Monty,
The answer is we don't know what gravity is. I suspect that when we really discover what gravity is, we may discover a new phenomenon of antigravity.
PS - dear moderator, pls to not label someone a crackpot who disagrees with your theories. When you can discover something for a fact, it is no longer a theory. Hence, most of what you tout is still theory, until you prove it, don't call someone who challenges it a crackpot.
I believe it is our duty to question everything until it is proven.