Wednesday, December 21, 2011

The Winter Solstice and a Catalog of Astronomy Apps


Happy winter solstice everyone -- the shortest day of the year -- officially at 9:30 pm PST, on Dec. 21, 2011.  It's the beginning of winter in the Northern Hemisphere of the Earth. Because our planet is tilted (leaning to one side), the two hemispheres get different amounts and intensities of sunlight as the year goes on, and thus we have seasons. In the summer, we have long days and shorter nights, while in the winter we have long nights and shorter days. All this happens because early in its history, some cosmic accident knocked the Earth over a bit and -- like many accident victims -- it had no way of straightening out. Venus and Jupiter orbit the Sun with their axes pointed straight up, and don't have seasons like we do.
 
Many of our winter holiday traditions have their roots in ancient celebrations of the winter solstice.  To make sure the Sun-god increased his presence in the coming months (and to cheer everyone up when the days were short), many ancient people had festivals with music and song, sacrificed a food animal, and gathered around a fire with loved ones. So, if you are enjoying the winter holidays right now (and I hope you are), give a little thought of thanks to whatever mini-planet or planets knocked our Earth over a bit at the time our solar system was first forming.
 
As a little solstice present, I thought some of you might like to see a new article I published today, which is a listing of 98 astronomy apps you can get free or buy for your smartphone or tablet:
http://aer.aas.org/resource/1/aerscz/v10/i1.../p010302_s1

As some of you know, my hobby is making resource guides. Some people knit or shoot hoops when they need to relax; I make bibliographies and catalogs. With the help of a student volunteer, I scoured the web to find apps that can help you enjoy many aspects of astronomy. The listing includes a variety of apps for displaying and explaining the sky above you (some using the GPS function in your device); a series of astronomical clocks, calculators, and calendars; sky catalogs and observing planners; planet atlases and globes; citizens science tools and image displays; a directory of astronomy clubs in the U.S.; and even a graphic simulator for making galaxies collide. Enjoy....

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