Puzzler 1 (2, 3, 4) The Earth spins on its axis once every 24 hours, making our day 24 hours long. How long is a moon day? Explore the Moon | Lunar Puzzlers | Last Man on the Moon Hear the Space Pioneers | Origins | Resources Transcript | Site Map | To the Moon Home E-mail | TV Schedule | Web Schedule | Teachers Previous Sites | Search | Site Map | Shop | Printable page PBS Online | NOVA Online | WGBH ©