Explaining Earth’s Four Seasons

Learn why Earth has four seasons and what its position in space has to do with it.


| January 2018


Mother Earth News Almanac: A Guide Through the Seasons (Voyageur Press, 2016), by the MOTHER EARTH NEWS staff is a collection of helpful information and advice to living a self-sufficient lifestyle. The book provides fun and practical ideas on topics such as raising animals, canning, making compost, and more! The following excerpt is from Chapter 1, "The Planet Earth."

You can buy this book from the MOTHER EARTH NEWS STORE: Mother Earth News Almanac

The "black void of space" — as we sometimes say — is neither as black nor as empty as popular folklore would indicate. It now seems fairly certain that the detectable universe contains at least one trillion galaxies, each of which is made up of billions of stars. Around each star, in turn, may revolve several planets, many of which have satellites of their own.

It is estimated that a single galaxy, the Milky Way, contains a minimum of 100 billion stars. On the edge of that cluster, nearly 27,000 light years from its center, is our own sun...circled by nine known planets.

One of those planets (we call it Earth) revolves — at a distance ranging from about 91,500,000 to 94,500,000 miles — once around the sun every 365 days, 6 hours, and 53 seconds. At the same time, the earth rotates on its own axis (which is tipped at an angle of almost 23-1/2 degrees to the plane of orbit) once each 23 hours, 56 minutes, and 4.09 seconds.

We call every one of the earth's complete circuits of the sun a year — and, if the globe on which we live "sat up straight" (instead of being canted over about 23-1/2 degrees the way it is), every day of every year would be almost exactly the same at any given spot on the planet's surface. As it is, however, that seemingly insignificant little tilt is the major reason that the earth's Northern and Southern Hemispheres enjoy opposing summer-winter and spring-fall seasons.





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