The Naked Sun is a 1957 ScienceFiction and CrimeFiction Novel by Creator/IsaacAsimov, the second of his "Robot Trilogy".

In ''Literature/TheNakedSun'', Elijah "Lije" Baley, freshly promoted from his previous successful case in ''Literature/TheCavesOfSteel'', is contracted by political machinations far above his pay grade to investigate a murder on one of the "Spacer" Worlds -- Solaria, the richest, most sparsely populated, and most technologically advanced of them all. This makes it, of course, the absolute opposite of the overpopulated, crowded, technologically backward Earth of his exclusive experience. On Solaria, humans are thoroughly outnumbered by their robot servants, to the point where every individual person has an estate of hundreds or thousands of ''square miles'', maintained entirely by robot, on which ''they are the only inhabitant'', with the possible exception of a spouse. Even in cases of marriage, Solarians consider it all but inconceivable to come into presence of another human being for any purpose, though Delmarre did so as a matter of "duty". Along with his agoraphobia, this is one of the major barriers to Lije's investigation.

The victim is Rikaine Delmarre, a well-respected but not well-liked native Solarian. The only suspect is his beautiful wife, Gladia, who maintains her innocence despite having been the only person within hundreds of miles at the time of the murder. Lije is assisted for a second time by R. Daneel Olivaw. (The "R" stands for "Robot".) He's fully humanoid, and despite the Solarians' expertise with robots, able to conceal his robotic nature completely. Lije deals with uncooperative authorities, assassination attempts on him and his witnesses, and a world completely different from his own as he attempts to solve the mystery.

!!Tropes include:

* AndroidsAndDetectives: Less emphasis on this than there was in ''Literature/TheCavesOfSteel'', but it's still present.
* BluffingTheMurderer: In the finale, as he lists the motives and means and even opportunities of everyone involved, without focusing on the murderer specifically.
* BrokenRecord: A robot was found at the scene of the murder. It was completely broken down due to the First Law being violated, constantly repeating the victim's last words.
* ConsequenceCombo: Baley is told he will get a possible promotion to class C-7 if he accepts and does a good job, meaning his family will be looked after, he will get better rations, better showers and all that comes with it. However with the offer comes the unspoken threat of declassification if he refuses.
* DamnedByFaintPraise: Everyone Baley meets on Solaria agrees the late Dr. Delmarre was a "good Solarian", which sounds like a decent compliment on the face of it, but it becomes progressively more apparent that it isn't. No one seems very distraught by Delmarre's passing, and their InsistentTerminology makes obvious the fact that no one is willing to call him a good ''person''.
* DeliberateValuesDissonance: Part of the Solarian moral code is that personal contact is obscene. Even standing in the same room as another human induces a little {{Squick}} in most Solarians. Instead, they communicate using 3D holographs that are virtually indistinguishable from the real deal. The disconnect between "seeing" as opposed to "viewing" is extremely wide: viewing someone who is totally nude at the moment is completely acceptable, because hey, it's just ''viewing''. It's not like they're ''actually'' in the room with you. Furthermore, the subject of children and anything to do with them is considered vulgar -- Baley just saying the word "children" is enough to make one Solarian blanch.
* DesignerBabies: All children on Solaria are grown in test tubes and vats, screened for genetic problems, raised collectively and taught to dislike human presence. This is considered a repugnant job, but Delmarre took it out of his strong sense of duty.
* ElectronicSpeechImpediment: Robots who partially violate a Law can suffer damage to their speech programming; one robot who serves poisoned water unknowingly ends up with a lisp. [[spoiler:This is Baley's hint that the completely incoherent robot at the crime scene was something more than a mere witness to murder -- its own ''arm'' was the murder weapon, and when it realized what had happened, the First Law violation caused its programming to snap.]]
* ExactWords: At one point, Baley keeps Daneel held hostage by a group of robots to prevent him from tagging along. Since robots are built on this trope, he is very specific in his instructions not to let Daneel make contact with anyone, since they could countermand Baley's orders to hold him. Fortunately for Baley, he neglects to forbid ''other'' people from contacting ''Daneel'', and this lets Daneel catch up to Baley just in time to save him from an almost certain death by drowning.
* FairplayWhodunnit
* FoundTheKillerLostTheMurderer: [[spoiler:Inverted. Lije catches the murderer but deliberately lets the killer go free.]]
* InnocentFanserviceGirl: Since Solarians despise human contact they communicate with very realistic holograms (called "viewing", as opposed to "seeing"). When Baley first wants to talk with Gladia, she appears naked on the hologram; she doesn't understand his embarrassment, since it's just "viewing" -- it's not as though he's there in ''person'' or anything. Daneel tells her to [[PleasePutSomeClothesOn put some clothes on]].
* IronicName: The Solarians are counted among the ranks of the Spacers. But most of them are barely willing to leave their own homes, much less get on a starship and travel offworld.
* {{It is Pronounced Tro-PAY}}: Gladia's name is pronounced glah-DIE-ah.
* LamarckWasRight: Solarians regard gregariousness as undesirable, and eliminate it through early childhood training. This leads a Solarian paediatrician ("fetologist") to surmise that in a few thousand years, children will be born without the need to socialise.
* MadScientist: Jothan Leebig. [[spoiler:He's the one behind the murder of Delmarre and also the two attempted murders, as he managed to find a way around the First Law, preventing robots from harming humans. Leebig was also planning on using this to develop new robotic military weapons that would have had terrifying consequences.]]
* MakeItLookLikeAnAccident: [[spoiler:All of the attempted murders on Lije and his assistants are carried out through robotic means, despite the laws of robotics! See ThreeLawsCompliant below.]]
* MySensorsIndicateYouWantToTapThat: Daneel can read human body language well enough to suspect that Elijah is falling for Gladia.
* NakedFirstImpression: Elijah's first "meeting" with Gladia.
* NightmareFuel: In-universe examples. Centuries of being cooped up inside walled cities have given all Earthmen intense agoraphobia (fear of the outdoors), to the point that Daneel fears Lije will panic just from seeing out an open window, and flatly refuses to let him open the top of the convertible car they're in when they first arrive on the planet. On the other side of the spectrum, there's Solarians. They've isolated themselves from others for so long that they have anthropophobia (fear of other people). In one case, it's so bad that one of the characters mentally regress nearly to infancy at the thought of being in the same room as another person.
** Jothan Leebig's EvilPlan is this to just about everyone except him. Though it would have been a powerful military weapon, in a society wholly dependent on robots, the thought of circumventing the Three Laws is enough to instantly turn all of Solaria against him.
* OneSteveLimit: Solaria, with its PopulationControl and 20,000 people population, plays this trope literally.
* PerfectPoison: Subverted. The poisoner uses too much poison, and the victim vomits most of it up before it can kill him. He does, however, spend the rest of the book recovering from the dose he ''did'' receive.
* PickedFlowersAreDead: Gladia picks a flower and Elijah remarks that she killed it. Being a murder suspect, she angrily asks whether that's supposed to mean she can kill a human just as easily. [[spoiler: In hindsight, this is rather prophetic.]]
* PleasePutSomeClothesOn: Gladia's first interview.
* TheReliableOne: Dr. Delmarre is something of a deconstruction of this trope. Publicly, he is lauded for his unfailing devotion to civic duty: he volunteered for one of the most important but least desirable jobs on the planet, and never once neglected his marital duties, despite being [[HatesBeingTouched even more anthrophobic]] than most Solarians. Privately, no one really cared for him, as he was also stern and lacking in personality. Not to mention his dutifulness probably fostered the impression that he was HolierThanThou, even if it was only imagined. Nevertheless, he did live a life of willful sacrifice, even if that was the [[DamnedByFaintPraise only good thing people had to say about him]].
* ScienceMarchesOn: Dr. Delmarre and his assistant were still working on how to create children without two people having sex, thousands of years into the future.
** She also complains that there is no way to analyze a person's genes directly, so they resort to analyzing the biochemistry.
* SexIsEvil: Not because Solarians consider it immoral, but because it is the epitome of what they despise most: physical contact. Plus, it is the one form of physical contact they are required to engage in for the sake of their society (except for medical treatment, but that is [[WeWillHavePerfectHealthInTheFuture only occasionally necessary]]). Gladia actually considers herself a sexual deviant simply because, unlike everyone else on her world, physical contact ''doesn't'' repulse her.
* SexIsEvilAndIAmHorny: Gladia, as mentioned above, waged a constant war against her natural desires and her social upbringing, to the detriment of both her and her husband.
* ThreeLawsCompliant: Naturally. There are no mis-programmed robots in this book. [[spoiler:However, there ''is'' an unspoken assumption built into the laws of robotics that becomes highly significant. Law One -- "A robot may not '''knowingly''' injure a human being or, through inaction, '''knowingly''' allow a human being to come to harm." Basically, a robot can perform an innocuous task, individually harmless, which taken along with a number of other tasks performed by other robots or people, would cause a human being serious harm or death.]]
* TitleDrop
* TortureAlwaysWorks: Subverted. [[spoiler: Lije set up events so that the person he pins the murder on will think he's about to be in physical proximity with another human, an idea that revolts him even more than most other Solarians. This causes him to "confess" to his crimes, but he never actually confesses to the murder. Because, it turns out, he wasn't actually the murderer.]]
* YourNormalIsOurTaboo: Though spacers in general are a [[PlanetOfHats society of introverts]], Solaria is unique among the spacer worlds for their Victorian attitudes towards sex and reproduction. To them, it is a necessary evil never spoken of in polite company. Even the word "children" is considered vulgar.