Human hibernation may not yet be a reality, but that hasn't stopped people from trying. Future-thinking entertainer Lady Gaga is carried in an egg-shaped vessel at the Grammy Awards in Los Angeles on Feb. 13. Ms. Gaga claimed that she incubated for 72 hours before her performance. Danny Moloshok/Reuters
Sam Worthington's character Jake Sully sits in front of his alien double, seen floating in suspended animation, in the movie 'Avatar' (2009). 20th Century Fox/Newscom/File
A model demonstrates an oxygen capsule at the Tokyo Health Industry Show in 2008. The capsule was designed to improve health and skin care by supplying hyperbaric oxygen. Kim Kyung-Hoon/Reuters/File
Sigourney Weaver plays Ellen Ripley in a scene from 'Aliens' (1986). 20th Century Fox/Newscom/File
Athena Dogias takes a nap in a sleep pod in a central business district office building in Sydney in 2006. Busy workers are invited to put their feet up for 20 minutes to rejuvenate and relax in style while listening to music in the dome-shaped pod. Mark Baker/AP/File
The character Austin Powers was suspended in time in this capsule, a prop from the 1997 movie by the same name. Giulio Marcocchi/Sipa Press/Newscom/File
Serge Therrien relaxes in a sensory deprivation tank called a 'floatarium' at the Tranquility Float Centre in Toronto in 2003. Tannis Toohey/Toronto Star/ZUMA Press/Newscom/File
At Comic-Con 2010, fans celebrate the release of 20th Century Fox Home Entertainment's Alien Anthology Blu-ray by boarding the Nostromo and entering the hibernation chamber for a first-hand Alien experience in San Diego. Casey Rodgers/AP Images for Twentieth Century Fox Home Entertainment/File
Alcor Life Extension Foundation public relations manager Paula Lemler looks over storage units which contain liquid hydrogen frozen heads and bodies at the cryogenics lab in Scottsdale, Ariz., in July 30, 2003. The room contains 58 people. Tom HoodAP/File
Han Solo is frozen in carbonite in Star Wars Episode V: The Empire Strikes Back (1980).
Model Haruka Shioji relaxes in an egg-shaped capsule designed to clean your body and spirit at a Tokyo aesthetic salon in 1999. Toru Takahashi/AP/File
Estimates of the number of disappeared people in Mexico during a decade of drug and gang violence rival numbers from Argentina's Dirty War and Colombia's armed conflict. New laws protecting victim's rights require the government to establish a national registry of those who have disappeared.
ByEmily Pickrell, Contributor
One of the startling unknowns in the story of Mexico’s recent wave of violence is just how many people can be counted among its disappeared.