Astronomy question

[Baron Opal]

Setting up my Aristotelian cosmology here...

Given that:

1) The visible planets are all approximatly the same size as Earth.
2) The apparent size is the same as here.
3) The apparent brightness is the same as here.
4) The solar system is Earth-centric.

How far away are the respective planets?

 

[The Sigil]

Just want a couple of points of clarification:

1.) Are you trying to set up a cosmological model of the actual solar system (i.e., with "Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, X" as your planets?

2.) Per your point #1 - is "Jupiter" not REALLY a gas giant but actually the same size as earth?

3.) The apparent size being the same - I presume you want the same approximate arcseconds in the sky (e.g., Mars is about 20 arcseconds at closest approach). For the naked eye, this won't matter much though - planets are more or less "points."

4.) Apparent brightness same as now - okay. Can "fiddle" with that.

5.) Earth-centric... do you include Sol (the sun) as orbiting?

6.) Is a "first order approximation" (with perfect circles for orbits instead of ellipses) okay? This will cause no variations in size/brightness (with elliptical orbits you get slight variations), but will be a *lot* easier to come up with! (One supposes you could later add Aristotelian "epicycles" to this, but I think first-order approximation is good enough, myself).

--The Sigil (B.S. in Astrophysics)

 

[fusangite]

Setting up my Aristotelian cosmology here...

Given that:

1) The visible planets are all approximatly the same size as Earth.
2) The apparent size is the same as here.
3) The apparent brightness is the same as here.
4) The solar system is Earth-centric.

How far away are the respective planets?

I only use Aristotelian cosmology in my games and this has never come up. Why? Because the sublunar sphere (and all others) are made of impenetrable quintessence.

I know the Ptolemy did indeed make these calculations. I know the distance to the first sphere (the lunar) was calculated to be almost exactly what we have since discovered it to be but I really don't know the distance to the other spheres that are farther out.

Of course, these other planets were not considered to be inhabited. Generally, they were classed as sun-like rather than earth-like. The idea of inhabited planets didn't really get going until Galileo broke the spheres. Prior to this, each star was associated with one or more specific angels which were considered to be consubstantial, to a greater or lesser degree, with the planet itself.

What do you need to know the distances for?

 

[Crothian]

are you setting up a Spelljammer game?

 

[Baron Opal]

Just want a couple of points of clarification:

1.) Are you trying to set up a cosmological model of the actual solar system (i.e., with "Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, X" as your planets?

Yes, although just the visible planets. Preferably in a Moon, Sun, Mercury, etc. order, but I'll take what I get.

2.) Per your point #1 - is "Jupiter" not REALLY a gas giant but actually the same size as earth?

Correct. I am assuming, however, a 50-200% variation on size based on real world size. So, Mercury is going to be half the size of Earth and Jupiter will be twice the size. Any actual correspondances will be completely accidental. Let's me play with gravity rules if/when the PCs visit.

3.) The apparent size being the same - I presume you want the same approximate arcseconds in the sky (e.g., Mars is about 20 arcseconds at closest approach). For the naked eye, this won't matter much though - planets are more or less "points."

Correct.

4.) Apparent brightness same as now - okay. Can "fiddle" with that.

5.) Earth-centric... do you include Sol (the sun) as orbiting?

Yes, see above. I am not wedded to the concept of the Sun being Earth sized. I would rather that the Sun and Moon don't have the same orbit even thought they have the same apparent size. The Sun is much brighter, however.

6.) Is a "first order approximation" (with perfect circles for orbits instead of ellipses) okay?

Circular orbits are fine. Even preferred, actually.

 

[Thotas]

Huh? Planets are points? Well, at my age my eyesight isn't what it was, and I live in the city now that I'm an adult, so there's light polution like crazy but ... as a kid, I read that you could pick out a planet among the stars by virtue of the fact that it was a (very small) distinct disc, rather than a point that twinkles. Testing this, it proved to be true.

 

[Baron Opal]

I only use Aristotelian cosmology in my games and this has never come up. Why? Because the sublunar sphere (and all others) are made of impenetrable quintessence.

What do you need to know the distances for?

Ehh, you can sail through the epicycles on the etherial winds.

I'm thinking of making the other planets different planes in their own right. I noticed that as I was designing my own planar cosmology a similarity between them and the energies of atomic shells came to mind. And, Aristotelian cosmology has a rather atomic aspect to it. Then, I happened to see a graphic of the Kaballic Tree of Life that was drawn with a number of circles with the Ein Soph outside, which reminded me of the shell of fixed stars. So, hopefully, I can get some number on Aristotelian cosmologic distances which will jibe with what i know about electron shell densities and the planets match close enough with the Kaballic sephiroths (sp?).

Add Arcana Evolved and Beyond Countless Doorways and stir.

 

[lgburton]

sephiroth is plural already

 

[fusangite]

Ehh, you can sail through the epicycles on the etherial winds.

So there are no spheres? Just circular orbits? That's fine but not actually Aristotelian.

Aristotelian cosmology has a rather atomic aspect to it.

I don't know what you mean by this.

So, hopefully, I can get some number on Aristotelian cosmologic distances which will jibe with what i know about electron shell densities and the planets match close enough with the Kaballic sephiroths (sp?).

That sounds fascinating. I hope it works out. I'm not sure where to direct you for the distance calculations made in the geocentric system; you might have to go back to primary documents from the middle ages or the original text. But at least some of the distances may be covered in history of science textbooks or anthologies.

 

[Baron Opal]

So there are no spheres? Just circular orbits? That's fine but not actually Aristotelian.

Oh, there are spheres. It's just that there are navigable holes where the epicycles jiggle the planets in their orbit. And, as they are invisible and indestructable, you have to have a crack mathematician who can calculate where they are. Otherwise you go splat and fall all the way back to Earth.

And, by atomic, I'm refering to the scheme where atoms have a descrete center (Earth / Nucleus) and then the orbiting masses (Planets / Electrons) traveling in distinct regions (Crystal Shells / Electron Shells). At the moment, I'm thinking of having each planet being a mini-transitive plane or the top layer of a plane. The number of layers is equal to the ideal (noble) number of electrons for that atomic shell.

Also, I've seen drawings of multiple Trees of Life where each iteration is farther and farther away from God. The qlippoth get involved here, and I'm not too sure what it / they are. So, by travelling up through the crystal shells and finding the Crown sephiroth, which is the exit point (say, Polaris) to the next iteration of the Tree. That gets you to the next atomic nucleus / Earth / what have you. So, you could eventually sail your way to the Prime Mover if you have the wherewithal.

Of course, I could never expect the players to figure this out, so this is mostly for my own amusement. And, I could never fill out all of the detail. It would take far too much time.

But, it's fun for me. And by the time my PCs get to the point when they are interested in planar travel, I'll be ready.

Edit: Oooh, each plane could be a moon... Hmm...