What would be the possiblity of galaxy sized planet of sorts for a table top roleplaying game

Question

Hello and thank you for reading this, hope your doing well today.

This is difficult to describe, but I will do my best, please bear with me.

Imagine a table that's oval shaped, minus the legs. Christmas lights are suspened over the table but only an inch above the surface

but its big, imagine an elliptical galaxy (which is where I got the idea)

This plane/planet is a creature/god, capable of modifying many laws of physics. Ideally not all though. the Christmas lights suspended above the table are stars. The table itself is land.

1. I assume that much mass would just collapse naturally into a black hole ? That's why the slight laws of physics changes

   2. The table itself is on a galactic level is thin. maybe 300 miles deep at its deepest part. mostly magma filled, but there are "cold spots" were people and can climb down and emerge on the other side of the table/planet

   3. Right smack in the middle is the gravitation plane once you pass through it gravity reverses so people on the underside of the table aren't being pushed away from the plane/planet. layered in like the cheese in a grilled cheese sandwich

   4. Weather over the plane. Imagine soap suds on a table, some bubbles are bigger and they have mild climates, the smaller ones are more likely to be stormy/uninhabitable. The smallest ones are the size of a continent the biggest ones the size of a solar system

   5. The purpose of this world is to allow players to explore vast uncharted areas with simple technologies like sailing ships.

   6. I have no idea what a world with no curved horizon would look like, I have told the players that you can only see through so much air before it becomes opaque

   7. Night as I explained it happens in 36hour cycles where the sky just seems to get darker like those glasses that turn into sun glasses. Most area is dark lands, where no star light reaches, that's where ferocious critters live.

   8. Gravity is pretty consistently 1g. I want it to be weird, but no so weird they can't understand it.

   9. if it matters the creature/god itself is dispassionate simply studying the effects of things in their habitat looking for evidence of other beings like itself. the creatures that live on it are facsimiles of creatures from other galaxies. For people and animals it reads their mind and genetic structures then creates a clone that wakes up in this strange new world. IE Tom Burk in 1913 april 3rd Chicago goes to bed that night the plane scans his mind implants them in a facsimile(clone) so which wakes up on a new world very confused. Mean while the real Tom Burk wakes up and goes to work the next day.

   Questions.

   1 Am I going to have to use "magik" to explain almost everthing (the players just think they are on a very big planet at this point, they don't know the "planet" is sentient either.)

   2 Given the thickness of the planet, could it actually be 1G ? or by necessity does it have to be "magik" that keeps it from being 78,000 g's or something like that.

   3 General thoughts, stuff I should be explaining but am not. anything is welcome.

   Thanks for reading.

Answer 1

A galaxy-sized flat piece of earth seems a bit of an overkill if you just want your RPGers to have vast tracts of unexplored land.

1. Our milkyway has a diameter of 100,000 lightyears and a height of about 2,000 lightyears (according to Wikipedia). A single lightyear is a distance of 5.88+e12 miles (5,880,000,000,000 miles or 9,460,000,000,000 kilometers). Even if your RPGers were sitting in the fastest airplane currently known on earth (SR-71 Lockheed) at 3.5 times the speed of sound, it would take them around 300,000 years to cross that single lightyear. And that only if they were flying at that top speed the entire time 24/7 and without breaks for refueling or repairing their airplane. Your RPGers are considerably slower, so they'd need several million years to cross even a single lightyear -- overkill. So, expanding your planet to galaxy-sized is just overkill. Waaaaaaaaaay overkill.

2. You'd have to use magic to explain everything. It starts with a special 1G gravity that somehow prevents people and atmosphere from falling off the outside edge (meaning a force pulling the edges towards the center) and yet doesn't mush your plane-planet into a round sphere. Then there is the entire galaxy around that 'planet' - the christmas light stars that dim and brighten on command to simulate a day-night cycle, the way they keep a safe distance from the disk although it's floating around like a fly-swatter in a hive of bees, etc.

3. Since you've got a disk instead of a normal rotating sphere, you won't get any magnetic field of your planet. Meaning no compasses, but worse -- no shield against hard space radiation and solar flares. Life on your planet would not have developed.

For more ideas on super-planets that are plane-like, have a look at dyson spheres and the questions about them (as a bonus, a dyson sphere neatly solves the problem of having an outside edge to fall off):

Is a solar dyson sphere habitable discusses the scientific necessities for creating a hollow planet sphere of a diameter of 16 to 50 light minutes (still really, really large enough to give your RPGers hundreds of thousands of years of exploring new territory)

How and when could a Dyson sphere civilization figure out the shape and size of their sphere? gives you an idea of what living on such a dyson sphere is like (including curvature of horizon).