What Causes Seasons – Teaching About Earth’s Tilt and Orbit

What causes seasons? The Earth rotates on its axis at a 23.5º angle from the Sun. When the Sun’s rays are more direct, it is warmer. Therefore, changes in the tilt cause it to be warmer during certain times of year. This causes seasons in some parts of the world. Take these simple steps to teach kids why we have spring, summer, fall, and winter.

Ms. Sneed Teaches About the Seasons

On September 21, our favorite fourth grade teacher dusted off her globe. Every year, she repeated the same lesson several times. “Repetition helps the reason for the seasons sink in,” she always said.

She walked over to her computer and pulled up dates of solstices and equinoxes.

Just then, the bell rang, and her students filed in. “Today,” she told them, “we’re going to take a trip around the Sun.”

Seasons and a Trip Around the Sun

Ms. Sneed looked at the student sitting in the middle of the classroom. “Cosmo,” she said, “you get to be the Sun.” Cosmo sat up straighter. Of course, everyone else giggled.

Then Ms. Sneed picked up the globe and walked to the front of the room. “I’m going to spin this globe and move it around the Sun,” she said. “This way, we will understand day and night, as well as the seasons a little better.”

Teach seasons with a globe.
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Rotation

“The Earth rotates, or spins on its axis, once every 24 hours. Do you see how the Sun (A.K.A. Cosmo) only shines on half of the Earth at a time? This causes day and night.” As she spoke, Ms. Sneed spun the globe around several times.

“So,” she asked, “why does the Sun rise in the east and set in the west?”

A girl in the front row raised her hand. “Because the Earth is spinning toward the east.”

Ms. Sneed nodded her head and continued. “If the Earth’s equator were lined up with the Sun, every day would have 12 hours of daylight and 12 hours of night. However, that is not the case.” Then she held the globe by its base so everyone could see that it was tilted.

Revolution

“Earth’s axis is tilted about 23.5º. Let’s see what happens as it revolves, or orbits the Sun, once every 365 days.”

The September Equinox Begins the Seasons of Fall (North) and Spring (South)

Ms. Sneed turned the globe so the north pole tilted toward the wall to her left. “Today,” she said, “marks the September equinox. On this day, the Sun (she pointed at Cosmo) shines its rays directly on the equator.” The teacher used a pencil to illustrate a ray from the Sun to the equator.

“On this day, the hemispheres receive equal sunlight. It marks the beginning of fall in the northern hemisphere and the beginning of spring in the southern.”

The December Solstice Begins the Seasons of Winter (North) and Summer (South)

Without explaining more, Ms. Sneed walked one-fourth of the way around the outside of the room. As she moved, she kept the globe positioned so that the north pole faced the same direction.

“Three months have passed,” she said. “Now it is December 21st. This marks the December solstice.” She tapped the north pole. “As you can see, the northern hemisphere now faces away from the Sun. Here, winter is just beginning. On the other hand, the southern hemisphere experiences the start of summer.”

Again, Ms. Sneed used her pencil to illustrate the Sun’s rays. “Now,” she said, “the Sun’s rays point directly at the Tropic of Capricorn. This is the farthest south the rays ever reach directly.”

Next, Ms. Sneed tilted her pencil toward the northern hemisphere. “It’s all about the angle. Direct rays are intense. Indirect rays, less so. Therefore, in December, the southern hemisphere receives more intense rays, and it is warmer there. Conversely, the northern hemisphere receives indirect rays, so it’s colder there.”

Once more, Ms. Sneed spun the globe around. “You can see that the southern hemisphere will also have longer days in December. However, this is not the reason for the seasons. Longer daylight does not equal warmer weather. Remember, it’s all about the angle.”

The Earth is tilted at an angle. Therefore, the Sun's rays hit Earth at different angles, causing seasons.
The March Equinox Begins the Seasons of Spring (North) and Fall (South)

Again, Ms. Sneed walked one-fourth of the way around the room. “Three more months have passed,” she said. “Now it’s March 21st.”

She pointed her pencil from Cosmo to the Earth. “And the Sun’s rays point directly at the equator again. Both hemispheres receive equal sunlight. However,” she said, “you can see that direct rays shine on the equator. Therefore, it’s warmest there. As the rays shine farther and farther north or south, they become less direct.” She tilted her pencil up and down to illustrate. “Hopefully, you’re beginning to see why the poles are so much colder than the equator.

“Anyway, this day marks the beginning of spring in the northern hemisphere, and the beginning of fall in the southern.”

The December Solstice Begins the Seasons of Summer (North) and Winter (South)

With no further ado, Ms. Sneed began walking again. When she was a quarter of the way around the room, she stopped. “Here we are at the June solstice,” she said. This time, she tapped the north pole. “Notice how the northern hemisphere faces toward the Sun.”

When she pointed her pencil from Cosmo to the globe, the point landed north of the equator. “On this day, the Sun’s rays fall directly on the Tropic of Cancer. Summer begins in the northern hemisphere, and winter begins in the southern.”

Reviewing the Reason for the Seasons

Finally, Ms. Sneed walked back to the front of the room. “Now we’ve traveled all the way around the Sun. You can see that we’re back at the September equinox.”

Next, she switched on the projector. A diagram of the equinoxes and solstices appeared. “Let’s review.”

As her students listened, Ms. Sneed summarized. “On or around December 20th, the Earth’s tilt causes direct sunlight to hit its southernmost point along the Tropic of Capricorn. At this time, the seasons change. Summer begins in the southern hemisphere, and winter begins in the northern hemisphere. From this point on, daylight hours in the northern hemisphere increase, and daylight hours in the southern hemisphere decrease.

“Six months later, on June 20th, the Earth’s tilt causes direct sunlight to hit its northernmost point along the Tropic of Cancer. At this time, summer begins in the northern hemisphere, and winter begins in the southern hemisphere.

“Halfway between each solstice, an equinox occurs. At that time, the Sun’s rays are directed on the equator.”

A diagram shows the solstices and equinoxes.

Learning About Climate Zones

Next, Ms. Sneed displayed a diagram of important lines of latitude. “Here we see the Tropic of Cancer at 23º north, Tropic of Capricorn at 23º south, and equator,” she said, pointing at each one. “This entire region is known as the Tropics. Because the Sun’s rays are most intense here, this is the warmest region on Earth.”

The teacher pointed to the north. “Inside the Arctic Circle, which begins at 66º north, the Sun does not set for at least one entire day in June. Conversely, inside the Antarctic Circle (66º south), it doesn’t set for at least one entire day in December. Because the Sun’s rays are so indirect in these regions, it remains cold.”

Next, Ms. Sneed pointed to the area between the Arctic Circle and Tropic of Cancer. “This,” she said, “is a temperate zone. That means it has seasons.”

Finally, she pointed to the region between the Antarctic Circle and the Tropic of Capricorn. “Same here.”

A diagram shows the equator, Tropic of Cancer, Tropic of Capricorn, Arctic and Antarctic Circles.

Students Apply What They’ve Learned About Seasons

At the December solstice, Ms. Sneed repeated her seasons performance.

In January and February, the class did more space science activities. Specifically, they focused on the relationships between the Earth, Sun, and Moon.

In one set of activities, they explored evidence of Earth’s revolution around the Sun. First, they experimented with shadows. Second, they explored how zodiac constellations change with the seasons. Third, the kids used sunrise and sunset tables to figure elapsed time and daylight hours.

Additionally, they built models of the solar system and studied phases of the Moon.

By the time of the March equinox, the concept of climate began to sink in. This time, she asked students to act out the Earth’s orbit around the Sun. Afterward, Ms. Sneed showed two videos:

Additionally, she used a set of articles to review.

Four articles reinforce concepts relating to the seasons.

Then she handed out a few seasons worksheets to formalize learning.

Two worksheets ask students to explain seasons and climate zones.

As her students quickly completed the pages, Ms. Sneed smiled. Sometimes, it took the entire year to really grasp an important space science concept. Repetition and making connections really helped.

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