Battlestar Galactica was a series with no background. Very little time was spent thinking out the history and culture of the Colonies, and it shows. Tantalizing bits of information appeared in the scripts and were never further developed (and sometimes ignored or contradicted in later episodes). We know, for example, that the normal Colonial lifespan was 200 yahrens. What effect would such longevity have on people, on institutions such as marriage, on jobs, on birthrates? Having even more to lose if they died, would people be more cautious? Was Colonial society more fossilized because of the innate conservatism of the old? This is only one example. Yet in spite of their alien culture, the Colonials are transplanted 1970s Americans, right down to their hairstyles (one of the few things, I might add, that dates BG upon viewing 20 years later!).
Though the major background mysteries of BG are beyond firm solution, the minor ones are often worth trying to explain even now.
What was Aurora’s job before the holocaust? This is in fact very obvious, but no one else seems to have ever hit upon it; Aurora was a civilian shuttle pilot before the destruction, probably flying interplanetary or subplanetary shuttles. We know this because new shuttle pilots for the fleet are trained aboard the Galactica and had Aurora been so trained Starbuck would have learned of her survival long before their accidental meeting in “Take the Celestra,” either by seeing her during her training or hearing of her from someone else who knew of their relationship, as evidently a lot of Starbuck’s friends did (it was such an object of discussion that even Cassiopiea and Sheba have heard of it before Aurora reappears).
Another mystery, with far fewer useful clues, is what was Orion? Orion seems to have been a world separate from the Colonies, having at least two moons (Sheba uses the phrase “pale as an Orion moon;” her use of  “an” suggests more than one moon), its own currency (Orion checks), and its own manufacturing base (Siress Blassie’s energizer was made on Orion). It’s even pronounced two different ways; “Oh-ry-on” and “Or-ee-on.” Orion clearly was an important trading partner with the Colonies. But was it an ally planet inhabited by an alien race, or a human-settled world, an offshoot from the Colonies? From what little evidence there is in the series, we can’t even hazard a guess.
One subject there has been some disagreement about in fandom is the status of Tolen, the tall Pegasus officer portrayed by Rod Haase in “The Living Legend.” Apparently in an early draft of the script he was a flight officer, equivalent to Omega, and in the novelization he’s still a flight officer. But Cain in the episode addresses him as “Colonel” and his uniform is that of a senior officer, with two collar pins, compared to Omega, who had no collar pin in early episodes, and a single pin later. My feeling is that Tolen is a colonel, and Cain’s exec. When Cain is relieved of command, Tigh is placed over Tolen, as is to be expected, since Tigh is clearly the senior officer and probably has had actual command experience.
The Colonials had a holiday called Armament Day. Some of the more extreme British fans have tried to portray the Colonials as unfortunate pacifists caught in a war they’d rather avoid (in spite of internal series evidence that the Colonials actually started the war!), but anyone who celebrates their weaponry is clearly a lot more militaristic than some fans may prefer to believe.
Here’s one to ponder; was Baltar in the military? Charybdis, after all, addresses him as “Commander Baltar.” Was he once an officer who quit to go into “business” (with the Cylons and Ovions!), or was he cashiered? Here’s my theory, which I think fits rather neatly into the evidence in the series; Baltar was in charge of the military expedition that discovered tylium deposits on Carillon. He filed a false report with military intelligence and then resigned to go into business developing the deposits himself. He may have become a traitor after he left the military...or was he one before....?
Who were the Terrans? It’s always been obvious to me that Terra was a colony of Earth, but a lot of fans disagree. Admittedly Glen Larson is the only definitive source of information, and he’s not talking (and I might not trust his response at this remove), but the names, political situation, and even the cross Sarah’s father is buried under are suggestive. Galactica 1980 was a fluke and ought to be regarded as such. Had the Colonials found Earth it would have been Earth of the future, not the Earth of today or the past.
What kind of hyperlight drive did the Colonials use? Any time we see the fleet it’s in normal space, traveling at below the speed of light, and for the Galactica or Pegasus to approach light speed is apparently quite an event (as well it should be - check into a physics phenomenon called the Lorentz Factor sometime). Are we to assume that the Colonials had no form of faster-than-light drive? The production team (amongst whom was no one with a scientific or even science fiction background—something else that shows) appears not to have realized that the Colonials would need some sort of “warp drive” elsewise they would have gotten nowhere very slowly, and so they never mentioned an FTL drive in the series. But there is in-series evidence about the Colonial form of FTL drive. In fact, it’s a form of FTL travel used by large numbers of science fiction writers today because it seems at least remotely possible. Cal Tech physicist Dr. Dan Alderson developed the idea for Jerry Pournelle. He theorized that there are lines of force between stars along which nearly instantaneous FTL transit is possible. A ship has to be in precisely the right point in space to enter one of these ‘flaws.’ The ship arrives at the warp point, switches on its FTL drive, and reappears in another star system. All other travel is slower-than-light. Warp points are near stars, which explains why the Colonial fleet is usually in or near a star system; they’re searching for the next warp point! Therefore the Colonials, like Pournelle, McCollum, Bujold, Weber et al use the Alderson Drive. For more thorough explanation of the Alderson Drive, read “Building the Mote in God’s Eye” by Larry Niven and Pournelle in Pournelle’s A Step Farther Out. This form of travel could be the basis for a number of very interesting stories, so fan writers take note. Not to mention whoever does the eventual BG revival....