Last of the novelettes up for a Hugo is Brad Torgersen’s “Ray of Light,” from Analog. Only a partial extract is free online, but you can buy it for a song (or almost) on Barnes and Noble here, or on Amazon here.
On the ocean floor, a few thousand people, perhaps the last remnants of humanity, live in Deepwater stations situated near thermal vents. Torgersen imagines a frightening catastrophe: an alien ship arrives and stations itself near Earth. No space battle ensues: it ignores attempts to communicate and soon leaves. But the light from the sun begins to dim, and it is discovered that the aliens have placed an enormous cloud of mirror-like objects in orbit around the sun, just inside Earth’s orbit. The objects are absorbing or blocking the sun’s light, and eventually the cloud grows so large that Earth is in complete darkness. Without light, the temperature plummets and Earth begins to freeze over.
At the opening of the story, how it happened is history; the people living in the hastily constructed ocean-floor stations have been there now for over 20 years. And their children, who have never seen the sun, are getting secretive and rebellious.
[In all the previous stories I’ve discussed, I’ve gone on the assumption that everyone has read the story before coming here. I hope that’s the case now, and if you haven’t read it, you definitely should not continue. Suspense is important to the experience of “Ray of Light” and it would be a pity to go into the story already knowing the end.]
Max Leighton, who before the catastrophe was an astronaut, now lives in one of the undersea bases. His only family member is his 15-year-old daughter, Jenna; his wife committed suicide about a decade earlier, depressed and unable to cope with the sunless life. Now Leighton discovers that his daughter, and a number of other teens, have disappeared from the base, taking some of the small submarines that are used to travel between the Deepwater bases. He has to figure out why and where they’ve gone, and the progress from the black depths of the sea to the ocean surface, bathed in the brilliant light of the sun, is convincing and emotional. The cloud has passed beyond Earth’s orbit; the sun is shining again and the ice is melting.
This is a classic what-if SF scenario, and a great experience.