unexplained phenomena Laser-cut by giants? How did this massive rock in the Saudi Arabian desert get split so cleanly? Mark Frauenfelder

Dizzy The earth's core may have reversed direction. Elías Villoro

History Exclusive interview with Matt LaCroix and Kaedrich Olsen about Gaia's Ancient Civilizations fourth season Devin Nealy

picks NASA: 35 Years On, Voyager's Legacy Continues at Saturn Xeni Jardin

Meet me in Atlantis: my obsessive quest to find the sunken city Mark Adams