PY: I’m aware of how solid the theory of gravity is, and I have little reason to believe that it will be uprooted and replaced. I’m just making the point that we may be wrong about everything we know.
Let me give you an example. Before we sent rockets to the moon (yes, I believe we did), no one had ever seen the “far side” of the moon (again, this is assuming that everything we believe is correct). But we had bounced radio signals off of it, and they returned to Earth. Did that prove that the moon was a solid object or not?
Now let’s assume that when that first rocket ship circled the moon, we discovered that there was no far side of the moon. Let’s say that the photos from behind the moon showed Earth. What would that say about our science? It would say that we need to relearn some of what we call physics. Because physical science attempts to explain reality. Where it is contradicted by reality, science must change.
Before you get hung up on how my example is impossible, let me remind you that we have an object that we are all familiar with which has no “far side”. When standing behind it, you cannot see it at all. It is called a rainbow. And no – you cannot bounce radio waves off of rainbows – but that does not mean that a similar object cannot exist in this world which has those properties. Physics does not define the world. The world defines physics. If we find something that contradicts gravity, gravity goes out the window (I wonder if it would fall, though).
Getting back to the main topic. We have no reason to disbelieve gravity right now. But we could find one at some point. And that is just one example of a building block of science that if completely uprooted would change everything we have “proven”. Maybe it is not gravity that we are wrong about, but if we are wrong about ANYTHING, then our proof that the Earth orbits the Sun would be shattered.