What Causes Seasons? Earth's Tilt and Orbit

A landscape photo with four vertical filters, each representing a different season — Earth's seasons are a result of the planet's orbit and axial tilt. John Lamb / Getty Images

It turns out that the elliptical orbit of the Earth has little effect on the seasons. Instead, it is the 23.45-degree tilt of the planet's rotational axis that causes us to have winter and summer.

Have you ever paused to wonder, "What causes seasons?" As you feel the cool breeze of fall or the warmth of summer, it might seem like a simple question, but there's an interesting bit of science behind it. Let's unravel the intricate interplay of Earth's tilt and orbit and shed light on the reasons we experience seasons.

Contents

The Misconception: It's Not About Distance
Northern and Southern Hemispheres
Circling Back to Seasons

The Misconception: It's Not About Distance

Many believe that our changing seasons result from varying distances between Earth and the sun. While an understandable assumption, the truth is a bit more nuanced.

The main cause of our changing seasons is the Earth's axis. Imagine a straight line passing through Earth from the North Pole to the South Pole. This is the axis, and it's slightly tilted (by about 23.5 degrees, to be exact). Because of Earth's axial tilt, different parts of our planet get varying amounts of sunlight throughout the year as the Earth orbits the sun.

Another significant factor is the Earth's orbit. Earth doesn't just go around the sun in a perfect circle — it's more of an elliptical orbit. That means, at different times of the year, Earth is slightly closer or farther away from the sun. But remember, it's the tilt, not this distance, that's the major player in the changing seasons.

Northern and Southern Hemispheres

Here's a fun fact: While it's snowing and chilly in the Northern Hemisphere, our friends in the Southern Hemisphere might be hitting the beach. Why this drastic difference? The answer lies in how the sun's rays hit Earth.

As the Earth spins on its axis, one hemisphere leans toward the sun while the other leans away from the sun. When the Northern Hemisphere tilts towards our fiery star, it gets the sun's direct rays, leading to the toasty summer months. When it tilts away, the days grow shorter and colder, meaning the Southern Hemisphere experiences opposite seasons, with winter setting in when the north enjoys its summers and vice versa.

Ever heard of the summer solstice and winter solstice? These are the markers of the longest and shortest days of the year.

The summer solstice, in June, marks the day when the North Pole is tilted closest to the sun, while the winter solstice, in December, signifies when it's tilted furthest away. And the Southern Hemisphere has its solstices in reverse!

Circling Back to Seasons

So, as the Earth revolves in its orbit around the sun, combined with its axial tilt, different parts of the Earth's surface bask in varying intensities of the sun's rays. This results in the four seasons we're familiar with: spring, summer, autumn and winter.

The movement of our planet, combined with the sun's energy, are responsible for creating such rich and varied weather patterns.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.

Frequently Answered Questions

What are the causes of seasons?

Seasons are caused by the Earth's axial tilt and its orbital revolution around the sun. The Earth's axial tilt is responsible for the seasons we experience in the Northern and Southern hemispheres. The Earth's orbital revolution around the sun causes the seasons to change over the course of a year.