In the early 1900s, Robert Goddard proposed sending a rocket to the moon. critics took the position that in a vacuum such as exists between earth and the moon, the gases emitted by the rocket would having nothing to push against to propel the rocket. to settle the debate, Goddard placed a gun in a vacuum and fired a blank cartridge from it. (a blank cartridge fired only the hot gases of the burning gunpowder.) what happened when the gun was fired?