Tomorrow will be the fiftieth anniversary of the first time a human orbited the earth, when Soviet cosmonaut Yuri Gagarin rocketed into space, made almost a complete circuit around the planet, entered the atmosphere, and returned to terra firma. By international standards in place at the time, his flight didn’t meet the technical requirements for human spaceflight, which demanded that he return to the planet with his spacecraft (he ejected and parachuted down separately), but no one knew this at the time, and it was another great propaganda victory for the Soviets in the space race with the Americans, who were still reeling from the Sputnik surprise three and a half years earlier.

It’s another human spaceflight anniversary as well. It will have been exactly thirty years since the first flight of a Space Shuttle (Columbia), on April 12th, 1981. The program is scheduled to be retired this year after three decades of service (including two periods of almost three years each when it was shut down as a result of the Challenger and Columbia losses, in 1986 and 2003, respectively). That the date is the same is a coincidence — NASA had originally scheduled the first flight for April 10th, but a computer timing glitch delayed it for two days, serendipitously resulting in the inaugural launch occurring exactly two decades after the first human spaceflight.