A UNIVERSE OF MYSTERIES: Why aren't there suns, planets and galaxies made of antimatter?
NASA

Our September 2009 special issue on origins contains articles on 57 innovations and insights that shape our world today. They include some big ones, like the origin of life, the universe and the mind; sobering stories, like mad cow disease and HIV; and whimsical tales, like paper clips and cupcakes. This past week, we've posted a dozen additional online-only origins: the open-plan office space, fruit ripening, malaria, the computer mouse, atmospheric oxygen, hatred, wine, dogs, rubber boots, zero and, of course, Scientific American . Lawrence Krauss, a theoretical astrophysicist and popularizer perhaps best known for his book, The Physics of Star Trek, describes his origins symposium held this past spring at Arizona State University. Our origins landing page contains links to some that appear in the magazine.

To end our weeklong look at beginnings, we present eight phenomena whose origins are unknown or lack a definitive narrative of their start. The list is by no means complete, and Scientific American readers are sure to have their own favorite mysteries. Share them with us in Comments

[Slide Show: 8 Phenomena That Defy Explanation]