JF Ptak Science Books Post 1113
Earlier in this blog I wrote about odd, extraterrestrial extra Earths--double Earths (like this, for example "Extra-Earth Humano-Alien Souls from Outer Space Repopulate Earth-Hell!")--and then branched out to other strange things found in created skies. This image would certainly classify: its the cover art by the fabulous Frank R. Paul for Stanley D. Bell's "Martian Guns" found in the January 1932 issue of Wonder Stories. There's really no way to determine how big the gun is except to say that it is probably "big"--there's just nothing to place the thing in perspective, as the figures in the foreground, being Martian, don't have a specific height. They could be 6' tall, or 60'--perhaps they're only 1/10 of an inch tale, and the projectile they're firing to the earth is so devastatingly powerful that size doesn't matter.
We also have no idea of the used to get the projectile/bomb moving--the nature of the explosive--but it is probable that the resulting muzzle flash wouldn't look anything like what we're seeing here. This depends on the available bits in the microgravity, but I think all that you'd see as a result of firing canon would be a very bright flash of light, and here would be no smoke. Plus lots of other obvious stuff, like, well, the Martians, though at least the gun isn't pointed directly at the Earth, which I think is just a function of fast work. But no matter, this was 1932, and the specs don't matter, as this is, after all, science affliction.
The destructive units are finding their targets, though; one seems to have found its mark around San Francisco, and another looks like it might be in France. They're easy to spot, made so for the reader, finding their thousand-mile high smoke plume in a cloudless atmosphere and all.
I'm sure it would've been an unsettling experience to the reader of the time.
Here's another odd bit, this one seeming to show an exploding Earth--the "exploding Earth" subcategory of the "Strange Things in the Sky" category being among the rarest of these sorts of images. This comes from the January 1932 issue of Science Wonder Stories, from the "Before the Asteroids" article by mechanical engineer Harl Vincent (1893-1968).
I can't find the text of the story, so I really don't know if this is the Earth being detonated or whether it is an asteroid--I prefer it to be the Earth, and the exploding thing doesn't look much at all like an asteroid.