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?