I've got questions I haven't been able to get a grip on for two different planets.

One has its axis at about 90deg (like Uranus), with day & year like Venus (day longer than year), orbiting a purple (brown) dwarf (not tidal locked), & one hemisphere always dark. I'm having trouble getting "seasons" & day length sorted. I picture seasons of "hot sunny", "cold sunny", "hot dark", & "cold dark". I also picture no (or very limited) wind, except a stratospheric wind that comes down at/near the terminator, like a curtain. Am I wrong? Did I miss anything?

The other is a world without oceans. I'm not after Arrakis; I want a quite lush surface. I'd like no surface water at all, but I'm concerned that makes evolution impossible. (I imagined using chemotrophs to get around it.) I want a "sea level" pressure of 2-6x Earth. If there's surface water, it'd be "above sea level", no? Or do I also get superheated water/steam below that? I picture "sea level" as a "cloud deck", where water runs off continents in waterfalls & vaporizes at the heat/pressure limit, forming permanent, global cloud. This separates the world into two societies/species, above/below the deck. I'm thinking below the deck, the air is dense enough for "swimming" or very large flying creatures; maybe not as big as blue whales, but maybe orca-sized. Any thoughts on the ecology & weather? Did I miss anything? (If it matters, my model is Earth, with no changes except as noted.)

In both cases, any suggestions on sources I can use, without needing to get a degree in the relevant science?


closed as too broad by Renan, elemtilas, Cyn, Measure of despare., Ash May 1 at 12:33

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 4
    $\begingroup$ Two different questions. First one can be by itself. Second needs to contain a specific question. $\endgroup$ – Willk May 1 at 1:01
  • $\begingroup$ Good questions, but please ask one question per post. $\endgroup$ – Renan May 1 at 1:28
  • $\begingroup$ If your planet’s axis is at 90° then it can’t have a light and dark hemisphere. One hemisphere will be lit at one solstice, and the other hemisphere will be lit at the other solstice. $\endgroup$ – Mike Scott May 1 at 5:08
  • $\begingroup$ For the second question, a look at the phase diagram of water might help. $\endgroup$ – AtmosphericPrisonEscape May 1 at 12:47
  • $\begingroup$ worldbuilding.stackexchange.com/a/145947/58321 Shameless self promotion, but my answer here seems related to the weather on the 90°-tilt-world. $\endgroup$ – TheDyingOfLight May 1 at 17:24