Explain to me again, how we know the Earth to be banana shaped.

Ratskinner said:

One big additional question would be: is the ringworld spinning? If so, the ringworld spinning gives you "days", while the sun's (slower) orbit gives "years". You'd have two times each year when the whole ring is plunged into a deeper darkness than it usually sees as the sun passes "behind" some portion of the ring and the Arc disappears from lack of illumination. I would expect those to be important times in people's lives.

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The simpler possibility is the ring spins around the sun, with plates in the sky to block sunlight and simulate light that spin in the opposite direction of the ground. Long-enough plates and with the right rotation speeds, you could replicate a day as we know it.

Celebrim said:

I don't think we actually know why things fall in a D&D world. Possible explanations:

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My favorite pseudo-scientific explanation for gravity is that it's a matter of evolution. All the things that didn't fall down have long since fallen off the face of the Earth.

As for the issue of helio- versus geocentrism, The two main things that turned the western world to heliocentrism was:

1. The really complex formulae astronomers were using to calculate the position of the planets, with epicycles and other weird stuff. Then Copernicus showed (probably with some influence from Arabic astronomers) that if you instead put the Sun at the center, everything fell neatly into simple formulae (well, almost - he didn't get the subtleties of elliptical rather than circular orbits, but that's a matter of fine tuning).

2. Galileo Galilei observing the moons of Jupiter, thereby establishing that it was possible for things to orbit something other than the Earth. He also observed that Venus had phases, just like the moon.

Ratskinner said:

That would be really visually weird for earthers to experience. There'd (almost) always be the "Great Arc of the Sky" (far side of the ring) at night, that would only briefly go dark in a regular pattern. (And how much detail you could see of it would depend on the dimensions of the ring. Additionally, days and nights wouldn't need to be the anywhere near same or even regular length.

The first big question I think of is "what angle does the axis of the solar orbit make with ring's axis?" That will determine what odd-to-earthlings path the sun takes across the sky. Also

One big additional question would be: is the ringworld spinning? If so, the ringworld spinning gives you "days", while the sun's (slower) orbit gives "years". You'd have two times each year when the whole ring is plunged into a deeper darkness than it usually sees as the sun passes "behind" some portion of the ring and the Arc disappears from lack of illumination. I would expect those to be important times in people's lives.

If the solar orbit and ringworld rotation are at the same period, you would have permanently cold "polar" regions and warm "tropical" regions along the ring.

The more I think about it, the weirder it gets (lotsa possibilities here).

Click to expand...

Well the really weird bit would be that the sun is outside the ring, instead of at the center. And most creatures live on the outer side of the ring, instead of the inner side (as they do with Larry Niven's Ringworld). The inner side of the ring would be in perpetual night, as the sun is always blocked by the ring. Creatures that prefer darkness would live there (perhaps drow - not living in caves, but in a world that perpetually has a night sky and the Great Arch). Those on the outer side of the ring wouldn't see the "Great Arch" because it would be beneath their feet.

You could even have something bizarre like a black sun in the center of the ring.

Caliban said:

Well the really weird bit would be that the sun is outside the ring, instead of at the center. And most creatures live on the outer side of the ring, instead of the inner side (as they do with Larry Niven's Ringworld). The inner side of the ring would be in perpetual night, as the sun is always blocked by the ring. Creatures that prefer darkness would live there (perhaps drow - not living in caves, but in a world that perpetually has a night sky and the Great Arch). Those on the outer side of the ring wouldn't see the "Great Arch" because it would be beneath their feet.

You could even have something bizarre like a black sun in the center of the ring.

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Ooh, nice - an Underdark that isn't underground, but is still perpetually dark and most definitely underneath. That is a really cool concept.

MarkB said:

Ooh, nice - an Underdark that isn't underground, but is still perpetually dark and most definitely underneath. That is a really cool concept.

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Yeah. You could even associate darkvision with the dark sun on the inside of the ring, so that it works on the dark side, but not underground. A neat little twist on it.

Maxperson said:

Yeah. You could even associate darkvision with the dark sun on the inside of the ring, so that it works on the dark side, but not underground. A neat little twist on it.

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You could even set up the size and position of the outer sun so that, from the viewpoint of the underside, it would become just perfectly eclipsed when it was directly overhead on the far side of the ring.

It still wouldn't shed any significant light on the inside, but at that point you'd be just barely able to see the corona and any major prominences - just a hint, tantalising to any surfacers down there and infuriating to the Drow, of what real sunlight looks like.

That way, you can still have the same day-cycle for the Underdark as for the world above. Also, you could have solar flares being an occasional calamitous event for the Underdark, briefly illuminating it with something approaching true daylight.

Staffan said:

My favorite pseudo-scientific explanation for gravity is that it's a matter of evolution. All the things that didn't fall down have long since fallen off the face of the Earth.

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As a point of fact, all the free hydrogen that didn't bind with oxygen has long since fallen off the face of the Earth. As did most of the Helium. The Helium you fill up balloons with quite soon after floats into the upper atmosphere and gets blown off by the solar wind. So in a sense...as it applies to the elemental composition of the Earth...

As for the issue of helio- versus geocentrism, The two main things that turned the western world to heliocentrism was:

1. The really complex formulae astronomers were using to calculate the position of the planets, with epicycles and other weird stuff. Then Copernicus showed (probably with some influence from Arabic astronomers) that if you instead put the Sun at the center, everything fell neatly into simple formulae (well, almost - he didn't get the subtleties of elliptical rather than circular orbits, but that's a matter of fine tuning).

2. Galileo Galilei observing the moons of Jupiter, thereby establishing that it was possible for things to orbit something other than the Earth. He also observed that Venus had phases, just like the moon.

Click to expand...

We don't know in the D&D world what observations astronomers make. The 'fixed' stars under magnification might not resolve to points. Planets - if planets even exist in the skies over a given D&D setting - may not have their own orbiting bodies, and presumably (as in Greyhawk) don't have phases of their own. Those planets don't demonstrate retrograde orbits from the perspective of an observer on Earth, and so forth.

Perhaps, if you drop weights into clay, the penetration into the clay will be linear with both mass and velocity. If you grind a cannon underwater, eventually the water will stop heating up. If you carefully burn a consumable with a known weight, and collect all the by products, you'll find there is less total mass rather than more. Meat left in a sealed chamber will spontaneously erupt in maggots. And so on and so forth.

We don't actually see these tests performed in D&D, so we don't know how they work out. But we have no reason to suppose that they will work out as they do in our world, and some good reasons to suppose that they work out quite differently.

Celebrim said:

As a point of fact, all the free hydrogen that didn't bind with oxygen has long since fallen off the face of the Earth. As did most of the Helium. The Helium you fill up balloons with quite soon after floats into the upper atmosphere and gets blown off by the solar wind. So in a sense...as it applies to the elemental composition of the Earth...

Click to expand...

That's more a matter of buoyancy than gravity, but point taken.

We don't know in the D&D world what observations astronomers make. The 'fixed' stars under magnification might not resolve to points. Planets - if planets even exist in the skies over a given D&D setting - may not have their own orbiting bodies, and presumably (as in Greyhawk) don't have phases of their own. Those planets don't demonstrate retrograde orbits from the perspective of an observer on Earth, and so forth.

Click to expand...

That bit was in response to the OP's: "I presume that the our own real-world ancients worked out that it wasn't through some observational means that distinguishes the earth going around the Sun from the other wary around. What was that?"

Basically, the issue of whether the Sun revolves around the Earth or vice versa is, in itself, rather pointless (and technically, in the real world they're both orbiting a point somewhere in between, though this point lies inside the Sun but not at its center). The thing that made astronomers and then other people switch to the heliocentric world-view was the way other things moved, and that things were much simpler when you looked at them from the heliocentric perspective. There was actually a "compromise" worldview put forward by Tycho Brahe that stated that the Sun and the Moon revolved around the Earth, but all the planets revolved around the Sun.

Another version - this one requires a much smaller ring, and you don't have the issues of a tiny orbiting sun. The sun is normal size, and the ring orbits the sun, with the "black sun" at the center of the ring. Its an [artifact/natural magical phenomena/god] that is responsible for keeping the ring stable. (Perhaps a magical version of a black hole, and instead of an accretion disk the debris forms into a habitable structure. It would literally be a black hole sun.)

The ring spins to give day/night cycles and you still have the inner ring civilizations in perpetual night, but with the glow around the edges when the sun is opposite them and occluded by the ring. Perhaps the areas near the edge are considered hostile because of they get regularly bathed in sunlight around the edge of the ring.

Ratskinner said:

That would be really visually weird for earthers to experience. There'd (almost) always be the "Great Arc of the Sky" (far side of the ring) at night, that would only briefly go dark in a regular pattern. (And how much detail you could see of it would depend on the dimensions of the ring. Additionally, days and nights wouldn't need to be the anywhere near same or even regular length.

The first big question I think of is "what angle does the axis of the solar orbit make with ring's axis?" That will determine what odd-to-earthlings path the sun takes across the sky. Also

One big additional question would be: is the ringworld spinning? If so, the ringworld spinning gives you "days", while the sun's (slower) orbit gives "years". You'd have two times each year when the whole ring is plunged into a deeper darkness than it usually sees as the sun passes "behind" some portion of the ring and the Arc disappears from lack of illumination. I would expect those to be important times in people's lives.

If the solar orbit and ringworld rotation are at the same period, you would have permanently cold "polar" regions and warm "tropical" regions along the ring.

The more I think about it, the weirder it gets (lotsa possibilities here).

Click to expand...

See now THAT is exactly the sort of thing a DM needs to catch before their players do. If you had the Sun (which also orbits a central axis) on a slight axial tilt to the world's own, then you could get the effect of the Sun being higher and lower in the sky at different points of the year. But I assumed in Caliban's example that the people were living on the outer face of the ring and you seem to have them on the inner face. I like them on the outer face then you have can have some central point in the middle that everything is drawn to so that if you go off the North or South edge, you fall towards it. Not sure what could be at the exact centre of everything but I'm provisionally going to say "The Abyss".

EDIT: I should have read further...

Caliban said:

Well the really weird bit would be that the sun is outside the ring, instead of at the center. And most creatures live on the outer side of the ring, instead of the inner side (as they do with Larry Niven's Ringworld). The inner side of the ring would be in perpetual night, as the sun is always blocked by the ring. Creatures that prefer darkness would live there (perhaps drow - not living in caves, but in a world that perpetually has a night sky and the Great Arch). Those on the outer side of the ring wouldn't see the "Great Arch" because it would be beneath their feet.

You could even have something bizarre like a black sun in the center of the ring.

Click to expand...

So now I get why the assumption is that people lived on the inside of the ring - because there was also the assumption that the Sun is in the centre. An assumption which I did not share. Hmmm. I like the idea of the Sun on the outside. If you combine it with the axial tilt though, you lose the "eternal darkness" part. On the plus side, you could - depending on how extreme that axial tilt was and how wide the world was (Ha! Brings new meaning to the term "the whole, wide world.") get gradiations of the "underdark". I.e. there would be two regions at the North and the South that got periods of light but as you crept closer to the meridian you'd approach regions of perma-darkness. Which could be great for DMs making up ecosystems of monsters and kingdoms.

The big question is then how thick the world is. Can you climb over the "top" to reach the other side? If so what is on the surface of the edge? Or maybe more exciting would be if you descended tunnels until you came out of the other side.

Woah! Imagine if you were a player in a game and you didn't know the cosmology and your DM sprung that on you - descending ever deeper into the Underdark, until you saw some the dim, purple light of dawn and emerged from some cave onto the otherside of the world! Mind-blowing. Somebody has to do this to their group.!

Celebrim said:

We don't know in the D&D world what observations astronomers make. The 'fixed' stars under magnification might not resolve to points. Planets - if planets even exist in the skies over a given D&D setting - may not have their own orbiting bodies, and presumably (as in Greyhawk) don't have phases of their own. Those planets don't demonstrate retrograde orbits from the perspective of an observer on Earth, and so forth.

Perhaps, if you drop weights into clay, the penetration into the clay will be linear with both mass and velocity. If you grind a cannon underwater, eventually the water will stop heating up. If you carefully burn a consumable with a known weight, and collect all the by products, you'll find there is less total mass rather than more. Meat left in a sealed chamber will spontaneously erupt in maggots. And so on and so forth.

We don't actually see these tests performed in D&D, so we don't know how they work out. But we have no reason to suppose that they will work out as they do in our world, and some good reasons to suppose that they work out quite differently.

Click to expand...

I like the Spontaneous Generation reference. All of this is good. I think the key thing is internal consistency. Good fiction can play with any sorts of rules so long as it's internally consistent about it. We've all condemned some film or book for selectively using some power or conceit when it's useful to the plot and then conveniently forgetting someone can do something when it would spoil their cool idea. The dangerous ones, are the ones that seem simple, ime. The above are some good examples. They remind me of that scene in the movie Rosencrantz and Guildenstern are Dead where Gary Oldman playing Rosencrantz (or possibly Guildenstern) standing on a balcony pulls out a cricket ball and a feather and announces "Now you would imagine that these two objects would fall at a different speed..." and proceeds to drop them to the tennis court below. "...and you'd be absolutely right."