What Causes the Seasons?



The landscape and weather change greatly during the year in regions that have four distinct seasons. Images Courtesy of Corel
Click on image for full size (161 KB JPEG)
The Earth's orbit is in the shape of an ellipse (a stretched out circle), so that sometimes the Earth is closer to the Sun than at other times. Is this the cause of the seasons?

You can imagine that if the seasons were caused by the Earth's orbit, people who live north of the Equator (in places like the North America, Europe and Asia) and people who live south of the equator (in places like South America, Australia, and Africa) would have the same seasons. For example, if winter occured because the Earth was far away from the Sun, everyplace on the Earth would be cold at the same time.

But this is not what happens! Summer in the north occurs at the same time as winter in the south, and vice-versa. It turns out that the Earth's orbit is nearly a perfect circle, and the difference between its smallest distance from the Sun and its largest distance is very small. In fact, the Earth is furthest away from the Sun in June when it is summer in the north!

The Earth is a very special planet in many ways. Just as Earth's unique atmosphere and its distance from the Sun work together to make Earth the right temperature to support life, Earth's orbit and its rotation work together to create the seasons.

When is the Earth farthest, closest to the Sun?

What Causes the Seasons?



The landscape and weather change greatly during the year in regions that have four distinct seasons. Images Courtesy of Corel
Click on image for full size (161 KB JPEG)
Let's get rid of some common misconceptions about the seasons. The Earth's orbit is in the shape of an ellipse, so that sometimes the Earth is a little bit closer to the Sun than at other times. Is this the cause of the seasons?

You can imagine that if the seasons were caused by the Earth's orbit, people in the northern hemisphere and people in the southern hemisphere would have the same seasons. For example, if winter occured because the Earth was far away from the Sun, everyplace on the Earth would be cold at the same time.

But this is not what happens! Summer in the northern hemisphere occurs at the same time as winter in the south, and vice-versa. It turns out that the Earth's orbit is nearly perfectly circular, and the difference between its closest point and its furthest point is very small. In fact, the Earth is furthest away from the Sun in June when it is summer in the northern hemisphere.

The Earth is a very special planet in many ways. Just as Earth's unique atmosphere and its distance from the Sun work together to make Earth the right temperature to support life, Earth's orbit and its rotation work together to create the seasons.

When is the Earth farthest, closest to the Sun?

What Causes the Seasons?



The landscape and weather change greatly during the year in regions that have four distinct seasons. Images Courtesy of Corel
Click on image for full size (161 KB JPEG)
Let's get rid of some common misconceptions about the seasons. The Earth's orbit is in the shape of an ellipse, so that sometimes the Earth is a little bit closer to the Sun than at other times. Is this the cause of the seasons?

You can imagine that if the seasons were caused by the Earth's orbit, people in the northern hemisphere and people in the southern hemisphere would have the same seasons. For example, if winter occured because the Earth was far away from the Sun, everyplace on the Earth would be cold at the same time.

But this is not what happens! Summer in the northern hemisphere occurs at the same time as winter in the south, and vice-versa. It turns out that the Earth's orbit is nearly perfectly circular, and the difference between its closest point and its furthest point is very small. In fact, the Earth is furthest away from the Sun in June when it is summer in the northern hemisphere.

The Earth is a very special planet in many ways. Just as Earth's unique atmosphere and its distance from the Sun work together to make Earth the right temperature to support life, Earth's orbit and its rotation work together to create the seasons.

More on Earth's aphelion and perihelion...


Last modified June 26, 2008 by Vanessa Pearce.
The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. Windows to the Universe® is a registered trademark of UCAR. All Rights Reserved. Site policies and disclaimer