These great hollow globes of artificial super-metals, and artificial transparent adamant, ranged in size from the earliest and smallest structures, which were no bigger than a very small asteroid, to spheres considerably larger than the Earth. (Olaf Stapledon, STAR MAKER)
Wednesday, April 6, 2016
Today's Astronomy Picture of the Day is a very graphic illustration why crewed exploration of Jupiter space will be so difficult. A lot of shielding is going to be needed to keep that crew alive!