Space exploration is one of the things I get passionate about.
The pic is usually entitled "Earthrise". It was taken in 1968 by astronaut Bill Anders, during the Apollo 8 mission. Apollo 8 was the first manned mission to orbit the moon. I have a 22" by 16" laserprint reproduction of that photo, purchased from the Kennedy Spaceflight Center's souvenir shop, hanging on our living room wall. :)
I should have made clear that I only posted the last two stanzas of that poem. The full poem appears in Heinlein's story "The Green Hills of Earth"; in the story it's attributed to the blind minstrel Rhysling, a spaceman until an accident blinded him.