Here's a couple dumb questions that shouldn't be too plot-important:
Does the Physical Realm of the Cosmere have more or less the same structure as our own? It's obvious from Mistborn that solar systems function as they do in our universe, but it's less obvious if there are galaxies, clusters, superclusters, and so forth. Are there?
If the Cosmere does have the same structure as our own, are the Shardworlds all in the same general area (a galaxy, for example), or are they completely spread out?