Skylab 4 commander Gerald Carr jokingly demonstrates weight training in zero gravity as he balances fellow astronaut William Pogue, the mission's pilot, upside down on his finger.
Skylab was America's first space station and orbital science and engineering laboratory. The station was launched into Earth orbit by a Saturn V rocket on May 14, 1973, as a follow up to the Apollo program. Three crews visited the station, with their missions lasting 28, 59 and 84 days, respectively.
Image Credit: NASA