This story was first published in The Magazine Of Fantasy And Science Fiction (July 1956 issue), by Isaac Asimov, and reprinted in the Japanese February 1960 issue. As a Science Fiction and Mystery Fiction Genre Mashup, this Novelette is the third story featuring Dr Wendell Urth, scientific detective.
After ten years, the three friends who earned their Astronomy doctorates at the same time are having a reunion. Each one talks about what they've been accomplishing since graduation day, and how difficult it is to readjust to visiting Earth.
Edward Talliaferro has been living on The Moon, where a Lunar base has been established whose astronomical focus is on the atmospheres of Earth and the inner planets. The gravity is 16% of Earth-normal, and going outside of a building without a spacesuit is oddly uncomfortable. Even the daylight is odd, since it lasts for twelve hours instead of fourteen days.
Stanley Kaunas has been living on Mercury, where the Observatory has been perched at the northern rotational pole. From there, half of the Space Base is always in darkness and the other half, with the telescope, is pointing at the sun, where they can analyze sunspots and solar flares in the minutest detail. The sunlight there is more lethal than anywhere else, even with a spacesuit on, and gravity is 40% of Earth-normal.
Battersley Ryger spent the past ten years living on Ceres, where the telescopes are aimed at everything outside of the asteroid belt. The pseudo-grav fields adjust conditions to 80% of Earth-normal gravity, but the asteroid rotates in only two hours. Dr Ryger is the one to point out the difficulty of remembering that you don't need a spacesuit to leave a building on Earth.
A sour note hangs over this reunion, driving the expected joy into a somber meeting. There was supposed to be four of them, but their friend, Romero Villiers, had fallen sick at the end of their doctoral studies, and has been confined to Earth because of his illness ever since. He arrives and proclaims to them that he has solved the problem of mass-transference, which will eventually allow him to visit each of their Observatories without needing to endure the lethal acceleration that rocket-based spaceflight requires. He leaves, appearing furtive and obsessed, claiming that the classmates who abandoned him won't be able to steal his research paper before he gives an incredibly public speech the day after tomorrow. He dies only a few hours later, and all three are implicated in his death.
"The Dying Night" was republished several times; Fiction (issue #43, June 1957), Nine Tomorrows (1959), Galassia (issue #27, March 1963), Asimovs Mysteries (1968), The Best Of Isaac Asimov (1973), and The Complete Stories, Volume 1 (1990).
"The Dying Night" contains examples of:
- Artificial Gravity: A technology called "grav-plating" is used to make the gravity inside the base on asteroid belt object (dwarf planet) Ceres equal to 80% of Earth-normal.
- Colonized Solar System: Each of the three suspects for this case has been living for the past ten years in an interpanetary base; Mercury, The Moon, and Ceres (in the asteroid belt).
- Conviction by Contradiction: Wendall Urth, Phone-In Detective, deduces the killer's identity through the circumstantial evidence of "he was the one most surprised by sunlight". The flaw in this reasoning is that both Mercury and The Moon have very long nights. The assumption that the light-sensitive recording would be safe in starlight (and safely retrieved days later) could have been made by either of Dr Kaunas or Dr Talliaferro. The justification for proving which one of them killed Romero Villiers is now Conviction by Counterfactual Clue due to an astronomical assumption being proved wrong (we now know that Mercury rotates around the sun twice for every three "days").
- Conviction by Counterfactual Clue: Wendall Urth, Phone-In Detective, deduces the killer's identity through the now-incorrect evidence that Mercury is a Tidally Locked Planet. The killer had assumed they could safely store a light-sensitive recording in starlight and retrieve it days, or even years, later without the recording being exposed to sunlight. Current astronomical understanding is that Mercury has about three days for every two years it experiences.
- Defective Detective: Dr Wendall Urth is an extreme claustrophile, and hates travel. He only travels on foot; forgoing cars, boats, and planes. His mildly obsessive behaviour often puts off his guests, but his deductive abilities are superb. The cases he's given are always of a Science Fiction type.
- The Exotic Detective: Dr Wendell Urth, an extremely agoraphobic detective who solved cases brought to his attention without ever leaving his home. For added exoticness, the crimes themselves often occurred in space!
- Mad Scientist: Romero Villiers would have been one of the greatest astronomers of his generation, but his illness prevented him from going into space where the newest tools were available. His three classmates, however, went without him, and over the next ten years, he grew more and more paranoid and resentful of them.
- Mind Probe: Dr Asimov's Psychic Probe is a technology that can extract information from people's unconscious memories. It's used as a threat because people who are subjected to the Probe often suffer permanent damage. The detective who fingers the culprit points out that this damage is due to mishandling or from resisting it.
- No Plans, No Prototype, No Backup: (Zig-Zagging Trope) Romero Villiers has invented a mass-transference device. His prototype worked long enough to transport a mouse, demonstrating its effectiveness, but breaks down afterwards. He's been excessively secretive, believing that someone will try to steal his notes, so he only has one copy of the research paper (everything else is kept in his memory). When he dies of a heart attack, his murderer photographs the paper and burns the original. The negatives are hidden in a safe place, until sunlight overexposes the film. Now there's nobody alive who can design the device. The investigator, however, explains that the unconscious memories of the murderer can be recovered under a Psychic Probe.
- Phone-In Detective: Dr Wendell Urth is so afraid of travelling that police and other people always bring the cases and evidence to him, rather than bringing him to the scene. He usually solves everything merely from the information given.
- Teleportation: Romero Villiers invents a device able to perform mass-transference, another way to say teleporation. It requires a base station at each end, but will be used to create Casual Interplanetary Travel.
- Tidally Locked Planet: Mercury is tidally locked to the Sun, and this becomes a major plot point. The killer had lived on Mercury's northern pole for ten years, forgetting the normal night/day cycle of Earth. After astronomers found out Mercury wasn't tidally locked, Dr Asimov said in an author's note that he'd wanted to fix it, but couldn't figure out how to do it without rewriting half the plot.