Thursday, September 21, 2006

Seasons Change

I was all set to write a "Yay! Happy first day of autumn!" post today, but I thought it would be a good idea to double-check that it actually is the atumnal equinox today before posting erroneous information. It's a good thing I checked, since it is technically still summer until Saturday. For some reason, I had it in my head that the solstices and equinoxes were almost always on the 21st of the month (March, June, September, December), but that is not the case.

  • The vernal equinox falls on March 21st every 4 years and on March 20th the rest of the time.
  • The summer solstice is always on June 21st. (Well, it has been for the last quarter century. Back in the 60s it fell on the 22nd.)
  • In 1996, the atumnal equinox shifted from being on September 22nd every fourth year and September 23rd the rest of the time to switching off every two years. This year it falls on the 23rd.
  • The winter solstice alternates between December 21st and 22nd every two years.

The linked pages have little tables and diagrams showing the changes each year. I wouldn't want to be the one sitting around and figuring all that stuff out (so thanks, astronomers!) but it's kind of neat to look at.

All right, enough procrastination via blog. Back to work on my Powerpoint presentation. More from me in a couple of days.

No comments: