Perhaps I am confused by theories, but wasn't the idea of the shape of the earth once a scientific theory? What was once a scientific theory is no longer a theory.

to Buddhism "false" is included in the definition of concept — khaled

But Buddhists' have a concept of not-self and unconditioned existence. Would they deny the truth of these concepts or are these somehow not concepts?

Such a world is impossible because we'll never know for sure we discovered how gravity works. — khaled

Can you elaborate on this? Why can't there be a possible world where we can know that we understand gravity?

I understand that a Buddhist would not be concerned with such things. I also accept that the theories we have of physical phenomena are simply that, theories. Yet, if we were to affirm a theory and fully understand the interactions of whatever creates gravity and things like gravity, then we would no longer be applying a false concept. I only use the concepts we have now because that is the language I have available.

In a possible world where we discover how gravity works, we would no longer have a false concept that supervenes on what is occurring. Instead we would have a true (albeit incredibly complex) concept of a phenomena; a concept that would not change. If this is possible, then wouldn't all fundamental things be necessarily unconditioned?

I believe this additionally would not work for non-fundamental things such as chairs and people because no clear concept of such a thing seems viable as they truly are man-made concepts. Ignoring our concepts of gravity, there really is something fundamental that exists, be that gravitons or whatever future theory comes down the line. Does this fundamental phenomenon exist beyond words (like paranirvana (and space according to Wayfarer)) and is thus unconditioned?

Buddhist philosophers do consider the notion that space is an ‘unconditioned dharma’ — Wayfarer

Doesn't space consist of a web of particles (though these particles are far apart and have very little mass). This would mean that space as we know it is also constantly changing (also seen in the overall expansion of the universe) and would thus be conditioned. I think I would agree that the actual empty areas between those particles in space would appear to be unconditioned and that's probably what you are talking about. I am still curious as to what other non-phenomena(?) could be considered as unconditioned.

Buddhism is about NOT trying to forcefully explain the world — khaled

Even if they aren't trying to explain the world and they view conceptions as illusions that supervene over the reality of what make up aggregates, I am still curious as to what the metaphysics of such illusions would look like. Additionally, you mentioned that gravity does undergo change. I guess my question is this:

Buddhists view our concepts as false because our concept of 'chair' is actually an aggregate of wood and metal. These are also aggregates that can be broken down further and further until we get to the subatomic area of business that consists of particles with mass (proton, neutron, quarks). There are also things like photons (and most likely gravitons) that do not have mass. Our concepts are wrong and illusions because the thing we are actually gesturing at (chair, water, bed) is an aggregate of smaller things and all these things are constantly undergoing change and will always one day become something that no longer resembles what we originally saw. However, our concept of gravity (if we were to get it right) is not something that changes because although gravitons move around, they are not telling an incorrect picture. If gravity is the interactions of gravitons then the picture of gravity is potentially not an illusion. Physical objects supervene on particles. Forces don't supervene on their particles? This is what makes me think that the hypothetical Buddhist who is concerned with metaphysics would consider gravity unconditioned.

There is no such thing as ‘non-mental phenomenon’ — I like sushi

Consider that all physical and mental phenomena are conditioned. Though messy, my asking if gravity was a non-physical, non-mental phenomenon was my asking if gravity is unconditioned by their definition. A non-phenomenon doesn't exist or it would be a phenomenon. Yet unconditioned things seem to fall into this category.

Since materialness leads to 'delusions' of selfhood and therefore suffering I feel that Buddhists are concerned with physical things in that they don't want you to be disillusioned by them. Also, even if physical things don't actually exist they would still have a metaphysics based around such illusions of phenomena.

Every physical phenomena is impermanent under Buddhism; this is what makes material things conditioned. I have considered gravity to be a physical phenomena yet it appears to be permanent in that it is never altered (much like strong and weak nuclear forces perhaps). If I'm making sense, does this mean that gravity is a non-physical, non-mental phenomena? Or is it impermanent in some way that I'm not seeing?