Lesson Plan - Get It!
Do you have different seasons where you live? Have you wondered why, and wondered why they return every year? Find out how that happens!
Seasonal changes bring temperature and precipitation changes.
The temperatures drop during the winter and rise in the summer. These changes are related to the movement of the earth around the sun.
Before you continue, did you check out the previous lesson in our Space Science series? If not, find it in the right-hand sidebar under Related Lessons.
It takes the earth about 365 days to orbit, or move around, the sun.
- What else do you know that takes 365 days?
A full calendar year is 365 days; this is another way we use the sun and the earth's movement to measure time.
- Do you recall how long it takes the earth to make a full rotation on its axis?
During this movement around the sun, the amount of sunlight hitting various areas on the earth's surface changes. As a result of the changing amounts of sunlight, the earth experiences different seasons.
You learned in the last Related Lesson that the earth rotates on an imaginary axis every 24 hours.
The tilt of the earth is 23.5 degrees. That means that an angle of 23.5 degrees exists between the imaginary axis and the vertical center of earth. The tilt is important because it changes the angle of sunlight, which impacts the length of our days. As the earth moves around the sun, the North Pole points towards the sun for half of the year, and then the South Pole points towards the sun for the remaining six months.
When the North Pole points towards the sun, it is summer in the Northern Hemisphere and winter in the Southern Hemisphere. This means that the days in the North are longer. As the earth moves, the South Pole tilts towards the sun, causing the seasons to change in both hemispheres.
The longest day in the Northern Hemisphere occurs on June 21st (the first day of summer), with the longest night falling on December 21st (the first day of winter).
- What do you think the longest day in the Southern Hemisphere is?
It's the opposite: December 21st has the most sunlight, while June 21st has the longest night!
Here is an interesting fact: during summer in the United States, we are tilted towards the sun but are the farthest away from the sun! During winter, we are the closest to the sun but tilted away. So, distance to the sun does not impact seasons or temperatures; it is all about the tilt!
Check out Seasons and the Sun: Crash Course Kids 11.1 to review the reason for the seasons!
- If we are experiencing summer in the United States, what season is it in Brazil (located in the Southern Hemisphere)?
It's winter, with shorter days and lower temperatures. This difference is due to the earth's revolution along its orbit around the sun. As we move, the amount of sunlight changes, causing seasonal differences in temperature and precipitation.
In the Got It? section, you will learn more about the changes we observe on the surface of earth during seasonal changes.