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A while ago I had an idea of a man made planet that consist of a thick, incredibly strong, outer crust, and at the core there is an antigravity/antimatter device that also produces consistent heat and light constantly. The crust is just at the point where the antigravity is about equal to earths gravity, and the people would live on the inside of the crust. It would have large shallow oceans, and a few continents. The flora and fauna is pretty standard, but because the entire planet is man made, there wouldn't be any large predators. Probably no mountains either, because the layer of liveable antigravity is small.

My question again is what would the weather be like in this sort of situation? There is no day/night heat change to cause pressure differences and therefore wind, and there's no rotation of the planet to cause wind or coriolis effect.

This idea isn't very well thought out yet, but I wondered if anyone had any thoughts on it.

Thanks

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  • $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Commented Oct 18, 2023 at 17:37
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    $\begingroup$ It almost sounded like you were describing Venus? $\endgroup$
    – Trevor
    Commented Oct 18, 2023 at 18:31
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    $\begingroup$ The more common description of your idea in the question body is "hollow Earth'" The use of anti-gravity to handle stuff gravitating to the crust is a bit different to the usual description. $\endgroup$
    – Gault Drakkor
    Commented Oct 18, 2023 at 21:12
  • $\begingroup$ relevant questions, worldbuilding.stackexchange.com/questions/17689/…. your main problem is keeping your interior cool enough. $\endgroup$
    – John
    Commented Oct 19, 2023 at 21:05
  • $\begingroup$ (a) You're describing a Dyson sphere with an artificial star. Judging the weather would require knowing the size of the sphere and artificial star, and the energy output of the artificial star. Gravity is an issue, you should read about the shell theorem. An oversimplification is that gravity inside the shell due to the shell is zero (the shell must rotate to create gravity). We have a LOT of Qs on this site about Dyson spheres. $\endgroup$
    – JBH
    Commented Oct 20, 2023 at 16:42

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Even with constant sun, there would be irregularities in the planet that would cause uneven heating which would lead to wind and other weather formation.

Differences in absorption vs reflection of light/heat on different terrain or biome. An ocean, a forest, or bare rock will absorb and reflect the light and heat very differently leading to some areas warming faster than others, this heat will drive wind to move the heat to the cooler areas, likely causing Hadley Cell like atmospheric mixing resulting in some circulation patterns. Weather itself will also have a similar effect. Clouds would shade areas, causing cooling.

Additionally, if I understand your description correctly they live inside a hollow planet with artificial gravity and sunlight. This would mean that the heat from the core-sun would ultimately be radiated through the ground to the outside of the planet. Differences in thermal conductivity of the planetary material would also lead to irregularities in heat distribution. The heat radiating from the outside of the planet wouldn't necessarily be evenly distributed either, I'm assuming this isn't a rogue planet and there is a normal sun that the planet is orbiting which means the outside of the planet would have hot and cold sides, which would affect the inside of the planet as well.

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  • $\begingroup$ Two faults: normally the crust is very slow to transfer heat, thus the inside would get HOT about to lava-high temperatures, and by his depiction, the gravity (outward) os stronger "up" from the surface, so the clouds won't go up, this would cause some other effects I can't even. $\endgroup$
    – Vesper
    Commented Oct 19, 2023 at 4:26
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    $\begingroup$ @Vesper Well, the planet's creators could build conductors into the crust, and put radiators on the outside of the shell with non-uniform spacing, and then you get "weather" (plus I like Josh's point about uneven heating from an external sun). Given the stated narrow zone of usable anti-grav, you're probably right about clouds though $\endgroup$
    – Auspex
    Commented Oct 19, 2023 at 13:51
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Edit: I misread the question. I thought it was about a planet with the suns on the outside. The question is just another Dyson sphere question ("...and at the core there is an antigravity/antimatter device that also produces consistent heat and light constantly"), and there's a high likelihood of this being a duplicate of a question already on the site.

It won't work

If I understand your question correctly, you're asking about an inside-out Dyson sphere. Rather than a shell around the sun, you have a planet surrounded on all sides by sunlight. In either case, inhabitants are living on the inside (in one way or another) of the sphere (be it the Dyson Sphere or your planet).

The Dyson sphere works because there's somewhere to send waste heat — outer space.

In the case of your idea, there's nowhere to put the waste heat. Those suns keep adding energy upon energy to the planet, but there's no where for the excess to go (via a night side). Even in the case of 100% perfect efficiency and a world coated with solar panels, your inhabitants wouldn't be capable of consuming all of the energy. It would eventually build up — most likely in the form of an oven.

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    $\begingroup$ thermodynamics say the planet will heat up until it is the same temperatures as the sun. $\endgroup$
    – John
    Commented Oct 18, 2023 at 22:17
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    $\begingroup$ @John No it wouldn't...because it's not a closed box. There is space between the suns and they are some distance away. It would get hot though. $\endgroup$
    – DKNguyen
    Commented Oct 18, 2023 at 23:40
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    $\begingroup$ @DKNguyen yes it will, it the only possible thermal equilibrium, it heats up until it is radiating at the same temperatures as the sun. It can only reach a cooler equilibrium if there is somewhere else for it to radiate heat too faster than it receives radiate heat, which it can't if the sun is heating all sides. Its just how thermal equilibrium works. Distance only changes how fast it reaches equilibrium not what that equilibrium is. $\endgroup$
    – John
    Commented Oct 19, 2023 at 0:25
  • $\begingroup$ @John "All sides" in this case means enough sides so it is always daylight, so six at most, and likely fewer, rather than a literal impenetrable shell of suns. So an oven yes, but the same temperature as the sun? No. $\endgroup$
    – DKNguyen
    Commented Oct 19, 2023 at 5:39
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    $\begingroup$ you didn't understand the q correctly. the "sun" is at the center of the sphere, not outside. $\endgroup$
    – ths
    Commented Oct 19, 2023 at 12:54

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