How Do The Seasons Work?

Relatively Interesting September 2, 2010 4
How Do The Seasons Work?

What makes the seasons change and how do they work?  With September upon us, the days are getting noticeably shorter, the nights cooler, and winter is only three short months away.

A common misconception is that we are closest to the Sun in the summer… but this is actually the opposite.  The Earth is at it’s farthest from the Sun on the first day of summer.  So why is it warmer in the summer then?

The elliptical orbit of the Earth around the Sun 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 our seasons. This tilt, combined with the Earth’s rotation around the Sun, produces two effects:

1)  A variation in the amount of daylight each hemisphere receives
2)  Seasonal weather (colder in winter, warmer in summer)

Variation in the Amount of Daylight:

By looking at how sunlight is landing on the planet in the diagram below, you will notice two things:

  • In the winter, the Southern Hemisphere is getting more sunlight than the Northern Hemisphere.
  • In the winter, the North Pole is getting zero sunlight, which is why it experiences 24 hours of darkness in January.

season

Image Credit:  Roy Flookes and Dave Donkin


If the Earth was at right angles to the Sun, day and night would always be equal length, and there
would only be one season throughout the whole year. 

Seasonal Weather:

sunlight concentrationThat huge difference in the amount of sunlight reaching the ground in the different hemispheres also causes the seasonal weather. Note that in the winter, the same amount of sunlight is being delivered by the sun, but it is spread out across a much greater surface, thus having less of a warming effect. The diagram below illustrates this effect.

NASA provides an animation which shows the changing seasons and the effect of seasonal temperatures on the entire Earth:

http://earthobservatory.nasa.gov/Features/BlueMarble/BlueMarble_monthlies.php

For additional information, Riverside Scientific Inc. has produced an interactive application which allows students to easily visualize how the seasons work and why they change.  The application, RSI Seasons, is available as a trial on their website.

4 Comments »

  1. Mark Robinson May 9, 2011 at 3:59 am - Reply

    Your explanation is fine and all except that it is extremely northern hemisphere-centric (a geometric oxymoron, I know). When you write "… we are closest to the Sun in the summer…" I'm guessing that you're just talking about North America since Europeans tend to be less insular. As I'm sure you're aware, the earth *is* closer to the sun in the southern summer.

    Perhaps you could amend the text to reflect a global-perspective since you are talking about an entire planet and it's relation with respect to the sun.

  2. Anonymous October 13, 2011 at 4:37 am - Reply

    Thanks this really helped!!!!!! :)

  3. Anonymous December 13, 2011 at 1:08 pm - Reply

    Thanks this did help I'm doing a project in school so I need all the help I can get Thanks!:)

  4. xBelieveInEve January 5, 2012 at 1:44 pm - Reply

    hi my name is eve it is really hard to do science for me cause i think im stupid lol xD i wish there was more to seasons though like i know all about seasons since i was in like kindergarten :/ but it is always the same thing. I'm not saying this article is bad actually it's really REALLY great. i just want to know a website as great as yours to learn more about i have researched about seasons for 3 MONTHS! and its all the same thing any help? link? anything? that what be epic! btw the girl above me is my bestie :]love you gurrrrrrrrrrrrrrrl <3 143 <4 haha xD

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