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First post (reposted and more focused). Thanks in advance. I'm working on an epic fantasy series where our future-Earth has gradually stopped spinning about its axis (though still about the sun). Assume magic/future-tech to allow for these assumptions: (1)Assume humans/animals/plants survived and are now thriving. (2) Assume 6 months of sun followed by 6 months of none; therefore we are NOT in a tidally-locked situation. (3) Assume one equitorial continent and a northern ocean and southern ocean. (4) Assume 4 "seasons" of dawn twilight, full day, dusk twilight, and full night.

My one focused question is what would the seasons be like weather-wise (along the equitorial continent)? Precipitation, temperature, etc.

Thanks.

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  • $\begingroup$ Welcome to world building. Please be sure to have a good understanding of the help center, where you can find our standards. In short: one question per post, question about worlbuilding, that can be answered in a measurable way and with a narrow enough scope. $\endgroup$ – L.Dutch - Reinstate Monica Sep 12 '20 at 16:50
  • $\begingroup$ (3) "The sun will appear..". Yes, the terminator will sweep the surface of the Earth in the opposite direction of how it appears to move today. On the other hand, the Sun rises in the East by definition. (Well, that used to be the case. I don't know about today.) (4) "How many centuries..." The rotational energy of the Earh is about 213,800 yottajoules (213.8E27 J). One megaton TNT equivalent (= one standard Russo-American thermonuclear bomb) is 4.184E15 J (4.184 petajoules). You can calculate how may of those per second you tolerate. $\endgroup$ – AlexP Sep 12 '20 at 17:07
  • $\begingroup$ Thanks for the feedback, everyone! $\endgroup$ – Twelvfth Sep 12 '20 at 23:54
  • $\begingroup$ @L.Dutch-ReinstateMonica Can this question be re-opened? The question has been edited to match the text of the question you just deleted, and I spent a long time on the answer you just deleted. $\endgroup$ – Ash Sep 13 '20 at 17:20
  • $\begingroup$ Ash, I didn't delete the old question. It was "closed" by admin. I retyped it to simplify it and waited 24 hours, but it wasn't un-"closed" so I just copy/pasted it into a new thread, as the admin had said I had the option to repost or edit the original. I'd love to hear your answer though! $\endgroup$ – Twelvfth Sep 13 '20 at 19:11
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I've never seen the word "Hellish" in so many academic papers.

Side note: The Earth will start spinning again:

The moon will start the rotation again. It will be slow, takes thousands of years, and wont get up to full 24-hour speed, but it will save us from the 12-month day, which, as you've probably guessed, is going to be hellish.

However, lets assume you've magic'd away the moon, then what:

Crippling hot summer. Very stormy.

The hot side gets very hot. Very very hot. The calculation is on Wikipedia but your day time temperature will peak at about 102 degrees Celsius (in the shade).

For those preferring freedom units, that's 215 F. You can boil water without a stove.

That temperature will evaporate water extremely quickly. That moist hot air will hit dry hot air and create extreme storms around the "midday" area. Those storms will block the sun in nearby areas, dropping the temperature, but creating more of a temperature gradient. I lack the imagination to predict how intense these storms will be, but "Hellish" seems like a safe bet.

Rocky or concrete ground that holds a lot of heat will get hit with rain, it will immediately evaporate, and fall back down again in a constant cycle. This cycle will make bigger and bigger hailstones each cycle. Basketball sized hailstones will probably result.

But fear not, some microbes will survive the heat, as well as any humans in deep underground bunkers.

The hottest temperature plant life has survived is 72 degree C, so no plants survive the summer.

Extremely stormy sunset

I lack the skill to predict exactly how stormy this will be. All the papers I read just say things like "hellish" rather than give a calculation of wind speed.

The wind will be strong enough to knock you over even if you're braced for it. Strong enough to blow over anything except reinforced concrete and very flexible things.

The rain will be intense and sudden, and then hail will fall. I don't think you'll get much nice puffy snow, the water will just fall to earth as chunks of ice.

Freezing cold winter

The moon and stars gives just over a million times less power than the sun, and it keeps getting colder over all 6 months. The equilibrium point works out to (~0.0006/5.6E-8)^(1/4), or 10 Kelvin. (-263 degrees C), it will never get there (heat will be sucked from the ground and ocean for all 6 months), but expect about -100 C. We could get "hail" made of carbon dioxide.

Petrol will freeze. Oil will freeze. Antifreeze will freeze.

The ocean will freeze down at a rate of about 5cm per day. By the end of winter the ice over the ocean will be about 8m thick.

And a hurricane, earthquake and flood all at once for sunrise.

Same intensity storms as sunset, but this time the frozen ground (which is frozen solid to a decent depth, below most existing foundations) now rapidly thaws. Water tables which had frozen will now thaw. This will destabilise the ground, structures will move, sink, and fall over.

All water has frozen, and starts thawing, however all the small creeks and streams will thaw before the big rivers - entire countries will be flooded by thawing water that can't fit into the frozen lakes and rivers.

Also the oceans will thaw top-down, so the rising ice will push thawed water up onto the land.

Oh, and the planet will be totally flat in a few centuries.

The freeze-thaw cycle is one of the best ways nature has to flatten landscapes. Water seeps into a crack in a rock. Freezes and expands, cracking the rock. The equator and tropics are usually free of this process.

However now you have a planet wide deep freeze and thaw cycle, every mountain will be reduced to gravel, and that gravel will be blown around the planet. The planet will eventually form a boring, uniform, sphere.

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  • $\begingroup$ Hey Ash. Thanks for your answer. It was amazingly detailed and I'm so grateful for it. Thank you. I will take some time to pull it apart and think about it some more, but one immediate follow-up question, if you're willing, would be to know whether there would be annual/regular storms/climate events. You detailed above the transitions between "seasons" (which I do appreciate), but I am wondering if there would be a thunderstorm every midday, or a prevailing wind "midnight"--> sunrise. Or something like that. Again, thanks for you answer and hope you don't mind sharing more. $\endgroup$ – Twelvfth Sep 13 '20 at 19:30
  • $\begingroup$ @Twelvfth there will be a prevailing wind night->day constantly. The storm at midday will be basically always there but greatly varying in intensity. $\endgroup$ – Ash Sep 13 '20 at 23:46
  • $\begingroup$ Thanks for you latest answer. Like I mentioned yesterday, I paused to collect some other ancillary questions. If you don't mind, your insight would be greatly apreciated! (1) Air Travel. Would high-altitude wind currents create favourable year-long travel conditions? (2) Sea travel, would there be a period or season that allows for easy/survivavable sea travel (along north or southern ocean) (3) what about magnetosphere and radiation? (4) what would the moon appear like? (5) mind sharing the academic papers you referenced? Perhaps I can figure something on my own, if no paywall. $\endgroup$ – Twelvfth Sep 14 '20 at 21:57

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