For better or worse, JJ, the Captain's wife and crew member extraordinaire, is a sci-fi fan. She saw this article from a site called TV Tropes and thought other sci-fi fans might get a 'Big Bang Theory' out of it...
Maybe it's the romance, maybe it's the adventure, maybe it's the obvious parallels to the Age of Exploration, but for some reason, when people write about space, they tend to make parallels to the sea, as President Kennedy (himself a former naval officer) did in his "Space is the new ocean" speech. Often, it goes far beyond metaphor. Science Fiction writers frequently use nautical analogies for pretty much everything in space, and fill in the gaps in their own knowledge about spaceflight with details specific to sea travel.
- Spacecrafts are often called "spaceships" and sometimes just "ships". In many series, a small spacecraft can even be called a "boat", and space-based missiles are in some stories called "torpedoes".
- Furthermore, the classes of ships in the Standard Sci-Fi Fleet are usually analogous to classes of waterborne ships, especially those used during World War II: Cruiser, Battleship, Destroyer, Frigate, etc. Good luck finding a Space Schooner or Space Canoe.
- Spacecraft even have "lifeboats"—generally called escape pods or something similar—despite the concept being largely impractical in case of realistic space travel.
- Some works of fiction blur the line between spaceships and oceangoing vessels even further.
- Space is two-dimensional. Viewscreens are almost always two-dimensional, when displays for battles at least should be three. Spaceships may also have navigation lights like sea ships: very useful for gauging another ship's orientation in 2-D, but useless in 3-D.
- Space has friction.
- Space militaries almost always use naval ranks, as opposed to army ranks or the RAF system, and soldiers stationed in space are usually called "marines", e.g. the "space marines" of Aliens, Doom, Marathon, Starcraft, etc. Starship Troopers did not call its soldiers marines though it could be argued that it established the archetype for later space marine forces. Even in real life, space explorers are called "astronauts" and "cosmonauts".
Intrigued and you would like to read more?http://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceIsAnOcean