Authentic Science Fiction Monthly No. 50 — page 103: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

AUTHENTIC SCIENCE FICTION soluble, but the little that goes into solution so affects the surface tension that movement of water molecules takes place rapidly and the craft is seen to move steadily for a long period of time. Now, when we come to consider the movement of almost all objects on Earth, in order that one thing shall be moved in a given direction something else is moved in the opposite direction. When a shell is fired from a gun, as the shell moves forward the gun moves backward. The shell, of course, is much lighter than the gun and so the shell moves forward much more quickly, and farther, than the gun moves backward. Newton’s statement that the reaction, besides being op- posite to the action, is equal to it, enables us to calculate the speed of recoil of a gun, the weight of the shell and the muzzle velocity of the shell. When ‘Newton said that the reaction is equal to the action he meant that the force which pushes the gun backward is 102 equal to that which pushes the shell forward. The shell ‘is lighter than the gun and, therefore, the forces due to firing of the propellant pow- ders in the cartridges cause the shell to move rapidly and the gun to move less rapidly. On Earth we can walk or run and jump by pushing the Earth away from us. We do actually move the Earth when we jump into the air, but consider the number of times the Earth is heavier than a man and divide the height he jumps by this number to see how small a fraction of an inch the Earth moves. And, of course, when the man falls back to Earth, the Earth also falls towards the man through the same small distance and all is as it was. On water we can move a boat with oars or paddles which push water backwards away from the boat so that the boat moves in a forward direction. When the internal com- bustion engine gave us suffi- cient power to turn a propeller comicloolks.com