Earth in BSG
Fans of the show often ask, "what will Earth be like when they find it?" Ronald Moore always refuses to answer that question, and at times he suggests he has not even fully decided what form it will take. However, there is a fairly strong case to be made that, unlike the original, this show is set many thousands of years in our future, and that Kobol is a colony of Earth, not the other way around as told in the colonial mythology. There probably never was a 13th tribe that went to Earth. Instead, that story is a myth to cover the reality.
The original series in 1978 began with an introduction said to the audience: "There are those who believe that life here, began out there, with tribes of humans who may have been the forefathers of the Egyptians..." And indeed, by the end of that series, and in the dreadful sequel in 1980, it was revealed that the show was set in current times. That, however, was then, and this is a re-imagining with many key differences.
Adama says that "Life here began out there" is the first line of the Sacred Scrolls, and indeed for the colonials this is true, they come from Kobol. But where did life on Kobol come from? As the first line of the scrolls, there is a strong argument it was written on Kobol, from a Kobolian perspective, pretty much declaring in the miniseries that Kobol is a colony.
Clues in the show
The show actually gives us several clues. Most important is the scene in the Tomb of Athena on Kobol. In that scene, they see a projection showing all the constellations of the real Earth Zodiac. We're told those star patterns appear on the flags of the twelve colonies. We're also told the 12 tribes had older names which match the Earth names of the Zodiac. Starbuck says "they looked up and saw their twelve brothers," a line which upon further analysis makes no sense. The names themselves don't tell you a lot but the star patterns are an absolute giveaway. Why would 12 tribes chose as emblems for their flags star patterns only seen from the mythical planet of a barely remembered and lost 13th tribe? Indeed, the very fact that they have a story of the tribe on Earth requires that ships went from Earth to Kobol, and does not require any travel in the other direction. Later, when Starbuck goes to Earth, she photographs the Zodiac and confirms that it matches.
So Kobol's twelve tribes took their flags and names from the Earth sky. You can come up with convoluted explanations of how a 13th tribe went to Earth, then came back to Kobol and brought their new culture with them, and this culture then took over Kobolian culture so that its symbols became the symbols of the other tribes. But frankly, that just multiplies entities far beyond necessity. It's far simpler to accept that the culture originated on Earth and moved to Kobol.
If that's not enough, there is a clincher so strong in the same scene that is so absolute we almost wonder if it's a writing error. Adama sees the Lagoon Nebula in the simulated Earth sky, and recognizes it. The Lagoon Nebula is about 4,000 light-years from us, in the direction of the galactic center. But the kicker is that Adama calls it "M8." This (short for Messier-8) is an 18th century catalog designation for the Lagoon, well known to astronomers. This is not simply a translation of English into whatever language the colonials speak, this is a catalog number. The only way Adama could know the Lagoon as M8 would be if this takes place in our future.
Elosha, a priestess in the show gives a lesson to Laura Roslin about the book of Pythia. It is these books which tell the (false) story of Earth, but Elosha also relates that:
...in the sacred scrolls. 3,600 years ago, Pythia wrote about the exile and the rebirth of a human race: "And the lords anointed a leader to guide the caravan of the heavens to their new homeland and unto the leader they gave a vision of serpents, numbering two and ten, as a sign of things to come."
This story of exile and rebirth, written in the past tense 3,600 years prior indicates a third exodus, which strongly suggests Kobol is not the original world but the site of the described rebirth.
They also have a lot of legends of Earth, including books with pictures of Earth cities and a Temple of Aurora -- which they find in the ruins when they get to Earth.
Zoom to Earth
At the end of season 3, right after Starbuck says she's been to Earth, the camera pulls out of the galaxy, and then back in at essentially the same place. From there it zooms to the real Earth. And for those noticing, it's a present-day or later Earth, because it has the current Mississippi delta lobes, which are only a few hundred years old. (However, that is probably simply because they used a current photo.) However, what this does tell us is that Starbuck has been to the real Earth, and it's nearby, not an illusion or vision.
The biggest clue, however, comes from reality. We viewers all know that Earth is the real home of humanity, and was not colonized by people from another planet. We knew this in 1978 as well, but there was just the smallest shadow of a doubt back then to allow Glen Larson to get away with that plot. That doubt has since been erased.
It's been erased because we have learned to decode DNA, and we've developed a new system of classifying and understanding the tree of life which we call cladistics. DNA shows us that all life on Earth is related. All the other life forms on Earth share lots and lots of DNA with us. You are actually quite closely related to a mushroom -- much more closely related than you would be to any alien being. So while we only have several thousand years of written human history, our relationship to all the other life shows that we -- by which I mean we and our ancestors -- have been on this planet for at least 3 billion years.
(If that's too much for you, consider that all primates, including us, need to eat vitamin C to live, while other animals generate it internally. We and many of our cousin primates have the same copy of the gene you need to produce vitamin C internally -- but it's broken. Broken in just the same way. So it's just not possible that we would be the result of a different evolution than our monkey cousins.)
There are people who theorize that our ancient single-celled ancestors may have come from space, on Mars rocks or similar, but that's 3 billion years ago. Our planet is full of fossils and other records that trace our history back through those billions. If humans were the result of a colonization 10,000 years ago, we would not share all the DNA with the mushrooms and other life forms that have without question been here for billions of years.
So no, life here did not begin out there, at least not at the multicellular level. Nobody doubts this in the scientific community today. Creationists, who try to pretend the universe is 6,000 years old, doubt the fossil record but they are not taken seriously. And even they agree that this is the homeworld of humanity.
RDM has stated he wishes to write BSG as naturalistic science fiction. That means he won't contradict established science if he can avoid it. And here he can so easily avoid it. While a writer can write their story any way they want, the old plot of the original BSG was fantasy, not SF. In the old days, an SF writer could write a story about Mars with canals and an ancient martial race. Then science improved and probes went to Mars. Today, a writer could write such a story, but nobody would consider it SF. It would at best be a romantic fantasy, harkening back to more innocent days when we knew less about Mars. Indeed, when Moore declared he wanted to reimagine the BSG story as more realistic SF, the two most obvious things he needed to change was the poor sense of distance and speeds in interstellar travel, and the "Earth as a colony" notion. He (mostly) fixed the first one right away, the fixing of the other one is left as a surprise, it seems.
Moore, in his blog, was asked how he would reconcile reality (humans evolved on Earth) with BSG's original story.
A: I don't have a direct answer for this question yet. There are a couple of notions rolling around in my head as to how we reconcile the very real fact of evolution with the Galactica mythos, but I haven't decided which approach to take. However, it was a fundamental element of the original Galactica mythos that "Life here began out there..." and I decided early on that it was crucial to maintain it.
His answer appears to be that for the colonists, life here did begin out there, and that they believe that Kobol is the homeworld. However the fact that he addressed this question in his writing, and was dedicated in staying as true to scientific reality, should be answer enough.
Sometimes I am asked, "couldn't this be an alternate reality, an Earth which, unlike ours, is populated with space colonists?" It could. But realize that this would be an alternate reality where the "split" from reality goes back billions of years, not thousands. It would not have any of the same people, nations or history as our planet. Our planet is full of fossils -- this one would be empty, just as Caprica is presumably empty. All of our history would be different. Real humanity consists of various ethnic and racial groups which spread around the world anywhere from 100,000 to 12,000 years ago.
On real Earth, sub-saharan Africans are black. First Nations ("native americans") are Asian-derived, and got to the continent at least 12,000 years ago. Native Australians are black but highly different from Africans and made the trip 50,000 years ago. (There seem to be only a tiny number of black people in the fleet, too.) There's just no way to explain our history in terms of a set of colony ships arriving 4,000 years ago. So this would have to be a completely different planet. Thanks to the Creationist-vs-science debate that has raged in the USA for many years, it's safe to say that the "Ark" theory, which has Earth "colonized" recently, is perhaps the most debunked theory in history.
In other words, colonization by Kobol is very clearly not in our past. It could be in the past of a very different fictional Earth that bears no resemblance to ours historically and culturally and racially. I have written a more detailed analysis of this issue.
But in that case, what's the point? It removes all the relevancy to our own story, which is the whole reason to play these characters out as seeking Earth. Why bother have them seek Earth that bears only a geographic resemblance to the real thing?
Of course, what turned out to be the case was an alternate-reality Earth that is largely Earth in name only. A planet founded by Cylon colonists, where All Along the Watchtower was written by Anders, not Dylan. Where this planet has things from the real version of Earth, it would not be for any scientific reason, but rather simply as an act of author's fiat. As such, more a fantasy or allegory than the real planet. I think this is a terrible shame, but I'm not the show-runner.
Some have suggested that the show could present a human colonization of Kobol in the distant past, through an ancient Earth civilization (ie. Atlantis) which then fell. That's a workable plot, but there is no record of this civilization. It would have to have erased all record of itself, not just from Earth but from the Moon and Mars. This is a spacefaring civilization, and while you can imagine its Earthly remnants being covered over, this would not happen to anything they built on the Moon. And of course they would have built things on the Moon. So I rate this as a stretch. To use Occam's words, it multiplies entities beyond necessity in order to shoehorn a plot that really isn't all that novel or interesting.
Others propose that aliens could have abducted humans long ago from Earth and put them on Kobol. Possible, but RDM has declared he will not include aliens in this show, nor time travel, and I applaud both decisions. And again, to what purpose would he write such a plot. Just so he can duplicate Galactica 1980? We know he doesn't want to do that.
Trip to Earth or from Earth?
The colonial sacred scrolls tell what is surely a lie in our universe -- that there was a 13th tribe that colonized Earth, 2000 years before the tribes left Kobol on their own. So they assume they are following a trail left on a journey from Kobol to Earth. That's not impossible, presuming there was 2-way commerce for a time. But their scrolls tell of the tribe landing on Earth, which thus requires at least one trip from Earth to Kobol to get the message through.
The fleet presumes the trip was to Earth, but that's quite odd. For example, once they see the nova explode in Rapture, they imagine the mandala was left as a signpost to identify the Ionian nebula. But if you're out hunting your new home, you don't know exactly which direction you're going. It makes much more sense to leave a trail of clues behind you pointing to where you came from rather than clues about where you are going -- especially if you don't know where you're going yet.
The concept of a "lost 13th tribe" comes from Mormonism. Glen Larson, who wrote the original BSG story, was a Mormon and based many of its aspects on Mormon legends, including this tribe. There is no particular reason Ronald Moore, who is not a Mormon, would wish to stick to that story when it makes no sense in the context of modern science.
What will Earth be like?
Even knowing this is set 4,000 years or more in the future -- which makes it more relevant to us, I believe -- there is still a lot of freedom for the writers. Earth could be an advanced world. It could be a world that expelled the Kobolites. It could be a dead world, like Kobol. It could be a world that fell and rose again to whatever level of technology the writers desire.
Update: We seem to have come to a ruined Earth, which was one of the scenaria I thought fairly likely, though it looks like it was ruined much more recently than 3,600 years ago. This suggests that Earth has risen and fallen, with the most recent fall perhaps a few hundred years prior. Rumours suggest it has inhabitants we will see at the end of the series.
The recent trip of Starbuck to Earth does put some constraints on this. See the previous post for more details.
New clarifications have arrived. The Rebel Hybrid declares that "The Five" are "From the home of the 13th." While her use of the term "the 13th" seems to contradict the thesis that there was no 13th, from the point of view of the colonials and S7 Cylons, that is how they know them and it makes sense in her little number-poem. However, the ancient Final Five are from Earth, another sign it's the origin of all these people and technology.
The song, "All along the Watchtower" has provided confusing signals. Some hints from staff say it's just a song. Others say it is the real Dylan tune. This is in line with the Final Five being from Earth, and having been born/created in the 21st century. Taken literally, this insists the show is set in our distant future. However, hints from Moore are ambiguous but he does say the song is intended to show a connection between our Earth and their world. He has also said there is a reason the props and sets look Earth-derived; it is intended to show the connection between the colonials and us.
And of course in Revelations we arrive on the target planet, almost surely Earth. It's in ruins but once held a civilization. Many people feel the images suggest they are sitting in Brooklyn, but that can't be confirmed yet. Whoever controls the triggers of the Final Five and who took Starbuck wanted them to go there, joined with the Cylons.
If it is not Earth, and just another colony, it doesn't say much to us that it's in ruins. It's just a sad story, that this trip was a waste. It makes much more sense in the context of Earth as the ancient home, and of a repeating cycle of man-machine war and exodus, starting here, with the most ancient Cylons from here.