The countdown has begun toward humanity’s first launch to the moon in 53 years. NASA’s countdown clocks started ticking late Monday afternoon at Florida’s Kennedy Space Center. The 32-story Space Launch System rocket is poised to blast off Wednesday evening with four astronauts. After a day in orbit around Earth, their Orion capsule will propel them to the moon and back. NASA says the rocket is doing well after the latest round of repairs. The last time NASA sent astronauts to the moon was during Apollo 17 in 1972.