Why wouldn’t there be tides, if the sun is rotating around this earth?
Hey, I pretty sure that the tides are caused primarily by the MOON.
So depending where it was, you’d be getting flooded every other day if it still rotated aroung us.
But that wouldn’t matter, 'cos all the extra water would just dropp of the edge of the earth, la dee da…
The tidal locking I’m talking about has nothing to do with water. See here. There’s no water on our moon, and it is tidally locked with Earth.
Non-spheres (like disk worlds) would have a greater tendency to become tidally locked with other bodies because of torque from bulge dragging.
What would a flat world be like? Iowa.
The “front” and “back” are going to be pretty unpleasant places. Since the dome transmits UV light, they’re gonna be fried. Come to think about about it, that’s going to be the case pretty much everywhere at dawn and dusk, unless a passing wizard puts a heavy UV filter around base of the glass dome.
Look, you guys are still thinking that the “sun” is a star. It’s pretty clear the sun cannot be a star. It’s some other type of object. It seems to me that if it orbits around the disk every 24 hours and appears to be about the same size as Sol from Earth, the “sun” has to be smaller than the Moon, and closer to the disk than the Moon is from Earth. If it was about the same size as the Moon, it would have to be about the same distance from the Disk as the Moon is from Earth, and that would mean it would orbit the Disk in about 30 days. So–let’s call it “Helios”–Helios has to orbit the disk in 24 hours. Assuming the Disk has about the same mass as Earth, that means Helios has to be about the same distance from the Disk as a geostationary orbit.
On Earth geostationary orbits are 36,000 km above sea level. Add in another 6000 km for the radius of the Earth, and we see that geostationary orbits around an Earth-massed object are ~42,000 km from the center of gravity.
Couple more things.
Somebody is going to have to work out how large Helios must be if it’s 42,000 km above the center of gravity of the Disk and appears to be the same size as Sol. It’s going to be a pretty small object, much smaller than the Moon.
The tidal effects of Helios are going to be the same as Sol, assuming Helios has a similar density to Sol. If Sol were as dense as the Moon, it would exert the same tidal force. But since Sol is mostly hydrogen gas it is much less dense than the Moon and so has a much smaller tidal force. Therefore, if Helios has a similar composition as Sol, since it looks to be about the same size it would cause the same tides.
How those tides would work on a disk is hard to say exactly. And I agree that the disk is going to start spinning in sync with the orbit of Helios fairly quickly. The Earth won’t become tidally locked to the Moon or the Sun within the lifetime of the Earth, because it’s so massive in comparison to the tidal forces. But that disk is going to create huge tidal gradients. Maybe you’ll have to make Helios nearly massless
About the disk itself rotating with regard to the fixed stars, that’s certainly possible. You could give the disk any rotation you like. But then you screw up the notion that Helios is orbiting the Disk, because then the spin of the disk has to sync with the motion of Helios. And you don’t even have to spin it like a spinning coin, you can spin it like a record player, or some combination.
But this is nonsense. The whole point of a flat earth is that it doesn’t move. Do you feel any motion? No. Therefore, the earth doesn’t move. Period, end of story.
If the disk has a spin then you’re pretty much going to have to put Helios on tracks that run on top of the dome rather than try to orbit it because otherwise things get screwy.
Yes. And isn’t all this an exercise in suspension of disbelief? The question wasn’t, “how would it be possible from a physics/geophysics/astronomy pov.” This isn’t science fiction. The question is what would it be like, assuming that it’s just the way things were.
Never having a completely overcast sky (light almost always coming in from the edges) is a good start. You could also perhaps see lightning flashes at night from very, very far away, if you were reasonably high up. Also no timezones. Very simple astronomical calcs (not the very complex stuff that ancient civilizations loved spending time figuring out). The same stars in the same positions no matter your latitude (very unfortunate for navigation). And you couldn’t estimate the size of the earth the way the Greeks and others had done (so the most educated philosophers probably wouldn’t think it’s nearly as large as it actually is).
Not having a molten core at the planet’s center generating sufficient magnetic fields would be the death of your world as solar winds would simply blow any habitable atmosphere off into space.
No it won’t, because the light source for this world is not a star. It’s something else, something that is small enough to orbit the disk in ~24 hour and from the surface of the disk looks about the same size and puts out as much light as the Sun from Earth. Therefore, it has to be very small. Much smaller than the disk itself. Therefore, it’s not going to blast the atmosphere away into the void.
And besides, the disk has a transparent unobtanium dome over it, so the question is moot anyway.
Oh, and if we’re assuming that the disk gets its gravity from the 100 mile thick incredibly dense adamantium center of the disk, then both sides of the disk can be landscaped and you get twice as much habitable surface for almost the same cost. If you use artificial gravity then you don’t need the adamantium in the first place. Therefore, since we know that the disk WAS built with an adamantium core that is pretty good evidence that The Ancients didn’t use artificial gravity in the construction of the disk.
Please, let’s stop talking about the light source and the dome and the molten core and the cost of the thing 
This isn’t an engineering project. This isn’t even science fiction. This is just an imagining of what would things be like if the earth was flat like some ppl had assumed in the past.
The problem with having the sun be small and close is that then different parts of the disc are appreciably closer to the sun than others. Near the edges you’d have north and south “poles” that never get as warm as the rest of the disk, while the easternmost and westernmost edges would have extreme temperature fluctuations. Either this would be part of your setup, or else the sun would have to emit light and heat unsymmetrically, to make up for the geometry.
If you want an actual star, then the suggestion of just spinning the disk is a good one. The sun doesn’t orbit the disk, the disk just spins on it’s axis every 24 hours, and then you have day and night cycles just like on the earth.
But again, the problem with this is that the disk is spinning. A flat earth shouldn’t move. It should be imobile. This is the number one aesthetic reason to have a flat earth. Therefore all the other physics of the system depend on the disk not having any spin. Therefore the sun has to move around the disk. And if you want it to orbit, it’s got to be very small and very close. If you don’t like that, you’ve got to move the sun across the sky in some other way–on a chariot pulled by flaming swans is in fashion this epoch, I believe.