I'm one of those world builders that begins with core ideas from which to create many possibilities. Frankly, it can give me a wicked headache sometimes.
For the sake of simplicity, we'll call this universe Maderia. (It's a Spanish dessert wine.)
In Maderia, the following facts define the universe:
Sound requires a medium to travel through. It is usually air, but like our universe, it can be anything. Also, the denser the medium, the faster sound travels through that medium.
Light also requires a medium to travel through. It is the luminiferous aether. The aether has a constant velocity (thus no color shifting of stars in the sky) except where aether rivers exist.
Aether rivers are wide currents of denser aether with varying speed and direction. They are analogous to water rivers. These aether rivers shimmer the colors of the rainbow. Aether rivers go through a planet and do not pool.
Magic also requires a medium to travel through. This would be the catalytic reagent. The reagent has no prime moving force behind it. Only those that use magic can move reagent from one place to another. Like other mediums, it exists in varying densities. Where reagent is more dense, mages can move more magic. In other words, cast more powerful spells.
For clarity later on, a vacuum is the absence of all matter , but not necessarily an absence of aether and/or reagent. An aether vacuum is the absence of aether and matter, but not necessarily reagent. A reagent vacuum is only the absence of reagent. A true void is the absence of all three.
Next post, the progression of Science.