I try to imagine that the prime material plane is as infinite as the universe which is described in modern cosmology. Exactly how infinite that is depends on who you ask--I recommend PBS Spacetime on youtube for some accessible explanations. I do that for a couple of reasons--one, it gives me the largest possible sandbox for adventures set on the prime material. Two, it doesn't create the problem of needing to reinvent physics. Three, it lets players employ their knowledge in order to fill in blanks.
Like all the D&D planes the material is essentially infinite, all of the different official ( and homebrewed) worlds can be considered to be parts of it. This is really the Spelljammer ideal with the voids of empty space with the astral ( see the science spoiler below). The upcoming planescape will (hopefully) take this on in a meaningful way but we will have to wait and see.
Most folks have a huge problem visualizing the actual size of the visible universe (more on “visible later). To try to get even a slight feel scientists use a a measure called a lightyear, the distance light travels in a vacuum over the course of a year. The speed of light is 300,000 kilometers/second or 186,000 miles/second so a lightyear represents a distance of not quit 6 trillion miles or not quite 9.5 trillion kilometers. (I’ll use 6 trillion mi or 9.5 trillion km as the round numbers from here on). The nearest star (proxima centari) is 4.2 LY away that is 25.2 trillion miles or @40 trillion km. Stepping out further the solar system is about 25,000 Ly from the center of our Milky Way galaxy - 150 Quadrillion miles/237.5 Quadrillion km. (Starting to get overwhelmed yet?) The Milky Way Galaxy holds roughly 300 Billion stars an enough gas and dust to make 200-300 billion more. It’s approximately 100,000 lightyears in diameter. The nearest large galaxy to it is the Andromeda galaxy which is slightly larger and about 2.5 million LY from us. Of course since light takes time to travel we see andromeda not as it is now, but as it was 2.5 million years ago. This also applies to more distant objects, the most distant objects we can see are young galaxies about 13 billion years old so we often describe them as being 13 billion light years away - but this is technically wrong as the (visible) universe has been expanding all that time. The edge of the visible universe (which we see in all directions) represents the point in time roughly 300,000 years after the Big Bang when the u inverse had cooled enough for atoms to form and light and matter separated . That point was roughly 13.7 billion years ago. However, because of the ongoing expansion of the universe those light waves have been stretched tremendously and the actual (estimated) current distance to those objects is such that instead of being roughly 27.4 billion lightyears in diameter the visible section of the universe is @94 billion LY in diameter. And that is just the visible portion why do I say visible? Because there is significant evidence from both astronomy and particle physics to suggest that it must be much bigger in actual fact and may actually be infinite in size. Everything we see says the universe is “flat” that is there is no overall curvature to space-time. But just like on earth where in the roughly 5 mile diameter range that a 6’ tall person can see the earth looks flat but when we move away from the surface we can see that it is actually curved (and there is visible evidence of this if we understand it even from the ground). Is it curved? We will probably never know as we would need many orders of magnitude more precise measures to be able to tell.
so for ease of math we will call the current universe 100 billion LY in diameter, making it 6x10^23 miles across or 9.5 x 10^23 km across - no wonder folks have a hard time picturing it’s size - and that is only the visible part of what may be an infinite in all directions plane.
Isn't the DnD world flat because if you look at the physical book it's plat but other parts aren't they're more like cylinders which shows they couldv'e made it round but chose to make it flat.
The world in D&D is whatever shape the person doing the world building wants it to be. Flat (with or without giant turtle), round, a hollow sphere with creatures living inside it, an icosahedron, a functionally infinite plane, a giant tree growing in space....
Most of the published worlds are globes. They often present the prime material plane as a disc in illustrations of the multiverse, but none of the planes in that are the shape they are in the chart -- it's an illustration of the relationship of the planes. (Of course, if you want them to be that shape, they're that shape.)
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Is the material plane the same size as earth? And I mean the main planet of the material plane because I know it has pace and all that.
I try to imagine that the prime material plane is as infinite as the universe which is described in modern cosmology. Exactly how infinite that is depends on who you ask--I recommend PBS Spacetime on youtube for some accessible explanations. I do that for a couple of reasons--one, it gives me the largest possible sandbox for adventures set on the prime material. Two, it doesn't create the problem of needing to reinvent physics. Three, it lets players employ their knowledge in order to fill in blanks.
Like all the D&D planes the material is essentially infinite, all of the different official ( and homebrewed) worlds can be considered to be parts of it. This is really the Spelljammer ideal with the voids of empty space with the astral ( see the science spoiler below). The upcoming planescape will (hopefully) take this on in a meaningful way but we will have to wait and see.
Most folks have a huge problem visualizing the actual size of the visible universe (more on “visible later). To try to get even a slight feel scientists use a a measure called a lightyear, the distance light travels in a vacuum over the course of a year. The speed of light is 300,000 kilometers/second or 186,000 miles/second so a lightyear represents a distance of not quit 6 trillion miles or not quite 9.5 trillion kilometers. (I’ll use 6 trillion mi or 9.5 trillion km as the round numbers from here on). The nearest star (proxima centari) is 4.2 LY away that is 25.2 trillion miles or @40 trillion km. Stepping out further the solar system is about 25,000 Ly from the center of our Milky Way galaxy - 150 Quadrillion miles/237.5 Quadrillion km. (Starting to get overwhelmed yet?) The Milky Way Galaxy holds roughly 300 Billion stars an enough gas and dust to make 200-300 billion more. It’s approximately 100,000 lightyears in diameter. The nearest large galaxy to it is the Andromeda galaxy which is slightly larger and about 2.5 million LY from us. Of course since light takes time to travel we see andromeda not as it is now, but as it was 2.5 million years ago. This also applies to more distant objects, the most distant objects we can see are young galaxies about 13 billion years old so we often describe them as being 13 billion light years away - but this is technically wrong as the (visible) universe has been expanding all that time. The edge of the visible universe (which we see in all directions) represents the point in time roughly 300,000 years after the Big Bang when the u inverse had cooled enough for atoms to form and light and matter separated . That point was roughly 13.7 billion years ago. However, because of the ongoing expansion of the universe those light waves have been stretched tremendously and the actual (estimated) current distance to those objects is such that instead of being roughly 27.4 billion lightyears in diameter the visible section of the universe is @94 billion LY in diameter.
And that is just the visible portion why do I say visible? Because there is significant evidence from both astronomy and particle physics to suggest that it must be much bigger in actual fact and may actually be infinite in size. Everything we see says the universe is “flat” that is there is no overall curvature to space-time. But just like on earth where in the roughly 5 mile diameter range that a 6’ tall person can see the earth looks flat but when we move away from the surface we can see that it is actually curved (and there is visible evidence of this if we understand it even from the ground). Is it curved? We will probably never know as we would need many orders of magnitude more precise measures to be able to tell.
so for ease of math we will call the current universe 100 billion LY in diameter, making it 6x10^23 miles across or 9.5 x 10^23 km across - no wonder folks have a hard time picturing it’s size - and that is only the visible part of what may be an infinite in all directions plane.
Wisea$$ DM and Player since 1979.
If you mean the main planet, that depends on which campaign setting, since they are all on different planets. From my quick digging:
Toril (main planet of the Forgotten Realms setting, where most of the adventures & recent movie take place): Virtually the exact same size as Earth
Eberron: About 2/3 the size of Earth
Krynn (aka Dragonlance planet): A little larger than our Moon
Exandria (Critical Role world, in the Wildemount book): A little larger than our Moon
I'm a bit more iffy on the Magic: The Gathering worlds, but from what I could find off hand...
Theros: Much larger than Earth, not quite double the size of Earth (also it might be a flat disc, apparently?)
Ravnica: Possibly about the same size as our Moon (???)
Now the Material Plane is the plane of existence that includes ALL of these worlds and countless more. So it is likely infinite in size.
Isn't the DnD world flat because if you look at the physical book it's plat but other parts aren't they're more like cylinders which shows they couldv'e made it round but chose to make it flat.
The world in D&D is whatever shape the person doing the world building wants it to be. Flat (with or without giant turtle), round, a hollow sphere with creatures living inside it, an icosahedron, a functionally infinite plane, a giant tree growing in space....
Most of the published worlds are globes. They often present the prime material plane as a disc in illustrations of the multiverse, but none of the planes in that are the shape they are in the chart -- it's an illustration of the relationship of the planes. (Of course, if you want them to be that shape, they're that shape.)