What if the world was flat?

[Fnord]

So I am more of a table-top gamer than a writer (though I write a fair amount of short stories that take place in the work-in-progress world I have designed). In trying to fine-tune the actual cosmology of the world (there's plenty of differing creation myths based on culture, but the theme of the game is finding the actual truth) it seemed to make sense, given all the other stuff involved, to attempt to make the world actually flat (or more accurately, a flat disc inside of a sphere not unlike the structure of a gyroscope).

Now the players all assume the world is round. I'm not looking at making it scientifically perfect in regards to things like gravity and seasons (it is fantasy after all), but what other subtle differences could I sprinkle about as clues (at least until the player-characters discover and dissect the ancient astrolabe puzzle thing that shows the total "unification" of the cosmos and gods) that the world isn't actually round? What are some scientific implications of such a place that I might toy with?

[Devor]

What are some scientific implications of such a place that I might toy with?

The horizon, for a start. Objects in space and the sun rotating overhead in the sphere would move a lot differently. I'm wondering if it would affect the climate and weather patterns in a way that's distinctive or not. Tides would be based on the rotations of the plane instead of the moon. I don't know if the characters would necessarily notice any of these.

The big question is what happens on the edge, and what's on the other side of the disk. If there's a gap between the edge of the plane and the sphere, you might have things falling over the side - maybe rain is caused by water draining over the edge and whooshing around the sphere unsettled. Maybe there's no gap, and you can walk to the edge and touch the moving walls. You need to figure out some of the implications to those possibilities.

[SeverinR]

We had a post that included something like this recently but couldn't find it.
One problem with a flat world...Does the sun set? Or is it day all the time? Does it tumble end over end, so there is a day and night? Slow tumble could make day period longer then earths.
They offered a flat spin rotation idea, but that doesn't really fix the day/night thing. It could make for a bright/warm time(closest to the sun)and a cool dimmer time.(away from sun)
How does weather move around?
How does the inhabitants differ on a flat planet compared to a round spinning one?
I believe a flat home planet can work, but some basic reasons need to available, so even if not specified, you can describe it correctly with a reason in mind.

[grahamguitarman]

Actually the horizon would not look any different till you got closer to the edge of the world. I know this because I spent two years studying the science of perspective in minute detail. Until the edge comes within viewing distance it would initially be at the same height within the field of vision - eye level. Because of the geometry of vision, the horizon is always at eye level (a simple way to test this is to look out to the sea and then crouch, as you crouch the horizon level will drop with you).

So to begin with the Horizon will be where it usually is on a round world. But as you get within viewing distance of the edge, the horizon would seem to get lower within the field of vision. The visible horizon will continue to get gradually lower in the field of vision, until it becomes visually obvious that there is a drop beyond the edge of the world.

If there was a mountain range at the edge of the world though, you would not even see the horizon so this visual effect would not be seen.

[Devor]

I thought there were issues of objects moving on the horizon? I thoughtful I remember something about Columbus watching boats tilting downward as they vanished at sea. I was vague, though, because I wasn't sure the impact.

[Fnord]

The horizon, for a start. Objects in space and the sun rotating overhead in the sphere would move a lot differently. I'm wondering if it would affect the climate and weather patterns in a way that's distinctive or not. Tides would be based on the rotations of the plane instead of the moon. I don't know if the characters would necessarily notice any of these.

The big question is what happens on the edge, and what's on the other side of the disk. If there's a gap between the edge of the plane and the sphere, you might have things falling over the side - maybe rain is caused by water draining over the edge and whooshing around the sphere unsettled. Maybe there's no gap, and you can walk to the edge and touch the moving walls. You need to figure out some of the implications to those possibilities.

The horizon was the first thing I thought about and I had trouble visualizing how that would look. The world was battered by a cataclysm/reckoning/insert-your-own-trope-here about a millennium ago and thus it is very "young mountainous", especially where the characters are, so the horizon isn't all that obvious anyway. But they will soon ascend to the top of the tallest mountain and it may be more apparent. i remember standing at the top of Scottsbluff in Western Nebraska and really being able to see the curve of the earth. It was pretty crazy. It's hard to picture in my head seeing even further.

[Fnord]

Actually the horizon would not look any different till you got closer to the edge of the world. I know this because I spent two years studying the science of perspective in minute detail. Until the edge comes within viewing distance it would initially be at the same height within the field of vision - eye level. Because of the geometry of vision, the horizon is always at eye level (a simple way to test this is to look out to the sea and then crouch, as you crouch the horizon level will drop with you).

So to begin with the Horizon will be where it usually is on a round world. But as you get within viewing distance of the edge, the horizon would seem to get lower within the field of vision. The visible horizon will continue to get gradually lower in the field of vision, until it becomes visually obvious that there is a drop beyond the edge of the world.

If there was a mountain range at the edge of the world though, you would not even see the horizon so this visual effect would not be seen.

Awesome, I typed my response before I saw this. Thanks, that's one of things I was curious about.

As to the edge, it's kind of hard to explain--as you approach any of the edges of the terrestrial world you actually get closer to one of the four "land-level" elder gods realms. The best way to visualize it would be a five-circle Venn diagram, with the "mortal world" in the center. So approaching the "edge" just eventually takes you into a realm that more reflects of the "domain" of the god in that given direction. So there isn't an edge, per se, in that you could approach and look over it. It's more of a boundary.

There is definitely an underside, a hellish realm that is in every way an "underworld". It was actually the first mortal realm, though I'm still fleshing that part of it out.

[Queshire]

If there's no edge, then would it matter or not if it was flat?

[Steerpike]

How thick is it? In other words, is there enough mass to retain an atmosphere and have the right gravity for the lifeforms on the surface?

[Queshire]

Er... If the world's flat to begin with I don't think scientific stuff such as gravity and atmosphere are a concern...