Long ago, the god of the soil and the goddess of the sea became lovers. Their union created the Ur-world composed of numberless islands in an endless sea. Upon these islands other creatures were born from the labors of other gods. These creatures grew and learned and prospered for countless generations, sailing upon the welcoming seas. After eons, after the rise and fall of hundreds of empires and kingdoms, Soil and Sea argued and rent the Ur-world asunder. The once-welcoming seas now stranded any that dared travel beyond the sight of land in a gigantic never-ending ocean upon which they died from privation. The once-interconnected islands were stranded alone, only able to communicate with other nearby islands, for a ship needed to keep some type of shore in sight to avoid the terrible fate of those stranded in the Forever Sea. Each island or group of islands became independent worlds set apart from their brothers. This new and terrible isolation lasted as along as the era before it, and many new creatures, new gods, and new peoples were born during the long separation.Right away the similarities are obvious. For the longest time people were unable to communicate with other distant islands which each developed its own unique culture, but now, through the use of voyager ships (the knowledge of which was given by a rogue God) the many peoples can once again interact. These two concepts are, IMO, very important to the flavor and feel of both games.
This age of isolation ended when an unidentified goddess, allegedly a daughter of Soil and Sea, taught the peoples the secret of taming elementals to create ships that could navigate through the Forever Ocean. She believed that a return to the first age would rekindle the affections that Soil and Sea once had for each other. Unfortunately, the discovery of her gift of knowledge was met by anger and rage by all of the gods, both new and old, and she was imprisoned in the sky, transformed into a cloud cursed to move forever against the wind. But the wondrous gift of Obstinate Cloud (as she is named by those who tell her story) could not be undone, and the peoples of the islands began to explore a newly boundless world in their strange voyager ships.
For ease of use, Traveller uses the term "World" when it means solar system and Worlds Apart uses the term "Island" when it means "a single island or group of islands that are all within sight of each other when sailing." Islands can have many different compositions, ranging from the size of a continent to a single small atoll, from a long peninsula of visibly-connected islands to a large archipelago. Using our world as an example, a single island could be Australia, the entire Eurasian/African super-continent, or the Hawaiian Islands. The diversity that can be encountered is grand.
It is this diversity that is integral in creating the Fantasy Opera feeling I'm aiming for with Worlds Apart. The possibilities are almost endless, and the GM is responsible for meshing all these things together. Imagine the great ports of our world throughout history - Carthage, Constantinople, Ostia, Malacca, Singapore, London, Calcutta, etc.. - but in a fantasy environment where trade is possible throughout a giant interconnected web of different civilizations and every conceivable difference of human appearance and dress. Now mesh this with the presence of non-human races, which although still few in number and rare in presence, add additional spice to an already powerful curry of adventure.
That's Worlds Apart. It's the unlimited spice palate from which a GM can create whatever meal he would like.