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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?

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    $\begingroup$ 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