Night And Day In The Hollow Earth

So I'm trying to put together a hollow earth-type setting, but I keep running into a big problem: I want there to be a night and day cycle like we have in the real world. Since there's nowhere for the sun to hide, this is a bit of a problem. Thoughts? Suggestions?

A big hemispherical sunshade? Sorry, but you've somewhat written yourself into a hole with that one.

edited 20th Aug '10 10:11:17 AM by Yej

Da Rules excuse all the inaccuracy in the world. Listen to them, not me.

The sun could regularly dim and light up.

Is it possible to measure the hollow earth? I'm asking because I thought maybe Sufficiently Advanced Aliens (or Precursors) could have made a half Dyson Sphere that revolves around the sun, giving shade equal lengths of time as well as giving them solar power.

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...lots and lots of cyclically luminescent fungus? I just like the idea of someone going "Now, Timmy, be home before the fungus dim."

i. hear. a. sound.

If they moved into the hollow earth from the surface, just say they designed their light source to be like the one they were used to.

I really should have mentioned this in my OP, but this is intended to be more of a sword and sorcery setting than a sci-fi one. And thanks for all the replies so far!

Here, I'll show you guys some of the ideas I've had to get around the problem. None of them are perfect, but it's enough to give me hope that there's a solution to the problem.

Solution A. There's a small planetoid that orbits the Inner Sun. Problem: It would only create short eclipses, not nighttime conditions and it would only create total darkness along a band across the circumference of the hollow earth.

Solution B. The Inner Sun orbits around a much larger planetoid in the center of the hollow earth. Problem: I think the planetoid would have to be pretty huge, which would detract significantly from what I had in mind for the setting.

Solution C: The Inner Sun comes in and out of an opening at one of the poles. Problem: Where does it go?

Solution D: The Inner Sun turns on and off. Problem: It feels like a lazy cop out.

Any ideas?

What do you mean by a hollow earth? Are you talking about a Dyson sphere here?

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http://en.wikipedia.org/wiki/Hollow_Earth

is the sun a actual star?

make the sun a kind of planetoid of unique properties, one side is dark and the other is bright, with the difference between the two being very blurred so when the sun rotates it creates the progressive night and day cycle.

"Here to welcome our new golden-eyed overlords," said Addy promptly.

The sun could be artificial and regulated by humans. Perhaps they lived on a surface world at some point or another and constructed a substitute sun out of nostalgia. If it's a real star (or something similar) than you've got a problem, but what if the sun is nothing but a giant sun lamp? It could provide heat and light and be controlled quite precisely, even creating the illusion of seasons.

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With some fleshing out, the "just turning on and off" thing could be an interesting idea.

For example, in Shin Megami Tensei Nocturne, a game set in a hollow earth, the light source in the middle would ebb and flow much like a lunar cycle (though much faster) and its phase was related to a variety of factors.

Perhaps magic can ebb and flow a little bit, and at "high tide" of sorts, when the "sun" is brightest, magic, or perhaps one variety of magic, could be at high power, while at "low tide" it's the opposite, either magic is harder or one type of magic is more powerful while the others are less so.

Maybe the "sun" could be a portal through which power is flowing from somewhere else, into the hollow world.

So if I'm understanding correctly, we're talking about something akin to a mini-dyson sphere? (ie. A hollow planet where the gravity is in reverse to a normal planet, so everything is held down to the inner surface, with a smaller sun-like light/heat source in the middle?)

The problem I can see with the idea of having some sort of object orbit the inner star to block out its light, or having a dark side to the sun, is that it still probably wouldn't achieve a real "night" effect. We get night because our planet is actually facing away from the sun, but as you can see with the moon, it's still quite capable of reflecting its light onto objects that we are facing. So even if your inner sun has a dark side or an object blocking its light, it's still going to be reflecting it's light off of the other side of the hollow world. The resulting light level would be like the moon filling our entire sky at night. Not as bright as the day, but certainly much brighter than what we would consider to be night.

I agree that the "just turning off" sounds a little like a cop out on its own, but if there's an explained reason behind it, it could be made to work. I mean the hollow earth thing is already sort of independent of real physics, so you might not need more than a handwave to justify it working like that.

edited 25th Aug '10 2:44:23 PM by Stranger

Another option: Every day, a huge monster swallows the sun. It keeps it within for the night, and then expels it.

Maybe because it's necessary for the world, maybe because it's necessary for its own bodily functions.

The first question that you must ask yourself: does sun have to be a huge ball of flaming gases? As I don't know much about the story you're trying to write, I can't really tell what solution would be too sf or too fantastic. I think that the idea of "sun as an organism" could really solve the problem, whether it would be an ancient glowing monster or some other kind of organism.

You could say that the sun literally burns out every night and has to be replaced by some sort of organization or god-type thingy.

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Personally I kind of like the image of multiple moons orbiting the sun, netting a "night" of one solar eclipse after another. You could even have moons of different sizes or colors if you want.

Magic cyclicly lumenesciant fungus.

Alternativly, A Wizard Did It.

A slowly rotating magic or science based semispherical spotlight with the other half as a non-lit material, this would cause a few problems at the poles though...

It's clearly a case of backroom political albumizing.

does there need to be day and night? in fantasy settings how do dwarf cope with living under ground? most of the time they A) dont need light so theyre effectively happy to be blind while underground B) can work in very low light due too specially adapted eyes C) they have lots of lanterns

• i like the bioluminescent fungus idea

it would also be cool if you could travel there(to the fungusun that is) new wildlife? hypermagical enviroment?

edited 6th Nov '10 8:34:34 AM by Kalkiran

howsabout a realistc comprimise?

There is a sun in the core of the hollow earth,but it's quite dim. rather than any day or night, everything is in a sort of perpetual twighlight.

Bioluminicent Fungus! On another hand, it could be what the post directly above me said...

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Maybe there's a forest of fungi and the light 'migrates' through the forest. So if you recorded it from above and sped it up a lot it would look like waves of light or the northern lights It'd be like day and night, but would create a neat ecosystem.

Oh and I don't mean small patches of light, I mean real big ones, and it's a slow gradual thing with fading, not just like flicking about.

Woah, I was having the same problem and came across some similar answers. This might be a bit too sci-fi for a swords and sorcery setting, but have heard about concave earth theory. Its an offshoot of the whole flat earth thing. Anywho, one of their theories (and there are a bunch of them) is that all of space is inside the planet, and that the day night cycle is kind of an optical illusion in that the sun orbits around "space" and that the light cant pass through it, and thats why it appears dark.

I think i might be exsplaning it poorly, but its some interesting stuff. Good for insperation in any case.

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How about a 'big bowl of magic' fire that orbits around the 'center' of the hollow world, with its dark side facing the closest surface so that it lights up the far side. This would also give it the effect of setting... kinda.

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