Expert: Ed - 4/14/2004

Question
HI

Right now the earth axis is tilted, but if it was not tilted then what would happen? I know that due to eccentricity there would be a cold period and a warm period because earth will be cloaser to the sun at a point in time. But overall what would happen? I beleive that there would be only one type of season (maybe a mild winter, or hot summers). I just wanted to to ask you.

Thanks
arpan

Answer
Arpan,

Yes, you're on the right track.  In the middle latitudes, (what are called the "temperate zones" in the real world), we have seasons because of the Earth's tilted axis.  If the Earth's axis were not tilted, we would have no seasons.  The day and night would always be approximately the same length of time, like at the times of the equinoxes in the real world.

I think it's also safe to assume that the equatorial regions would get even hotter than they are now, and the arctic and antarctic areas would be colder.  At every point on the Earth's surface, the sun would rise every morning at exactly the same spot, and every evening it would set at exactly the same spot.

For a really interesting, fun book that helps me to think about this kind of thing, I would like to recommend that you read "Mission of Gravity," by Hal Clement.  It's about a planet which rotates so fast that centripetal force results in some balancing out of gravity, in the tropical regions.  It is so interesting, it makes it easier to think about things like axial tilt, seasons, etc.  Hal Clement's real name was Harry Stubbs, and he taught science at my high school.  He died this past Halloween, so I'm trying to pass along his memory to people.  He was a cool guy, and an awesome writer.  I hope you read the book!

Have a good one, and always remember -- Keep Looking Up!
--Ed