daylight. Most areas of the world experience four seasons:

• Spring
• Summer
• Autumn (Fall)
• Winter

Why Do We Have Seasons?

The primary reasons we experience seasons are Earth's tilt and its orbit around the Sun.

Earth's Tilt

The Earth is tilted at an angle of approximately 23.5 degrees on its axis, an imaginary line that passes through Earth's North and South Poles. This tilt is constant as Earth travels around the Sun. The tilt causes different parts of Earth to receive varying amounts of sunlight at different times of the year.

Revolution Around the Sun

Earth completes one full orbit, or revolution, around the Sun in about 365 days, which we call one year. As Earth moves around the Sun, its tilted position means sunlight hits Earth differently throughout the year, causing seasonal changes.

Check Your Understanding-Click to Begin the Quiz!

Earth's Seasons Quiz

Exploring Each Season

1. Spring

Spring happens when the Earth's tilt begins to bring your hemisphere closer to the Sun.

• Weather gets warmer.
• Plants start to bloom, trees grow leaves, and animals awaken from hibernation.
• Days become longer and brighter.

2. Summer

Summer is the season when your hemisphere is tilted closest toward the Sun.

• It's the warmest season with long days.
• Plants grow abundantly, animals are very active, and people enjoy outdoor activities.
• This season typically sees increased rainfall and thunderstorms in some areas.

3. Autumn (Fall)

Autumn occurs when the Earth's tilt starts moving away from the Sun.

• Days become shorter, temperatures cool down, and leaves change colors before falling.
• Animals prepare for winter by collecting food or migrating.
• Many plants slow their growth or become dormant.

4. Winter

Winter is when your hemisphere is tilted furthest away from the Sun.

• It's the coldest season, with short days and long nights.
• Many regions experience snowfall, frost, and freezing temperatures.
• Animals often hibernate or migrate, and plants remain dormant.

Hemispheres and Opposite Seasons

Earth is divided into two hemispheres:

• Northern Hemisphere: The top half of Earth (North America, Europe, Asia).
• Southern Hemisphere: The bottom half (Australia, southern Africa, South America, Antarctica).

Seasons are opposite in these hemispheres. When it is summer in the Northern Hemisphere, it's winter in the Southern Hemisphere. This happens because of Earth's tilt relative to the Sun.

Day and Night

Earth rotates, or spins, on its axis, causing day and night. This rotation takes 24 hours. When your part of Earth faces the Sun, it's daytime; when it faces away, it's nighttime.

Sunrise and Sunset

The Sun appears to rise in the east and set in the west due to Earth's rotation. However, this is called apparent motion because it's Earth spinning, not the Sun moving.

Important Terms to Remember

• Axis: An imaginary line Earth spins around.
• Revolve: Move around another object; Earth revolves around the Sun.
• Rotate: Spin around a central point; Earth rotates on its axis.
• Equator: Imaginary line around Earth's middle dividing it into hemispheres.

Effects of Seasons on Nature and Humans

Seasons affect all living things:

• Animals: Migration, hibernation, and adaptation to temperature changes.
• Plants: Growth cycles depend heavily on seasonal patterns.
• Humans: Seasonal changes affect farming, clothing, food availability, and daily activities.

How Seasons Influence Daily Life

• Clothing Choices: People wear lighter clothing in summer and warmer layers in winter.
• Food and Farming: Different seasons allow for the growing of specific fruits and vegetables.
• Activities: Each season offers unique outdoor activities, such as swimming in summer or skiing in winter.

Ready to Challenge Yourself? Start the Quiz!

The Seasons - Science Test Thursday, November 10, 2011