There are three recent questions that are asking about how things would be different on a fictional "alternate earth" with different parameters:

It's previously been established that geoscience questions related to other (real) planets are on topic, but that's a little different to "if earth were different in parameters A and B, how would things X and Y be different".

We've previously discussed "movie science" questions, although I'm not sure whether consensus was reached, but these questions are different - they're reasonable geoscience questions (albeit mostly too broad at the moment) that happen to relate to a fictitious, hypothetical scenario. They would certainly be on topic at Worldbuilding, but that doesn't mean that they don't also belong here.

Should these questions be on-topic at Earth Science? If so, how should they be signposted to make it clear that they do not refer to reality? (a tag? A prefix to the title?)


4 Answers 4


Yes, as long as such planets are physically feasible or otherwise give insight into real physical processes.

Serious earth and planetary scientists are involved in this kind of work, in particular in the context of modelling the climate on extrasolar planets. For example:

And in any kind of models, including climate models, it is common practice to run the model with some toy simplified world. For example, one might run two climate models with a planetary configuration consisting of a world with the surface covered entirely by an ocean. Much simpler to keep out those pesky continents.

Of course, within those toy worlds, questions should still be focussed. A question like what would the climate look like? might take 5 TB of data to answer. Not good.


Personally, I think these mental exercises are useful but really complex. Unless I feel it helps me understand a specific Earth Science process or problem, I am going to likely request for a migration to Worldbuilding and see what the community decides.


I am against allowing questions with hypothetical situations here with the exception of (reasonably scoped) questions referring to situations that could easily happen on Earth in the foreseeable future.

Here are my reasons why I disagree:

  1. It would create a rather big overlap with World Building SE. Overlap between sites is inevitable, but I feel that we should try to limit this if possible. At the very least we should not actively widen the scope of an existing SE site if there already is another SE site for exactly those types of questions.

  2. Several of the 'world-building' questions that were posted here were rejected from the world-building site because they were too broad. If we allow such questions we run the risk of becoming the default 'dump' site of rejected WB questions.


Through science or God, man will prevail. To question whether to host "fictional or hypothetical theories" is equal to censorship. Promoting freedom of thought should be paramount.

It took but one question to start this journey, no matter your education you still ask the same question.

Plz allow the mouth of babes to do the same.


  • $\begingroup$ Er... That's nice? So, do you feel that we should host questions about hypothetical or fictional planets? 😊 $\endgroup$ Jan 14, 2016 at 8:36
  • $\begingroup$ In fact any question. Imagine if Galileo didn't suffer censorship. $\endgroup$
    – charmy
    Jan 14, 2016 at 8:59
  • $\begingroup$ ah, so your argument is that anybody should able to ask anything they like on the site? I think that's a broader issue than this question can address ;) $\endgroup$ Jan 14, 2016 at 9:02
  • $\begingroup$ I don't intend to tell you how to run your site, I'm a newb here. I apologise if I offended you. Some of the minds I found here impressed me. $\endgroup$
    – charmy
    Jan 14, 2016 at 9:11
  • 1
    $\begingroup$ OK, sorry for snark. My point was that all Stackexchange sites need quite clearly defined limits for what is "on topic", to keep them focused and useful. I think that the question I posed here - as to whether hypothetical alternate earths are on-topic - is a reasonable one; but the principle of having limits on topics is necessary, and a core part of Stackexchange. $\endgroup$ Jan 14, 2016 at 9:20
  • $\begingroup$ smiles, I've never been able to keep focus on one subject. Best ideas come from when I dont. Thats just me. $\endgroup$
    – charmy
    Jan 14, 2016 at 9:28
  • $\begingroup$ I still hold my view for all its worth tho. Unless this is the RCC, Let Galileo play. $\endgroup$
    – charmy
    Jan 14, 2016 at 9:32
  • $\begingroup$ wow just had two bounces, on id check. I'm not a threat! tho i'm glad i set them up now? $\endgroup$
    – charmy
    Jan 14, 2016 at 9:52

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