Story, first published: Astounding Science Fiction, Nov. 1940
In "Sunspot Purge" ... human progress is downward and all efforts seem to make no difference. The world is going nuts - suicides, murders, a wave of violence are sweeping the world. Two newspaper reporters travel five hundred years into the future and find a dead city. In old newspaper files, they read a story of declining business, increasing unemployment, a fatal economic depression, a complete slide down the scale into barbarism. The irony of it all is that sunspots, or the lack of sunspots, are the cause.
The reporters go forward, hoping that humanity will make a comeback, but after two thousand years, they find nothing. The city is gone. A heap of earthy mounds remains where mutated animals shuffle and slink, and trees and grasses have taken over.
Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.33