First of all, I ask you not to tell me how to answer questions since you have answered none of mine, despite my insistance to do so.
Secondly, all that I admitted to was the wrong choice of words - "based on" rather than "rely upon" (excuse my limited knowledge of English) in light of your statement that the RE theory came before gravity was introduced (by the way, I found out information pointing out that gravity might have actually come into existence first, which could make half of this conversation obsolete - I am posting it below).
Now, to move to your questions,
No, we don't know what causes gravity and that was stated from the beginning of the conversation. We know that gravity exists, we know how it operates, but we don't know why it exists.
Gravity is what the RE theory "relies upon" - I sincerely hope we have no disagreement here since half of this thread was dedicated to word usage. Gravity is not part of the RE theory. It was NOT introduced into science IN ORDER to prove that the earth was round, but rather to explain the motion of planets in the universe. As people began to study the forces at work, they realized that using Newton's theory of gravitation they could explain the shape of our planet - call it a bonus if you wish. It is NOT a PART of the RE theory. Here are Newton's exact words to prove this:
I deduced that the forces which keep the planets in their orbs must be reciprocally as the squares of their distances from the centers about which they revolve; and thereby compared the force requisite to keep the Moon in her orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly.
Therefore, not knowing WHY gravity exists remains a question outside of the RE theory.
I think you should rephrase your third question - the wording is... ambiguous.
Now, consider for a second that what you said about gravity coming into existence AFTER the RE model was introduced is wrong... which would make your argument obsolete. Apparently, "Since the time of the Greek philosopher Aristotle in the 4th century BC, there have been many attempts to understand and explain gravity" (
http://en.wikipedia.org/wiki/Gravity). Now, if that's true, then the RE theory could be said to be BASED on gravity, rather than RELYING upon it. It's open to debate: which came first, the chicken or the egg? Honestly, it doesn't make that much of a difference to me if you say that the RE theory is based on gravity or relies upon it, since either way gravity is one thing, and the round earth another.
What is interesting to note is that the whole point of this debate sprang from the fact that I wanted (and I believe I did) prove that the RE model leaves no unanswered questions, such that when math no longer offers an answer (for example, the reason why gravity exists) observations STILL do. What I wished to say but did not get a chance to until now is that there are NO observations or axioms or whatever you want to call them for the FE model. For example, what kind of observations/proof do we have that the government has been hiding the true shape of the earth for hundreds of years? What observations/proof do we have that show the Sun as a big light that turns on and off rather than a rising and setting body in the sky?