It's been a long time since I read the Larry Niven story "Neutron Star," so I'm relying mainly on the Wikipedia article (linked). The body of my question is hidden behind spoiler tags because there's basically no possible way to ask the question without betraying an important point that is supposed to be dramatically revealed in the course of the story.

The premise of the story is that the protagonist goes on a mission at the behest of the puppeteers to find out what happened to a previous flyby mission to a neutron star. The danger turns out to be that there are strong tidal forces when you get close to the thing. Nobody anticipates this danger: not the puppeteers, not the people on the previous mission, and not the protagonist. At the end, it's claimed that the puppeteers didn't anticipate the existence of tidal forces because their homeworld has no moon. On the face of it, the whole premise just seems silly. This is basic freshman physics. Is there some other factor that makes the premise more plausible? There are a couple of notes in the WP article that seem to discuss this, but they're tagged "citation needed" and "dubious - discuss," and they don't make much sense to me. They seem to claim that the puppeteers do know about tidal forces. But in that case, why would they keep sending human proxies on suicide missions?

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    No, I don't think there's a plausible in-universe explanation. Niven was simply doing what a lot of science fiction writers did in that decade: take a scientific phenomenon that most readers wouldn't know about, and have the characters run smack into it. – Beta Apr 15 '15 at 0:31
  • The same basic idea got used again in "There Is A Tide", where it's just as ridiculous. – Mark Bessey Apr 15 '15 at 2:55
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    This seems to be a rant rather than a genuine question. Can you explain what you're asking a little better other than "This is dumb, ammiright?" – Valorum Apr 15 '15 at 5:37
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    @Richard I disagree. The OP is clearly asking if there's some scientific explanation he's missing. – Mr Lister Apr 15 '15 at 19:01
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    @Richard Ehm, he's probably asking about an in-universe scientific explanation. – Mr Lister Apr 15 '15 at 19:04

The puppeteers know about tides - we learn that in "Ghost" , the framing story for the "Crashlander" collection when Ander Smittarasheed tells Shaeffer.

It's just that they are rather pleased that Shaeffer comes to a wrong conclusion about their home planet, because from there paranoid point of view having humans misinformed beats humans being not informed at all (because uninformed people might look anywhere, misinformed people will look only for planets without moons). And frankly, Shaeffer is not exactly a genius, so this was just him being dumb in the first place.

As for "why did the puppeteers send humans", Shaeffer offers the theory that the original research team flew to the neutron star without telling the puppeteers (who were aware of the dangers and could have warned them), but that after the fact the puppeteers felt that is was prudent to let the humans figure out themselves what went wrong while feigning ignorance (instead of offering an apology or something like that).

Out of universe this is obviously retconned after Niven realized that (by todays standards) the story doesn't hold up. He even has Shaeffer going "I must have been crazy to believe a spacefaring species doesn't know about tides" (not the actual quote, I have only a german translation).


I think the confusion comes in part from the way we do space travel today. Missions are developed and implemented by large engineering and operations teams, with most every contingency planned for. The way we do space travel, extreme tidal forces would have been anticipated and planned for. But by the time Beowulf Shaeffer is alive, space travel is like aviation today. The people who travel in space are civilians of all kinds and the people who fly the ships are trained pilots, not physicists or scientists of any stripe. A few pilots might know about the dangers of neutron stars, but most would simply know to stay well away from deep gravity wells and not care why. I'd expect the average human citizen in Known Space to have no clue at all. And why should they? The world they live in is safe, heavily regulated and cossetted by high technology. In "Grendel" Beowulf Shaeffer walked away from a Mach 8+ aircar collision. And that was without being inside a General Products hull, an all but magical technology that lulled many into a false sense of security.

Puppeteers, except for a tiny handful out of the trillions alive, don't fly in space at all. Nessus, the Puppeteer in charge of the scouting mission, is a canny spymaster and social climber but no physicist. The Puppeteer civilization may well know about the dangers of neutron stars, but Nessus as an individual might not. High acceleration in free fall orbits is generally safe, and a routine space traveler will be accustomed to that; the high gravity gradient near a neutron star introduces a new dynamic that could easily be overlooked.

The point of the neutron star expedition was to take scientific measurements that would ultimately be used by Achilles to figure out how to create neutronium without needing a supernova to compact it. Achilles then scattered stasis-field stabilized miniballs of neutronium behind the escape route of the Puppeteer worlds to lure and destroy any unwary followers. Achilles no doubt knew of the tidal forces but was indifferent to the deaths of humans. Puppeteers used humans as scouts and explorers because humans would take risks even an insane Puppeteer would not.

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