Please contrast How deep underwater do I have to dive to be safe from a 1MT Hydrogen bomb detonation above? with Is outrunning a nuclear mushroom cloud feasible?

Is one really on-topic while the other's off-? It may be that there's an important difference, but I'm not seeing it. If you see it, please explain?

Six months later, with many discussions on scope and topicality having passed by... any new thoughts on whether there really is a difference between the two?

(I've lost my close-vote priveleges to the ratcheting of rep-thresholds, or I'd have just nudged one into a review queue as a way to bump this.)

  • $\begingroup$ This is an interesting question. I'm not sure what's the best answer, hence the comment. But for me the below water one has implications on worldbuilding. You can imagine that a society wants to hide from a nuclear warfare, underwater. And the question to that would be the same as the one we have here. On the other hand, I can't see a society running away on sports cars all the time. $\endgroup$ Commented Feb 12, 2016 at 8:20
  • $\begingroup$ Stack exchange is a democracy, it can be inconsistent. Sometime people like a question and will keep it open despite it being off topic. The opposite is also true: bad questions that are on topic can be closed. $\endgroup$
    – Vincent
    Commented Aug 27, 2016 at 20:33
  • $\begingroup$ @Vincent is it your contention that one or both of those ^^ are at play here? I'm trying to better understand the general sense of topicality around WB. These similar questions obviously live somewhere near the boundary, where some in this democracy say 'aye,' some say 'nay'. What will help me is if people explain reasons for these two questions to be open or closed. (I don't actually care whether the questions live on open or closed or mixed--I'm not of either mind. I ask in hopes of some education.) $\endgroup$
    – nitsua60
    Commented Aug 27, 2016 at 23:11

2 Answers 2


Personally, I think the diving escape from the hydrogen bomb has similar enough attributes to be treated the same way. By the close votes, some others seemed to think so too. The world building potential is about as low as most other what-if questions, and with slight rewording it seems like it might even be well received on Physics.SE.

It's a question that topically fits on XKCD's What-If. There are a lot of these floating around right now, and I think there is substantial hesitation by many in the community to jump into judgement on these questions while we discuss scope (I personally avoided casting a close vote). That may or may not be the right course of action, but there seems to be too much subjectivity over highly-popular questions at the moment. Once the elections are over, I think clarity on these issues will be pursued quickly.

Right now, a lot of questions are not treated fairly. Depending on who is online at any one moment some potentially out-of-scope questions get close votes while others get upvotes. It's a symptom of scope creep and subjective guidelines, which are actively being discussed here.

  • $\begingroup$ I was going to write a reply, but this is basically what I was going to write. :) $\endgroup$
    – Tim B
    Commented Feb 12, 2016 at 9:23

The underwater question is more on-topic than the outrunning question, although both are borderline.

The underwater question is how far down do you have to go so as to survive the nuke. That's a question of setting and how you create the characteristics of your world.

The outrunning question is about a single person's actions and whether they are feasible. The setting is given to us (in particular the distance, which was the previous question). To call this Worldbuilding, we have to basically think of it as a reality check.

Personally, I'm fine with both questions being on-topic. They are both heavily plot-based, but they aren't asking for general suggestions. We are given the plot purely to talk about aspects of the setting. They could both be just this side of the on-/off-topic divide.

The problem with making the underwater question off-topic is that we are essentially being pedantic. Consider the following question:

How far underwater does my city need to be?

In my Earth, there was a nuclear war. Fortunately, some people had moved into underwater cities. I want to locate one near Pearl Harbor, Hawaii. How far underwater does the city need to be to have survived a one megaton hydrogen bomb that hits Pearl Harbor directly? Whatever the depth, I want it to be as close to Pear Harbor as possible. So if you tell me one kilometer, then I want to locate it at the closest one kilometer deep water to Pearl Harbor.

This question seems clearly on-topic to me. It's about aspects of the world rather than the plot. But it's essentially the same question and will have very similar answers. So if we make the other question off-topic but accept this one, we are essentially encouraging people to lie about what their real question is so as to comply with an arbitrary rule boundary.

You can sort of do the same with the outrunning question, but it's more complicated and may require multiple questions. Rather than having one person trying to escape in one car, ask about traveling into the blast crater. When ten kilometers from the center, how does the road look? Are there cars on it? How close to you have to get before fleeing cars couldn't escape? What do they look like? Are the tires still there?

So in my opinion, both questions should be on-topic, although we should guide people to concentrating more on setting and less on plot. I do think that the underwater question is slightly more on-topic than the outrunning question.


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