"The moon is airless, waterless and lifeless, days and nights are two weeks long, temperatures range from that of boiling water at noon down perhaps to that of liquid air at midnight. The men of the ship would walk on the moon clad in diving suits. Gravity being only one-sixth that of the earth, a man would carry several hundred pounds of apparatus for providing air and for regulating the temperature. "To leave the moon the ship would fire her rear cannon and coast back to earth. By firing its forward cannon it would cushion its landing on the earth, which would have to be made on a desert, because of the tremendous charges the cannon would fire." _A Meeting Place for Readers of_ Astounding Stories [Illustration: The Readers' Corner] _The Author Explains_ Dear Editor: Am very much puzzled by the several apparent mistakes in two of the stories in the April issue of Astounding Stories. In "The World Behind the Moon," Mr. Ernst makes an error so obvious that it almost makes me believe that it isn't an error. Like doing a math problem and finding it so easy that you're sure that you have it wrong. Anyway, here is my problem; this is taken verbatim from the story: "At two thousand miles from the Earth there had still been enough hydrogen traces in the ether to give purchase to the explosions of their water-motor." Does the author mean to say that the explosions of the tubes have to have something to push against to have any action? (a) Has it not been proven actually and mathematically that the explosions of rockets and expanding gases are even more powerful in space? The space ship in this story was equipped with both bow and stern tubes; why not fire them to slow the ship down instead of waiting to run into some resistance? (b) Also, when they landed they took some air-guns which shot bullets containing a liquid which exploded when heated by the passage of the shell through the barrel; then the author goes ahead and tells us that the planet was about as hot as the tropics. Such heat should explode the bullets, but it didn't. Why? Mr. Ernst has his heroes do a lot of running around on that little planet. (c) Since the planet is smaller than the moon, it hasn't much gravity and therefore can't retain a very heavy atmosphere, or one very thick. Anyone doing all that violent exercise would probably die of exhaustion before many minutes of it.