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)
Thursday, January 10, 2013
Today's Astronomy Picture of the Day depicts "cosmic bullets" in the Orion Nebula. What are these? The text talks about shock-heated hydrogen gas, a natural process.